Datasheet · 2023

TI TPS2550 / TPS2551 Adjustable Current-Limited Power-Distribution Switches — Datasheet (SLVS736C)

Adjustable current-limited switch; also the source of the USB 2.0 power rules quoted (100 mA, 44 Ω ‖ 10 µF).

Author: Texas Instruments
Year: 2023
Type: Datasheet
Credit: Texas Instruments (ti.com)

usb
current limit
power switch

TPS2550, TPS2551 SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 TPS255x Adjustable Current-Limited Power-Distribution Switches 1 Features 3 Description • • • • • • • • • • • • The TPS2550/51 power-distribution switch is intended for applications where heavy capacitive loads and short-circuits are likely to be encountered, incorporating a 100-mΩ, N-channel MOSFET in a single package. The current-limit threshold is user adjustable between 100 mA and 1.1 A via an external resistor. The power-switch rise and fall times are controlled to minimize current surges during switching. Adjustable current-limit, 100 mA–1100 mA Fast overcurrent response - 2 μS typical 94-mΩ high-side MOSFET (DBV package) Reverse input-output voltage protection Operating range: 2.5 V to 6.5 V Deglitched fault report 1-μA maximum standby supply current Junction temperature range: –40°C to 125°C Built-in soft-start 15 kV ESD protection (with external capacitance) UL listed – file No. E169910 Current-limit resistor calculator – SLVC163 2 Applications • • • • • USB Ports/Hubs Cell phones Laptops Heavy Capacitive Loads Reverse-Voltage Protection The device limits the output current to a desired level by switching into a constant-current mode when the output load exceeds the current-limit threshold or a short is present. An internal reverse-voltage detection comparator disables the power-switch in the event that the output voltage is driven higher than the input to protect devices on the input side of the switch. The FAULT logic output asserts low during both overcurrent and reverse-voltage conditions. Package Information PACKAGE(1) PART NUMBER TPS255x (1) BODY SIZE (NOM) SOT-23 (6) 2.90 mm × 1.60 mm WSON (6) 2.00 mm × 2.00 mm For all available packages, see the orderable addendum at the end of the data sheet. TPS2550/51 5 V USB INPUT USB Data 0.1 mF USB Port OUT IN RFAULT 100 kW 120 mF * FAULT Signal FAULT ILIM Control Signal EN GND RILIM 15 kW PowerPAD * USB Requirement that downstream-facing ports are bypassed with at least 120 mF per hub Figure 3-1. Typical Application as USB Power Switch An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 Table of Contents 1 Features............................................................................1 2 Applications..................................................................... 1 3 Description.......................................................................1 4 Revision History.............................................................. 2 5 Device Comparison Table...............................................3 6 Pin Configuration and Functions...................................4 7 Specifications.................................................................. 5 7.1 Absolute Maximum Ratings........................................ 5 7.2 ESD Ratings............................................................... 5 7.3 Recommended Operating Conditions.........................6 7.4 Thermal Information....................................................6 7.5 Electrical Characteristics.............................................6 7.6 Typical Characteristics................................................ 8 8 Parameter Measurement Information.......................... 11 9 Detailed Description......................................................12 9.1 Overview................................................................... 12 9.2 Functional Block Diagram......................................... 12 9.3 Feature Description...................................................12 9.4 Programming............................................................ 13 10 Application and Implementation................................ 15 10.1 Application Information........................................... 15 10.2 Typical Applications................................................ 15 10.3 Power Supply Recommendations ..........................19 10.4 Layout..................................................................... 20 11 Device and Documentation Support..........................22 11.1 Receiving Notification of Documentation Updates.. 22 11.2 Support Resources................................................. 22 11.3 Trademarks............................................................. 