TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 DUAL CHANNEL PRECISION ADJUSTABLE CURRENT-LIMITED POWER SWITCHES Check for Samples: TPS2560 TPS2561 FEATURES 1 • • • • • • • • • • • • 2 Two separate current limiting channels Meets USB Current-Limiting Requirements Adjustable Current Limit, 250 mA–2.8 A (typ) +/- 7.5% Current-Limit Accuracy at 2.8A Fast Overcurrent Response - 3.5-μS (typ) Two 44-mΩ High-Side MOSFETs Operating Range: 2.5 V to 6.5 V 2-μA Maximum Standby Supply Current Built-in Soft-Start 15 kV / 8 kV System-Level ESD Capable UL Listed – File No. E169910 CB & Nemko Certified APPLICATIONS • • • • DESCRIPTION The TPS2560 and TPS2561 are dual-channel power-distribution switches intended for applications where precision current limiting is required or heavy capacitive loads and short circuits are encountered. These devices offer a programmable current-limit threshold between 250 mA and 2.8 A (typ) per channel via an external resistor. The power-switch rise and fall times are controlled to minimize current surges during turn on/off. Each channel of the TPS2560/61 devices limit the output current to a safe level by switching into a constant-current mode when the output load exceeds the current-limit threshold. The FAULTx logic output for each channel independently asserts low during overcurrent and over temperature conditions. USB Ports/Hubs Digital TV Set-Top Boxes VOIP Phones TPS2560/61 DRC PACKAGE (TOP VIEW) GND IN IN EN1 EN2 1 2 3 4 5 PAD 10 9 8 7 6 TPS2560/61 2.5V – 6.5V FAULT1 OUT1 OUT2 ILIM FAULT2 ENx = Active Low for the TPS2560 ENx = Active High for the TPS2561 2x RFAULT 100 kΩ Fault Signal Fault Signal Control Signal Control Signal 0.1 μF IN IN VOUT1 OUT1 OUT2 ILIM FAULT1 FAULT2 GND EN1 EN2 Power Pad VOUT2 RILIM 2x CLOAD Figure 1. Typical Application as USB Power Switch 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PowerPAD is a trademark of Texas Instruments. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2009, Texas Instruments Incorporated TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. AVAILABLE OPTIONS AND ORDERING INFORMATION DEVICE (1) TPS2560 TPS2561 (1) (2) (3) AMBIENT TEMPERATURE SON (3) (DRC) MARKING ENABLE Active low TPS2560DRC 2560 Active high TPS2561DRC 2561 (2) –40°C to 85°C RECOMMENDED MAXIMUM CONTINUOUS LOAD CURRENT PER CHANNEL 2.5 A For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com. 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. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range unless otherwise noted (1) (2) Voltage range on IN, OUTx, ENx or ENx, ILIM, FAULTx Voltage range from IN to OUTx Continuous output current ILIM source current HBM CDM ESD – system level (contact/air) (3) (1) (2) (3) (4) –0.3 to 7 V –7 to 7 V See the Dissipation Rating Table Continuous FAULTx sink current TJ UNIT Internally Limited Continuous total power dissipation ESD VALUE Maximum junction temperature 25 mA Internally Limited mA 2 kV 500 V 8/15 kV –40 to OTSD2 (4) °C Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. Voltages are referenced to GND unless otherwise noted. Surges per EN61000-4-2, 1999 applied between USB and output ground of the TPS2560EVM (HPA424) evaluation module (documentation available on the Web.) These were the test level, no the failure threshold. Ambient over temperature shutdown threshold DISSIPATION RATING TABLE BOARD PACKAGE THERMAL RESISTANCE (1) θJA THERMAL RESISTANCE θJC TA ≤ 25°C POWER RATING High-K (2) DRC 41.6 °C/W 10.7 °C/W 2403 mW (1) (2) 2 Mounting per the PowerPADTM Thermally Enhanced Package application report (SLMA002) 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. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 RECOMMENDED OPERATING CONDITIONS VIN MIN MAX 2.5 6.5 TPS2560 0 6.5 TPS2561 0 6.5 Input voltage, IN VENx V/ENx Enable voltage UNIT V V VIH High-level input voltage on ENx or ENx VIL Low-level input voltage on ENx or ENx IOUTx Continuous output current per channel, OUTx 0 2.5 A Continuous FAULTx sink current 0 10 mA –40 125 °C 20 187 kΩ TJ Operating virtual junction temperature RILIM Recommended resistor limit range 1.1 V 0.66 ELECTRICAL CHARACTERISTICS over recommended operating conditions, V/ENx = 0 V, or VENx = VIN (unless otherwise noted) TEST CONDITIONS (1) PARAMETER MIN TYP MAX 44 50 UNIT POWER SWITCH rDS(on) Static drain-source on-state resistance per channel, IN to OUTx tr Rise time, output tf Fall time, output TJ = 25 °C –40 °C ≤TJ ≤125 °C 70 VIN = 6.5 V 2 3 VIN = 2.5 V 1 2 3 0.6 0.8 1.0 0.4 0.6 0.8 VIN = 6.5 V CLx = 1 μF, RLx = 100 Ω, (see Figure 2) VIN = 2.5 V mΩ 4 ms ENABLE INPUT EN OR EN Enable pin turn on/off threshold 0.66 IEN Input current ton Turnon time toff Turnoff time 1.1 55 (2) Hysteresis VENx = 0 V or 6.5 V, V/ENx = 0 V or 6.5 V –0.5 CLx = 1 μF, RLx = 100 Ω, (see Figure 2) V mV 0.5 μA 9 ms 6 ms CURRENT LIMIT IOS tIOS (1) (2) Current-limit threshold per channel (Maximum DC output current IOUTx delivered to load) & Short-circuit current, OUTx connected to GND Response time to short circuit RILIM = 20 kΩ 2590 2800 3005 RILIM = 61.9 kΩ 800 900 1005 RILIM = 100 kΩ 470 560 645 VIN = 5.0 V (see Figure 3) 3.5 (2) mA μs Pulse-testing techniques maintain junction temperature close to ambient temperature; thermal effects must be taken into account separately. These parameters are provided for reference only, and do not constitute part of TI's published specifications for purposes of TI's product warranty. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 3 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com ELECTRICAL CHARACTERISTICS (continued) over recommended operating conditions, V/ENx = 0 V, or VENx = VIN (unless otherwise noted) TEST CONDITIONS (1) PARAMETER MIN TYP MAX UNIT SUPPLY CURRENT IIN_off Supply current, low-level output 0.1 2.0 μA RILIM = 20 kΩ 100 125 μA RILIM = 100 kΩ 85 110 μA 0.01 1.0 μA 2.35 2.45 VIN = 6.5 V, No load on OUTx, V ENx = 6.5 V or VENx = 0 V IIN_on Supply current, high-level output VIN = 6.5 V, No load on OUT IREV Reverse leakage current VOUTx = 6.5 V, VIN = 0 V TJ = 25°C UNDERVOLTAGE LOCKOUT UVLO Low-level input voltage, IN VIN rising Hysteresis, IN TJ = 25°C 35 V mV FAULTx FLAG VOL Output low voltage, FAULTx I FAULTx = 1 mA 180 Off-state leakage V FAULTx = 6.5 V FAULTx deglitch FAULTx assertion or de-assertion due to overcurrent condition 6 9 mV 1 μA 13 ms THERMAL SHUTDOWN OTSD2 Thermal shutdown threshold 155 OTSD Thermal shutdown threshold in current-limit 135 Hysteresis (3) 4 °C °C 20 (3) °C These parameters are provided for reference only, and do not constitute part of TI's published specifications for purposes of TI's product warranty. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 DEVICE INFORMATION Pin Functions PIN NAME I/O DESCRIPTION TPS2560 TPS2561 4 - I Enable input, logic low turns on channel one power switch - 4 I Enable input, logic high turns on channel one power switch 5 - I Enable input, logic low turns on channel two power switch EN2 - 5 I Enable input, logic high turns on channel two power switch GND 1 1 IN 2, 3 2, 3 I Input voltage; connect a 0.1 μF or greater ceramic capacitor from IN to GND as close to the IC as possible. FAULT1 10 10 O Active-low open-drain output, asserted during overcurrent or overtemperature condition on channel one. FAULT2 6 6 O Active-low open-drain output, asserted during overcurrent or overtemperature condition on channel two OUT1 9 9 O Power-switch output for channel one OUT2 8 8 O Power-switch output for channel two ILIM 7 7 O External resistor used to set current-limit threshold; recommended 20 kΩ ≤ RILIM ≤ 187 kΩ. PAD PAD EN1 EN1 EN2 PowerPAD ™ Ground connection; connect externally to PowerPAD Internally connected to GND; used to