22 11.4 Electrostatic Discharge Caution.............................. 22 11.5 Glossary.................................................................. 22 12 Mechanical, Packaging, and Orderable Information.................................................................... 23 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision B (November 2008) to Revision C (October 2023) Page • Added GPN to beginning of title..................................................................................................................... 0 • Updated the numbering format for tables, figures, and cross-references throughout the document................. 1 • Changed the high-side MOSFET resistance to 94-mΩ...................................................................................... 1 • Moved the Device Comparison table..................................................................................................................1 • Added a Package Information table, and removed the General Switch Catalog table.......................................1 • Changed this section title to "Device Comparison Table" and reorganized so that it follows the Revision History section.................................................................................................................................................... 3 • Changed this section title to ''Pin Configuration and Functions'', and added a pinout drawing before the Pin Functions table................................................................................................................................................... 4 • Updated the ''ESD content'' and the mark message...........................................................................................5 • Added ''ESD Ratings'' section.............................................................................................................................5 • Moved topic to follow the ESD Ratings section.................................................................................................. 6 • Changed this section title to ''Thermal Information''............................................................................................6 • Moved topic to follow the "Thermal Metrics" section.......................................................................................... 6 • Added ''Functional Block Diagram'' section...................................................................................................... 12 • Added ''Device Functional Modes'' section.......................................................................................................13 • Added the ''Design Requirements'' section.......................................................................................................15 • Added ''Power Supply Recommendations'' section.......................................................................................... 19 • Added ''Layout'' section.................................................................................................................................... 20 2 Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 5 Device Comparison Table DEVICE TPS2550 TPS2551 (1) (2) AMBIENT TEMPERATURE(1) –40°C to 85°C ENABLE SON (2) (DRV) SOT23(2) (DBV) RECOMMENDED MAXIMUM CONTINUOUS LOAD CURRENT Active low TPS2550DRV TPS2550DBV 1.1 A Active high TPS2551DRV TPS2551DBV 1.1 A Maximum ambient temperature is a function of device junction temperature and system level considerations, such as power dissipation and board layout. See dissipation rating table and recommended operating conditions for specific information related to these devices. Add an R suffix to the device type for tape and reel. Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 3 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 6 Pin Configuration and Functions OUT ILIM FAULT 1 2 3 PAD TPS2550/TPS2551 DRV PACKAGE (TOP VIEW) 6 IN 5 4 GND EN TPS2550/TPS2551 DBV PACKAGE (TOP VIEW) IN GND EN 1 2 3 6 OUT ILIM FAULT 5 4 EN = Active Low for the TPS2550 EN = Active High for the TPS2551 Table 6-1. Pin Functions PIN NAME 4 I/O DESCRIPTION TPS2550DBV TPS2551DBV TPS2550DRV TPS2551DRV EN 3 – 4 – I Enable input, logic low turns on power switch EN – 3 – 4 I Enable input, logic high turns on power switch GND 2 2 5 5 IN 1 1 6 6 I Input voltage; connect a 0.1 μF or greater ceramic capacitor from IN to GND as close to the IC as possible. FAULT 4 4 3 3 O Active-low open-drain output, asserted during overcurrent, overtemperature, or reverse-voltage conditions. OUT 6 6 1 1 O Power-switch output ILIM 5 5 2 2 I External resistor used to set current-limit threshold; recommended 14.3 kΩ ≤ RILIM ≤ 80.6 kΩ. PowerPAD™ – – PAD PAD Connect ground connection externally to POWER PAD Internally connected to GND; used to heat-sink the part to the circuit board traces, connect to GND pin. Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 7 Specifications 7.1 Absolute Maximum Ratings over operating free-air temperature range unless otherwise noted(1) (2) Voltage range on IN, OUT, EN or EN, ILIM, FAULT Voltage range from IN to OUT IOUT Continuous output current VALUE UNIT –0.3 to 7 V –7 to 7 V Internally limited See "Thermal Information Table" Continuous total power dissipation FAULT sink current ILIM source current 25 mA 1 mA TJ Maximum junction temperature –40 to 150 °C TSgt Storage temperature –65 to 150 °C 300 °C Lead temperature 1,6 mm (1/16-inch) from case for 10 seconds (1) (2) Operation outside the Absolute Maximum Ratings may cause permanent device damage. Absolute Maximum Ratings do not imply functional operation of the device at these or any other conditions beyond those listed under Recommended Operating Conditions. If used outside the Recommended Operating Conditions but within the Absolute Maximum Ratings, the device may not be fully functional, and this may affect device reliability, functionality, performance, and shorten the device lifetime. Voltages are referenced to GND unless otherwise noted. 7.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 Charged device model (CDM), per JEDEC specification JESD22C101(2) ±500 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 5 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 7.3 Recommended Operating Conditions VIN MIN MAX UNIT V Input voltage, IN VEN Enable voltage V/EN 2.5 6.5 TPS2550 0 6.5 TPS2551 0 6.5 0 1.1 14.3 80.6 kΩ 0 10 mA –40 125 °C IOUT Continuous output current, OUT RILIM Current-limit set resistor from ILIM to GND I/FAULT FAULT sink current TJ Operating virtual junction temperature DRV & DBV V A 7.4 Thermal Information BOARD PACKAGE THERMAL RESISTANCE θJA THERMAL RESISTANCE θJC TA ≤ 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C TA = 70°C POWER RATING Low-K(1) DBV 350°C/W 55°C/W 285 mW 2.85 mW/°C High-K(2) DBV 160°C/W 55°C/W 625 mW 6.25 mW/°C Low-K(1) DRV 140°C/W 20°C/W 715 mW High-K(2) DRV 75°C/W 20°C/W 1330 mW (1) (2) TA = 85°C POWER RATING TA = 110°C POWER RATING 155 mW 114 mW 42 mW 340 mW 250 mW 93 mW 7.1 mW/°C 395 mW 285 mW 107 mW 13.3 mW/°C 730 mW 530 mW 200 mW The JEDEC low-K (1s) board used to derive this data was a 3in × 3in, two-layer board with 2-ounce copper traces on top of the board. The JEDEC high-K (2s2p) board used to derive this data was a 3in × 3in, multilayer board with 1-ounce internal power and ground planes and 2-ounce copper traces on top and bottom of the board. 7.5 Electrical Characteristics over recommended operating junction temperature range, 2.5 V ≤ VIN ≤ 6.5 V, RILIM = 14.3 kΩ, V/EN = 0 V, or VEN = 5.0 V (unless otherwise noted) TEST CONDITIONS(1) PARAMETER MIN TYP MAX 94 100 UNIT POWER SWITCH DBV package, TJ = 25 °C DBV package, –40 °C ≤TJ ≤125 °C rDS(on) Static drain-source on-state resistance 140 DRV package, TJ = 25 °C 100 DRV package, –40 °C ≤TJ ≤105 °C tf Rise time, output Fall time, output 150 VIN = 6.5 V 1.0 1.5 VIN = 2.5 V 0.65 1.0 VIN = 6.5 V mΩ 145 DRV package, –40 °C ≤TJ ≤125 °C tr 115 CL = 1 μF, RL = 100 Ω, (see Figure 8-1) VIN = 2.5 V 0.2 0.5 0.2 0.5 ms ENABLE INPUT EN OR EN VIH High-level input voltage VIL Low-level input voltage IEN Input current ton Turnon time toff Turnoff time 1.1 0.66 VEN = 0 V or 6.5 V, V/EN = 0 V or 6.5 V –0.5 CL = 1 μF, RL = 100 Ω, (see Figure 8-1) V 0.5 μA 3 ms 3 ms CURRENT LIMIT IOS IOC 6 Short-circuit current, OUT connected to GND Current-limit threshold (Maximum DC output current IOUT delivered to load) Submit Document Feedback RILIM = 80.6 kΩ 160 265 350 RILIM = 38.3 kΩ 350 550 700 RILIM = 15 kΩ 1100 1450 1700 RILIM = 80.6 kΩ 340 365 390 RILIM = 38.3 kΩ 670 715 755 RILIM = 15 kΩ 1600 1700 1800 mA Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 7.5 Electrical Characteristics (continued) over recommended operating junction temperature range, 2.5 V ≤ VIN ≤ 6.5 V, RILIM = 14.3 kΩ, V/EN = 0 V, or VEN = 5.0 V (unless otherwise noted) TEST CONDITIONS(1) PARAMETER tIOS Response time to short circuit MIN VIN = 5.0 V (see Figure 8-2) TYP MAX UNIT 2 μs REVERSE-VOLTAGE PROTECTION Reverse-voltage comparator trip point (VOUT – VIN) Time from reverse-voltage condition to MOSFET turn off VIN = 5.0 V 95 135 190 mV 3 5 7 ms 0.1 1 μA SUPPLY CURRENT IIN_off Supply current, low-level