heat-sink the part to the circuit board traces. Connect PowerPAD to GND pin externally. FUNCTIONAL BLOCK DIAGRAM Current Sense CS IN OUT1 FAULT1 9-ms Deglitch Thermal Sense Charge Pump EN1 EN2 Current Limit Driver UVLO ILIM FAULT2 Thermal Sense 9-ms Deglitch GND CS OUT2 Current Sense Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 5 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com PARAMETER MEASUREMENT INFORMATION OUTx tr CLx RLx VOUTx tf 90% 90% 10% 10% TEST CIRCUIT VENx 50% 50% VENx ton toff 50% 50% toff ton 90% 90% VOUTx VOUTx 10% 10% VOLTAGE WAVEFORMS Figure 2. Test Circuit and Voltage Waveforms IOS IOUTx tIOS Figure 3. Response Time to Short Circuit Waveform Decreasing Load Resistance VOUTx Decreasing Load Resistance IOUTx IOS Figure 4. Output Voltage vs. Current-Limit Threshold 6 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 TYPICAL CHARACTERISTICS TPS2560/61 VIN = 5V 0.1 uF 2x RFAULT 100 kΩ IN IN ILIM FAULT 1 FAULT 2 GND EN1 EN2 Power Pad Faultx Signals Control Signals VOUT1 OUT1 OUT2 VOUT2 24.9kΩ 2x 150 µF Figure 5. Typical Characteristics Reference Schematic VOUT1 5 V/div VOUT1 5 V/div VOUT2 5 V/div VOUT2 5 V/div VEN1_bar 5 V/div VEN1_bar VEN1_bar = VEN2_bar 5 V/div VEN1_bar = VEN2_bar IIN 2 A/div IIN 2 A/div t - Time - 2 ms/div t - Time - 2 ms/div Figure 6. Turn-on Delay and Rise Time VOUT1 5 V/div Figure 7. Turn-off Delay and Fall Time VOUT1 5 V/div VOUT2 5 V/div VOUT2 5 V/div FAULT2_bar 5 V/div FAULT2_bar 5 V/div IIN 2 A/div IIN 2 A/div t - Time - 20 ms/div t - Time - 20 ms/div Figure 8. Full-Load to Short-Circuit Transient Response Figure 9. Short-Circuit to Full-Load Recovery Response Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 7 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com TYPICAL CHARACTERISTICS (continued) 700 2.335 IIN - Supply Current, Output Disabled - nA UVLO - Undervoltage Lockout - V 2.33 2.325 UVLO Rising 2.32 2.315 2.31 2.305 UVLO Falling 2.3 600 500 400 VIN = 6.5 V 300 200 VIN = 2.5 V 100 0 2.295 2.29 -50 0 50 TJ - Junction Temperature - °C 100 -100 -50 150 Figure 10. UVLO – Undervoltage Lockout – V 150 80 VIN = 3.3 V VIN = 2.5 V 60 40 RILIM = 20 kΩ 20 0 -50 0 RILIM = 20kΩ TJ = 125°C 100 IIN Supply Current vs. VIN Enabled - μA IIN - Supply Current, Output Enabled - mA 100 120 VIN = 6.5 V VIN = 5 V 50 TJ - Junction Temperature - °C 100 110 100 90 80 TJ = 25°C TJ = -40°C 70 60 150 2 Figure 12. IIN – Supply Current, Output Enabled – µA 3 4 5 Input Voltage - V 6 7 Figure 13. IIN – Supply Current, Output Enabled – µA 70 0.6 60 0.5 IDS - Static Drain-Source Current - A rDS(on) - Static Drain-Source On-State Resistance - mW 50 TJ - Junction Temperature - °C Figure 11. IIN – Supply Current, Output Disabled – nA 120 50 40 30 20 TA = -40°C 0.4 TA = 25°C TA = 125°C 0.3 0.2 RILIM = 100 kW 0.1 10 0 -50 0 0 0 50 TJ - Junction Temperature - °C 100 Figure 14. MOSFET rDS(on) Vs. Junction Temperature 8 0 150 50 100 VIN - VOUT - mV/div 150 200 Figure 15. Switch Current Vs. Drain-Source Voltage Across Switch Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 TYPICAL CHARACTERISTICS (continued) 3.0 1.0 2.5 0.8 0.7 IDS - Static Drain-Source Current - A IDS - Static Drain-Source Current - A 0.9 TA = -40°C 0.6 TA = 25°C 0.5 TA = 125°C 0.4 0.3 RILIM = 61.9 kW 0.2 TJ = -40°C 2.0 TJ = 25°C 1.5 1.0 TJ = 125°C RILIM = 20kΩ 0.5 0.1 0 0 0 20 40 60 80 100 VIN - VOUT - mV/div 120 140 160 Figure 16. Switch Current Vs. Drain-Source Voltage Across Switch 0 50 100 VIN-VOUT - mV 150 200 Figure 17. Switch Current vs. Drain-Source Voltage Across Switch Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 9 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com DETAILED DESCRIPTION OVERVIEW The TPS2560/61 is a dual-channel, current-limited power-distribution switch using N-channel MOSFETs for applications where short circuits or heavy capacitive loads