output VIN = 6.5 V, No load on OUT, V EN = 6.5 V or VEN = 0 V, 14.3 kΩ ≤ RILIM ≤ 80.6 kΩ IIN_on Supply current, high-level output VIN = 6.5 V, No load on OUT, V EN = 0 V or VEN = 6.5 V RILIM = 15 kΩ 150 μA RILIM = 80.6 kΩ 130 μA IREV Reverse leakage current VOUT = 6.5 V, VIN = 0 V TJ = 25 °C 0.01 1 μA 2.45 UNDERVOLTAGE LOCKOUT VUVLO Low-level input voltage, IN VIN rising 2.35 Hysteresis, IN TJ = 25 °C 25 V mV FAULT FLAG VOL Output low voltage, FAULT I/FAULT = 1 mA 180 mV Off-state leakage V/FAULT = 6.5 V 1 μA FAULT deglitch FAULT assertion or de-assertion due to overcurrent condition 5 7.5 10 ms FAULT assertion or de-assertion due to reverse-voltage condition 2 4 6 ms THERMAL SHUTDOWN Thermal shutdown threshold 155 °C Thermal shutdown threshold in current-limit 135 °C Hysteresis (1) 15 °C Pulse-testing techniques maintain junction temperature close to ambient temperature; thermal effects must be taken into account separately. Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 7 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 7.6 Typical Characteristics 8 Figure 7-1. Turnon Delay and Rise Time Figure 7-2. Turnoff Delay and Fall Time Figure 7-3. Device Enabled into Short-Circuit Figure 7-4. Full-Load to Short-Circuit Transient Response Figure 7-5. Short-Circuit to Full-Load Recovery Response Figure 7-6. No-Load to Short-Circuit Transient Response Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 Figure 7-8. No Load to 1Ω Transient Response Figure 7-7. Short-Circuit to No-Load Recovery Response Figure 7-9. 1Ω to No Load Transient Response Figure 7-10. Reverse-Voltage Protection Response 2.40 UVLO - Undervoltage Lockout - V 2.39 2.38 2.37 UVLO Rising 2.36 2.35 2.34 UVLO Falling 2.33 2.32 2.31 Figure 7-11. Reverse-Voltage Protection Recovery 2.30 -50 0 50 100 150 TJ - Junction Temperature - °C Figure 7-12. UVLO – Undervoltage Lockout – V Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 9 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 150 0.45 VIN = 6.5 V 0.40 VIN = 5 V 0.35 VIN = 3.3 V RILIM = 20 kW 0.30 0.25 VIN = 2.5 V 0.20 0.15 0.10 0.05 0 50 TJ - Junction Temperature - °C 100 VIN = 5 V 105 VIN = 3.3 V 90 75 VIN = 2.5 V 60 45 30 0 -50 150 Figure 7-13. IIN – Supply Current, Output Disabled – μA 0 50 TJ - Junction Temperature - °C 100 150 Figure 7-14. IIN – Supply Current, Output Enabled – μA 150 rDS(on) - Static Drain-Source On-State Resistance - mW 20 VIN = 5 V, TA = 25°C 18 16 Current Limit Response - ms 120 15 0 -50 14 12 10 8 6 4 2 0 0 1.5 3 Peak Current - A 4.5 Figure 7-15. Current Limit Response – μs 10 VIN = 6.5 V 135 IIN - Supply Current, Output Enabled - mA IIN - Supply Current, Output Disabled - mA 0.50 6 125 DRV Package 100 DBV Package 75 50 25 0 -50 0 50 TJ - Junction Temperature - °C 100 150 Figure 7-16. MOSFET rDS(on) Vs. Junction Temperature Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 8 Parameter Measurement Information OUT tf tr RL CL 90% VOUT 10% 90% 10% TEST CIRCUIT 50% VEN VEN 50% toff ton VOUT 50% 50% toff ton 90% 90% VOUT 10% 10% VOLTAGE WAVEFORMS Figure 8-1. Test Circuit and Voltage Waveforms IOS IOUT tIOS Figure 8-2. Response Time to Short-Circuit Waveform VOUT DECREASING LOAD RESISTANCE DECREASING LOAD RESISTANCE IOS IOC IOUT Figure 8-3. Output Voltage vs. Current-Limit Threshold Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 11 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 9 Detailed Description 9.1 Overview The TPS2550/51 are current-limited, power distribution switches using N-channel MOSFETs for applications where short-circuits or heavy capacitive loads are encountered. These devices allow the user to program the current-limit threshold between 100 mA and 1.1 A via an external resistor. Additional device shutdown features include overtemperature protection and reverse-voltage protection. The device incorporates an internal charge pump and gate drive circuitry necessary to drive the N-channel MOSFET. The charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate of the MOSFET above the source. The charge pump operates from input voltages as low as 2.5 V and requires little supply current. The driver controls the gate voltage of the power switch. The driver incorporates circuitry that controls the rise and fall times of the output voltage to limit large current and voltage surges and provide built-in soft-start functionality. 9.2 Functional Block Diagram - Reverse Voltage Comparator + IN OUT CS 4-ms Deglitch Current Sense Charge Pump Driver EN Current Limit FAULT UVLO GND Thermal Sense 8-ms Deglitch ILIM 9.3 Feature Description 9.3.1 Overcurrent The TPS2550/51 responds to an overcurrent condition by limiting its output current to the IOC and IOS levels shown in Figure 9-1. Three response profiles are possible depending on the loading conditions and are summarized in Figure 8-3. One response profile occurs if the TPS2550/51 is enabled into a short-circuit. The output voltage is held near zero potential with respect to ground and the TPS2550/51 ramps the output current to IOS (see Figure 7-3). A second response profile occurs if a short is applied to the output after the TPS2550/51 is enabled. The device responds to the overcurrent condition within time tIOS (see Figure 8-2). The current-sense amplifier is over-driven during this time and momentarily disables the internal current-limit MOSFET. The current-sense amplifier gradually recovers and limits the output current to IOS. A third response profile occurs if the load current gradually increases. The device first limits the load current to IOC. If the load demands a current greater than IOC, the TPS2550/51 folds back the current to IOS and the output voltage decreases to IOS x RLOAD for a resistive load, which is shown in Figure 8-3. The TPS2550/51 thermal cycles if an overload condition is present long enough to activate thermal limiting in any of the above cases. The device turns off when the junction temperature exceeds 135°C (typ). The device remains off until the junction temperature cools 15°C (typ) and then restarts. The TPS2550/51 cycles on/off until the overload is removed (see Figure 7-5 and Figure 7-7) . 12 Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 9.3.2 Reverse-Voltage Protection The reverse-voltage protection feature turns off the N-channel MOSFET whenever the output voltage exceeds the input voltage by 135 mV (typical) for 4-ms. This feature prevents damage to devices on the input side of the TPS2550/51 by preventing significant current from sinking into the input capacitance. The N-channel MOSFET is allowed to turn-on once the output voltage goes below the input voltage for the same 4-ms deglitch time. The reverse-voltage comparator also asserts the FAULT output (active-low) after 4-ms. 9.3.3 FAULT Response The FAULT open-drain output is asserted (active low) during an overcurrent, overtemperature or reverse-voltage condition. The output remains asserted until the fault condition is removed. The TPS2550/51 is designed to eliminate false FAULT reporting by using an internal delay "deglitch" circuit for overcurrent (7.5-ms) and reversevoltage (4-ms) conditions without the need for external circuitry. This "deglitch" circuit ensures that FAULT is not accidentally asserted due to normal operation such as starting into a heavy capacitive load. The deglitch circuitry delays entering and leaving fault conditions. Overtemperature conditions are not deglitched and assert the FAULT signal immediately. 9.3.4 Undervoltage Lockout (UVLO) The undervoltage lockout (UVLO) circuit disables the power switch until the input voltage reaches the UVLO turn-on threshold. Built-in hysteresis prevents unwanted on/off cycling due to input voltage drop from large current surges. 9.3.5 ENABLE ( EN or EN) The logic enable controls the power switch, bias for the charge pump, driver, and other circuits to reduce the supply current. The supply current is reduced to less than 1-μA when a logic high is present on EN or when a logic low is present on EN. A logic low input on EN or a logic high input on EN enables the driver, control circuits, and power switch. The enable input is compatible with both TTL and CMOS logic levels. 9.3.6 Thermal Sense The TPS2550/51 protects itself with two independent thermal sensing circuits that monitor the operating temperature of the power-switch and disables operation if the temperature exceeds recommended operating conditions. The device operates in constant-current mode during an overcurrent conditions, which increases the voltage drop across power-switch. The power dissipation in the package is proportional to the voltage drop across the power-switch, so the junction temperature rises during an overcurrent condition. The first thermal sensor turns off the power-switch when the die temperature exceeds 135°C and the part is in current limit. The second thermal sensor turns off the power-switch when the die temperature exceeds 155°C regardless of whether the power-switch is in current limit. Hysteresis is built into both thermal sensors, and the switch turns on after the device has cooled approximately 15°C. The switch continues to cycle off and on until the fault is removed. The open-drain false reporting output FAULT is asserted (active low) immediately during an overtemperature shutdown condition. 