will be encountered. This device allows the user to program the current-limit threshold between 250 mA and 2.8 A (typ) per channel via an external resistor. This device incorporates an internal charge pump and gate drive circuitry necessary to drive the N-channel MOSFETs. The charge pump supplies power to the driver circuit for each channel 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 provides built-in soft-start functionality. Each channel of the TPS2560/61 limits the output current to the programmed current-limit threshold IOS during an overcurrent or short-circuit event by reducing the charge pump voltage driving the N-channel MOSFET and operating it in the linear range of operation. The result of limiting the output current to IOS reduces the output voltage at OUTx because the N-channel MOSFET is no longer fully enhanced. OVERCURRENT CONDITIONS The TPS2560/61 responds to overcurrent conditions by limiting the output current per channel to IOS. When an overcurrent condition is detected, the device maintains a constant output current and reduces the output voltage accordingly. Two possible overload conditions can occur. The first condition is when a short circuit or partial short circuit is present when the device is powered-up or enabled. The output voltage is held near zero potential with respect to ground and the TPS2560/61 ramps the output current to IOS. The TPS2560/61 devices will limit the current to IOS until the overload condition is removed or the device begins to thermal cycle. The second condition is when a short circuit, partial short circuit, or transient overload occurs while the device is enabled and powered on. The device responds to the overcurrent condition within time tIOS (see Figure 3). The current-sense amplifier is overdriven during this time and momentarily disables the internal current-limit MOSFET. The current-sense amplifier recovers and ramps the output current to IOS. Similar to the previous case, the TPS2560/61 will limit the current to IOS until the overload condition is removed or the device begins to thermal cycle. The TPS2560/61 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 (min) while in current limit. The device remains off until the junction temperature cools 20°C (typ) and then restarts. The TPS2560/61 cycles on/off until the overload is removed (see Figure 9) . 10 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 FAULTx RESPONSE The FAULTx open-drain outputs are asserted (active low) on an individual channel during an overcurrent or overtemperature condition. The TPS2560/61 asserts the FAULTx signal until the fault condition is removed and the device resumes normal operation on that channel. The TPS2560/61 is designed to eliminate false FAULTx reporting by using an internal delay "deglitch" circuit (9-ms typ) for overcurrent conditions without the need for external circuitry. This ensures that FAULTx is not accidentally asserted due to normal operation such as starting into a heavy capacitive load. The deglitch circuitry delays entering and leaving current-limited induced fault conditions. The FAULTx signal is not deglitched when the MOSFET is disabled due to an overtemperature condition but is deglitched after the device has cooled and begins to turn on. This unidrectional deglitch prevents FAULTx oscillation during an overtemperature event. 