9.3.7 Device Functional Modes There are no other functional modes. 9.4 Programming 9.4.1 Programming the Current-Limit Threshold The overcurrent threshold is user programmable via an external resistor. Many applications require that the minimum current-limit is above a certain current level or that the maximum current-limit is below a certain current level, so it is important to consider the tolerance of the overcurrent threshold when selecting a value for RILIM. The following equations and Figure 9-1 can be used to calculate the resulting overcurrent threshold for a given external resistor value ®ILIM). Figure 9-1 includes current-limit tolerance due to variations caused by temperature and process. To reduce parasitic effects on the current-limit accuracy, make the traces routing the RILIM resistor to the TPS2550/51 as short as possible. Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 13 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 There are two important current-limit thresholds for the device and are related by Figure 8-3. The first threshold is the short-circuit current threshold IOS. IOS is the current delivered to the load if the part is enabled into a short-circuit or a short-circuit is applied during normal operation. The second threshold is the overcurrent threshold IOC. IOC is the peak DC current that can be delivered to the load before the device begins to limit current. IOC is important if ramped loads or slow transients are common to the application. It is important to consider both IOS and IOC when choosing RILIM. RILIM can be selected to provide a current-limit threshold that occurs 1) above a minimum load current or 2) below a maximum load current. To design above a minimum current-limit threshold, find the intersection of RILIM and the maximum desired load current on the IOS(min) curve and choose a value of RILIM below this value. Programming the current-limit above a minimum threshold is important to ensure start-up into full-load or heavy capacitive loads. The resulting maximum DC load current is the intersection of the selected value of RILIM and the IOC(max) curve. To design below a maximum DC current level, find the intersection of RILIM and the maximum desired load current on the IOC(max) curve and choose a value of RILIM above this value. Programming the current-limit below a maximum threshold is important to avoid current-limiting upstream power supplies causing the input voltage bus to droop. The resulting minimum short-circuit current is the intersection of the selected value of RILIM and the IOS(min) curve. Overcurrent Threshold Equations (IOC): • • • IOC(max) (mA) = (24500 V) / (RILIM kΩ) 0.975 + 50 IOC(typ) (mA) = (23800 V) / (RILIM kΩ) 0.985 + 50 IOC(min) (mA) = (23100 V) / (RILIM kΩ) 0.996 + 50 Short-Circuit Current Equations (IOS): • • • IOS(max) (mA) = (25500 V) / (RILIM kΩ) 1.013 + 50 IOS(typ) (mA) = (28700 V) / (RILIM kΩ) 1.114 + 50 IOS(min) (mA) = (39700 V) / (RILIM kΩ) 1.342 + 50 where 14.3 kΩ ≤ RILIM ≤ 80.6 kΩ. IOS(typ) and IOS(max) are not plotted to improve graph clarity. 1800 Current-Limit Threshold - mA 1700 1600 1500 1400 IOC(max) 1300 1200 1100 1000 IOC(typ) IOC(min) 900 800 700 600 500 400 300 200 100 0 15 IOS(min) 20 25 30 35 40 45 50 RILIM - kW 55 60 65 70 75 80 Figure 9-1. Current-Limit Threshold Vs.RILIM 14 Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 10 Application and Implementation Note Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 10.1 Application Information The TPS255x current-limited power switch uses N-channel MOSFETs in applications requiring continuous load current. The device enters constant-current mode when the load exceeds the current limit threshold. 10.2 Typical Applications 10.2.1 Two-Level Current-Limit Circuit Some applications require different current-limit thresholds depending on external system conditions. Figure 10-1 shows an implementation for an externally controlled, two-level current-limit circuit. The current-limit threshold is set by the total resistance from ILIM to GND (see previously discussed "Programming the CurrentLimit Threshold" section). A logic-level input enables/disables MOSFET Q1 and changes the current-limit threshold by modifying the total resistance from ILIM to GND. Additional MOSFETs/resistor combinations can be used in parallel to Q1/R2 to increase the number of additional current-limit levels. Note Do not drive the ILIM directly with an external signal. Input TPS2550/51 0.1 mF IN Output OUT RFAULT 100 kW FAULT Signal FAULT Control Signal EN CLOAD R1 80.6 kW ILIM R2 20 kW GND Power Pad RLOAD Current Limit Control Signal Q1 2N7002 Figure 10-1. Two-Level Current-Limit Circuit 10.2.2 Design Requirements For this example, use the parameters shown in Table 10-1. Table 10-1. Design Requirements PARAMETER VALUE Input voltage 5V Output voltage 5V Above a minimum current limit 1000 mA Below a maximum current limit 1250 mA 10.2.3 Detail Design Procedures Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 15 TPS2550, TPS2551 SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 www.ti.com 10.2.3.1 Designing Above a Minimum Current Limit Some applications require that current-limiting cannot occur below a certain threshold. For this example, assume that 1 A must be delivered to the load so that the minimum desired current-limit threshold is 1000 mA. Use the IOS equations and Figure 9-1 to select RILIM. • IOS(min) (mA) = 1000 mA • IOS(min) (mA) = (39700 V) / (RILIM (kΩ)) 1.342 + 50 • RILIM (kΩ) = [(39700 V) / (IOS(min) (mA) - 50)]1/1.342 • RILIM = 16.14 kΩ Select the closest 1% resistor less than the calculated value: RILIM = 16 kΩ. This selection sets the minimum current-limit threshold at 1 A . Use the IOC equations, Figure 9-1, and the previously calculated value for RILIM to calculate the maximum resulting current-limit threshold. • RILIM = 16 kΩ • IOC(max) (mA) = (24500 V) / (RILIM (kΩ)) 0.975 + 50 • IOC(max) (mA) = (24500 V) / (16 (kΩ))0.975 + 50 • IOC(max) = 1691 mA The resulting maximum current-limit threshold is 1.69 A with a 16 kΩ resistor. 10.2.3.2 Designing Below a Maximum Current Limit Some applications require that current-limiting must occur below a certain threshold. For this example, assume that the desired upper current-limit threshold must be below 1.25 A to protect an up-stream power supply. Use the IOC equations and Figure 9-1 to select RILIM. • IOC(max) (mA) = 1250 mA • IOC(max) (mA) = (24500 V) / (RILIM (kΩ)) 0.975 + 50 • RILIM (kΩ) = [(24500 V) / (IOC(max) (mA) - 50)]1/0.975 • RILIM = 22.05 kΩ Select the closest 1% resistor greater than the calculated value: RILIM = 22 kΩ. This selection sets the maximum current-limit threshold at 1.25 A . Use the IOS equations, Figure 9-1, and the previously calculated value for RILIM to calculate the minimum resulting current-limit threshold. • RILIM = 22 kΩ • IOS(min) (mA) = (39700 V) / (RILIM (kΩ)) 1.342 + 50 • IOS(min) (mA) = (39700 V) / (22 (kΩ)) 1.342 + 50 • IOS(min) = 677 mA The resulting minimum current-limit threshold is 677 mA with a 22 kΩ resistor. 10.2.3.3 Input and Output Capacitance Input and output capacitance improve the performance of the device; make sure to optimize the actual capacitance for the particular application. For all applications, a 0.01 μF to 0.1μF ceramic bypass capacitor between IN and GND is recommended as close to the device as possible for local noise de-coupling. This precaution reduces ringing on the input due to power-supply transients. Additional input capacitance may be needed on the input to reduce voltage overshoot from exceeding the absolute maximum voltage of the device during heavy transients, which is especially important during bench testing when long, inductive cables are used to connect the evaluation board to the bench power-supply. Placing a high-value electrolytic capacitor on the output pin is recommended when the large transient currents are expected on the output. Additionally, bypassing the output with a 0.01 μF to 0.1 μF ceramic capacitor improves the immunity of the device to short-circuit transients. 10.2.4 Auto-Retry Functionality Some applications require that an overcurrent condition disables the part momentarily during a fault condition and re-enables after a pre-set time. This auto-retry functionality can be implemented with an external resistor and capacitor. During a fault condition, FAULT pulls low disabling the part. The part is disabled when EN is pulled low, and FAULT goes high impedance allowing CRETRY to begin charging. The part re-enables when the 16 Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 voltage on EN reaches the turnon threshold, and the auto-retry time is determined by the resistor/capacitor time constant. The part continues to cycle in this manner until the fault condition is removed. TPS2551 0.1 mF Input Output IN OUT RLOAD RFAULT 100 kW CLOAD ILIM FAULT 1 kW RILIM GND EN CRETRY 20 kW Power Pad 0.1 mF Figure 10-2. Auto-Retry Functionality Some applications require auto-retry functionality and the ability to enable/disable with an external logic signal. The figure below shows how an external logic signal can drive EN