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 droop during turn on. ENABLE (ENx OR ENx) The logic enables control the power switches and device supply current. The supply current is reduced to less than 2-μA when a logic high is present on ENx or when a logic low is present on ENx. A logic low input on ENx or a logic high input on ENx enables the driver, control circuits, and power switches. The enable inputs are compatible with both TTL and CMOS logic levels. THERMAL SENSE The TPS2560/61 self protects by using two independent thermal sensing circuits that monitor the operating temperature of the power switch and disable operation if the temperature exceeds recommended operating conditions. Each channel of the TPS2560/61 operates in constant-current mode during an overcurrent conditions, which increases the voltage drop across the power switch. The power dissipation in the package is proportional to the voltage drop across the power switch, which increases the junction temperature during an overcurrent condition. The first thermal sensor (OTSD) turns off the individual power switch channel when the die temperature exceeds 135°C (min) and the channel is in current limit. Hysteresis is built into the thermal sensor, and the switch turns on after the device has cooled approximately 20°C. The TPS2560/61 also has a second ambient thermal sensor (OTSD2). The ambient thermal sensor turns off both power switch channels when the die temperature exceeds 155°C (min) regardless of whether the power switch channels are in current limit and will turn on the power switches after the device has cooled approximately 20°C. The TPS2560/61 continues to cycle off and on until the fault is removed. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 11 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com APPLICATION INFORMATION INPUT AND OUTPUT CAPACITANCE Input and output capacitance improves the performance of the device; the actual capacitance should be optimized for the particular application. For all applications, a 0.1μF or greater ceramic bypass capacitor between IN and GND is recommended as close to the device as possible for local noise decoupling. 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 transient conditions. This is especially important during bench testing when long, inductive cables are used to connect the evaluation board to the bench power supply. Output capacitance is not required, but placing a high-value electrolytic capacitor on the output pin is recommended when large transient currents are expected on the output. PROGRAMMING THE CURRENT-LIMIT THRESHOLD The overcurrent threshold is user programmable via an external resistor, RILIM. RILIM sets the current-limit threshold for both channels. The TPS2560/61 use an internal regulation loop to provide a regulated voltage on the ILIM pin. The current-limit threshold is proportional to the current sourced out of ILIM. The recommended 1% resistor range for RILIM is 20 kΩ ≤ RILIM ≤ 187 kΩ to ensure stability of the internal regulation loop. 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 calculates the resulting overcurrent threshold for a given external resistor value (RILIM). The traces routing the RILIM resistor to the TPS2560/61 should be as short as possible to reduce parasitic effects on the current-limit accuracy. IOSmax (mA) = 52850V RILIM0.957kW IOSnom (mA) = 56000V RILIMkW IOSmin (mA) = 61200V RILIM1.056kW (1) 3000 2750 Current-Limit Threshold (mA) 2500 2250 2000 1750 1500 1250 1000 IOS(max) IOS(typ) 750 500 IOS(min) 250 0 20 30 40 50 60 70 80 90 100 110 120 130 140 150 RILIM – Current Limit Resistor – kΩ Figure 18. Current-Limit Threshold vs. RILIM 12 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 APPLICATION 1: DESIGNING ABOVE A MINIMUM CURRENT LIMIT Some applications require that current limiting cannot occur below a certain threshold. For this example, assume that 2 A must be delivered to the load so that the minimum desired current-limit threshold is 2000 mA. Use the IOS equations and Figure 18 to select RILIM. IOSmin (mA) = 2000mA IOSmin (mA) = 61200V RILIM1.056kW 1 æ 61200V ö÷1.056 ÷ RILIM (kW) = ççç çèIOSminmA ø÷÷ RILIM (kW) = 25.52kW (2) Select the closest 1% resistor less than the calculated value: RILIM = 25.5 kΩ. This sets the minimum current-limit threshold at 2 A . Use the IOS equations, Figure 18, and the previously calculated value for RILIM to calculate the maximum resulting current-limit threshold. RILIM (kW) = 25.5kW IOSmax (mA) = IOSmax (mA) = 52850V RILIM0.957kW 52850V 25.50.957kW IOSmax (mA) = 2382mA (3) The resulting maximum current-limit threshold is 2382 mA with a 25.5 kΩ resistor. APPLICATION 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 1000 mA to protect an up-stream power supply. Use the IOS equations and Figure 18 to select RILIM. IOSmax (mA) = 1000mA IOSmax (mA) = 52850V RILIM0.957kW 1 æ 52850V ÷ö0.957 ÷ RILIM (kW) = ççç çèIOSmax mA ÷÷ø RILIM (kW) = 63.16kW (4) Select the closest 1% resistor greater than the calculated value: RILIM = 63.4 kΩ. This sets the maximum current-limit threshold at 1000 mA . Use the IOS equations, Figure 18, and the previously calculated value for RILIM to calculate the minimum resulting current-limit threshold. RILIM (kW) = 63.4kW IOSmin (mA) = IOSmin (mA) = 61200V RILIM1.056kW 61200V 63.41.056 kW IOSmin (mA) = 765mA (5) The resulting minimum current-limit threshold is 765 mA with a 63.4 kΩ resistor. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 13 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com ACCOUNTING FOR RESISTOR TOLERANCE The previous sections described the selection of RILIM given certain application requirements and the importance of understanding the current-limit threshold tolerance. The analysis focused only on the TPS2560/61 performance and assumed an exact resistor value. However, resistors sold in quantity are not exact and are bounded by an upper and lower tolerance centered around a nominal resistance. The additional RILIM resistance tolerance directly affects the current-limit threshold accuracy at a system level. The following table shows a process that accounts for worst-case resistor tolerance assuming 1% resistor values. Step one follows the selection process outlined in the application examples above. Step two determines the upper and lower resistance bounds of the selected resistor. Step three uses the upper and lower resistor bounds in the IOS equations to calculate the threshold limits. It is important to use tighter tolerance resistors, e.g. 0.5% or 0.1%, when precision current limiting is desired. Table 1. Common RILIM Resistor Selections Resistor Tolerance Desired Nominal Current Limit (mA) Ideal Resistor (kΩ) Closest 1% Resistor (kΩ) 1% low (kΩ) 300 186.7 187 400 140.0 140 600 93.3 14 Actual Limits 1% high (kΩ) IOS MIN (mA) IOS Nom (mA) IOS MAX (mA) 185.1 188.9 241.6 299.5 357.3 138.6 141.4 328.0 400.0 471.4 93.1 92.2 94.0 504.6 601.5 696.5 800 70.0 69.8 69.1 70.5 684.0 802.3 917.6 1000 56.0 56.2 55.6 56.8 859.9 996.4 1129.1 1200 46.7 46.4 45.9 46.9 1052.8 1206.9 1356.3 1400 40.0 40.2 39.8 40.6 1225.0 1393.0 1555.9 1600 35.0 34.8 34.5 35.1 1426.5 1609.2 1786.2 1800 31.1 30.9 30.6 31.2 1617.3 1812.3 2001.4 2000 28.0 28 27.7 28.3 1794.7 2000.0 2199.3 2200 25.5 25.5 25.2 25.8 1981.0 2196.1 2405.3 2400 23.3 23.2 23.0 23.4 2188.9 2413.8 2633.0 2600 21.5 21.5 21.3 21.7 2372.1 2604.7 2831.9 2800 20.0 20 19.8 20.2 2560.4 2800.0 3034.8 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 POWER DISSIPATION AND JUNCTION TEMPERATURE The low on-resistance of the N-channel MOSFET allows small surface-mount packages to pass large currents. It is good design practice to estimate power dissipation and junction temperature. The below analysis gives an approximation for calculating junction temperature based on the power dissipation in the package. However, it is important to note that thermal analysis is strongly dependent on additional system level factors. Such factors include air flow, board layout, copper thickness and surface area, and proximity to other devices dissipating power. Good thermal design practice must include all system level factors in addition