through RFAULT and maintain auto-retry functionality. The resistor/capacitor time constant determines the auto-retry time-out period. TPS2551 Input IN Output OUT RLOAD 0.1 mF External Logic Signal & Driver CLOAD RFAULT 100 kW CRETRY FAULT 1kW EN ILIM RILIM GND 20 kW Power Pad 0.1 mF Figure 10-3. Auto-Retry Functionality With External EN Signal 10.2.5 Latch-Off Functionality The circuit in Figure 10-4 uses an SN74HC00 quad-NAND gate to implement overcurrent latch-off. The SN74HC00 high-speed CMOS logic gate is selected because it operates over the 2.5V – 6.5V range of the TPS2550/51. This circuit is designed to work with the active-high TPS2551. ENABLE must be logic low during start-up until VIN is stable to ensure that the switch initializes in the OFF state. A logic high on ENABLE turns on the switch after VIN is stable. FAULT momentarily pulls low during an overcurrent condition, which latches STAT logic low and disables the switch. The host can monitor STAT for an overcurrent condition. Toggling ENABLE resets STAT and re-enables the switch. Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 17 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 TPS2551 0.1 mF Input Output IN 0.1 mF OUT RLOAD 10 kW CLOAD External Logic Enable Signal ILIM EN 15 kW GND FAULT RFAULT 10 kW Power Pad SN74HC00D STAT Figure 10-4. Overcurrent Latch-Off Using a Quad-NAND Gate 10.2.6 Typical Application as USB Power Switch TPS2550/51 5 V USB USB Data 0.1 mF INPUT USB Port OUT IN RFAULT 100 kW 120 mF * FAULT Signal FAULT ILIM Control Signal EN GND RILIM 15 kW PowerPAD * USB Requirement that downstream-facing ports are bypassed with at least 120 mF per hub Figure 10-5. Typical Application as USB Power Switch 10.2.6.1 Design Requirements For this example, use the parameters shown in Table 10-2. Table 10-2. Design Requirements PARAMETER VALUE Input voltage 5V Output voltage 5V Current 1250 mA 10.2.6.1.1 USB Power-Distribution Requirements USB can be implemented in several ways regardless of the type of USB device being developed. Several power-distribution features must be implemented. • • • 18 SPHs must: – Current-limit downstream ports – Report overcurrent conditions BPHs must: – Enable/disable power to downstream ports – Power up at <100 mA – Limit inrush current (<44 Ω and 10 μF) Functions must: – Limit inrush currents Submit Document Feedback Copyright © 2023 Texas Instruments Incorporated Product Folder Links: TPS2550 TPS2551 TPS2550, TPS2551 www.ti.com SLVS736C – FEBRUARY 2008 – REVISED OCTOBER 2023 – Power up at <100 mA The feature set of the TPS2550/51 meets each of these requirements. The integrated current-limiting and overcurrent reporting is required by self-powered hubs. The logic-level enable and controlled rise times meet the need of both input and output ports on bus-powered hubs and the input ports for bus-powered functions. 10.2.6.2 Detail Design Procedures 10.2.6.2.1 Universal Serial Bus (USB) Power-Distribution Requirements One application for this device is for current-limiting in universal serial bus (USB) applications. The original USB interface was a 12-Mb/s or 1.5-Mb/s, multiplexed serial bus designed for low-to-medium bandwidth PC peripherals (for example keyboards, printers, scanners, and mice). As the demand for more bandwidth increased, the USB 2.0 standard was introduced increasing the maximum data rate to 480-Mb/s. The four-wire USB interface is conceived for dynamic attach-detach (hot plug-unplug) of peripherals. Two lines are provided for differential data, and two lines are provided for 5-V power distribution. USB data is a 3.3-V level signal, but power is distributed at 5 V to allow for voltage drops in cases where power is distributed through more than one hub across long cables. Each function must provide its own regulated 3.3 V from the 5-V input or its own internal power supply. The USB specification classifies two different classes of devices depending on its maximum current draw. A device classified as low-power can draw up to 100 mA as defined by the standard. A device classified as high-power can draw up to 500 mA. It is important that the minimum current-limit threshold of the current-limiting power-switch exceed the maximum current-limit draw of the intended application. Always reference the latest USB standard when considering the current-limit threshold The USB specification defines two types of devices as hubs and functions. A USB hub is a device that contains multiple ports for different USB devices to connect and can be self-powered (SPH) or bus-powered (BPH). A function is a USB device that is able to transmit or