to individual component analysis. Begin by determining the rDS(on) of the N-channel MOSFET relative to the input voltage and operating temperature. As an initial estimate, use the highest operating ambient temperature of interest and read rDS(on) from the typical characteristics graph. Using this value, the power dissipation can be calculated by: PD = (RDS(on) × IOUT1 2) +(RDS(on) × IOUT2 2) Where: PD = Total power dissipation (W) rDS(on) = Power switch on-resistance of one channel (Ω) IOUTx = Maximum current-limit threshold set by RILIM(A) This step calculates the total power dissipation of the N-channel MOSFET. Finally, calculate the junction temperature: TJ = PD × θJA + TA Where: TA = Ambient temperature (°C) θJA = Thermal resistance (°C/W) PD = Total power dissipation (W) Compare the calculated junction temperature with the initial estimate. If they are not within a few degrees, repeat the calculation using the "refined" rDS(on) from the previous calculation as the new estimate. Two or three iterations are generally sufficient to achieve the desired result. The final junction temperature is highly dependent on thermal resistance θJA, and thermal resistance is highly dependent on the individual package and board layout. The Dissipating Rating Table provides example thermal resistances for specific packages and board layouts. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 15 TPS2560 TPS2561 SLVS930 – DECEMBER 2009 www.ti.com 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, FAULTx pulls ENx low disabling the part. The part is disabled when ENx is pulled below the turn-off threshold, and FAULTx goes high impedance allowing CRETRY to begin charging. The part re-enables when the voltage on ENx reaches the turn-on threshold, and the auto-retry time is determined by the resistor/capacitor time constant. The part will continue to cycle in this manner until the fault condition is removed. TPS2561 Input 0.1 μF OUT1 OUT2 IN RFAULT 2x 100 kΩ 2x CLOAD ILIM FAULT1 GND EN1 FAULT2 EN2 CRETRY 2x 0.22 µF VOUT1 VOUT2 RILIM 20 kΩ Power Pad Figure 19. 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. TPS2561 Input External Logic Signal & Drivers RFAULT 2x 100 kΩ CRETRY 2x 0.22 µF 0.1 μF IN OUT1 OUT2 VOUT1 VOUT2 2x CLOAD ILIM FAULT1 GND EN1 FAULT2 EN2 RILIM 20 kΩ Power Pad Figure 20. Auto-Retry Functionality With External EN Signal 16 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 TPS2560 TPS2561 www.ti.com SLVS930 – DECEMBER 2009 TWO-LEVEL CURRENT-LIMIT CIRCUIT Some applications require different current-limit thresholds depending on external system conditions. Figure 21 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 Current-Limit 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 MOSFET/resistor combinations can be used in parallel to Q1/R2 to increase the number of additional current-limit levels. NOTE ILIM should never be driven directly with an external signal. TPS2560/61 2.5V – 6.5V 2x RFAULT 100 kΩ Fault Signal Fault Signal Control Signal Control Signal 0.1 μF IN IN VOUT1 OUT1 OUT2 FAULT1 FAULT2 ILIM EN1 GND EN2 Power Pad VOUT2 2x CLOAD R1 187 kΩ R2 22.1 kΩ Q1 Current Limit Control Signal Figure 21. Two-Level Current-Limit Circuit Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS2560 TPS2561 17 PACKAGE OPTION ADDENDUM www.ti.com 10-Feb-2010 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS2560DRCR ACTIVE SON DRC 10 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS2560DRCT ACTIVE SON DRC 10 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS2561DRCR ACTIVE SON DRC 10 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS2561DRCT ACTIVE SON DRC 10 250 CU NIPDAU Level-2-260C-1 YEAR Green (RoHS & no Sb/Br) Lead/Ball Finish MSL Peak Temp (3) (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. 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