19-1450; Rev 0; 7/99 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown ____________________________Features ♦ +2.7V to +5.5V Input Range ♦ Programmable Current Limit 0.2A to 1.2A Range ±20% Accuracy ♦ 1.2A Continuous Load Current ♦ 1.8A Short-Circuit Current ♦ Low Quiescent Current 13µA at VIN = 3.3V 0.1µA with Switch Off ♦ Thermal Shutdown ♦ FAULT Indicator Output ♦ 0.07Ω On-Resistance ________________________Applications USB Ports USB Hubs Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX893LESA -40°C to +85°C 8 SO PCMCIA Slots Access Bus Slots Portable Equipment Typical Operating Circuit Pin Configuration TOP VIEW INPUT IN OUT OUTPUT 0.1µF* IN MAX893L OUT 8 FAULT IN 1 100k 1µF FAULT ON GND SET ON/OFF IN 2 MAX893L 7 OUT ON 3 6 OUT GND 4 5 SET RSET SO *USB SPECIFICATIONS REQUIRE HIGHER CAPACITANCE. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX893L General Description The MAX893L smart, low-voltage, P-channel, MOSFET power switch is intended for high-side load-switching applications. This switch operates with inputs from +2.7V to +5.5V, making it ideal for both +3V and +5V systems. Internal current-limiting circuitry protects the input supply against overload. Thermal overload protection limits power dissipation and junction temperature. The MAX893L’s maximum programmed current limit is 1.2A. The typical short-circuit current is 1.5 times the programmed current; therefore, a 1.2A programmed limit will result in a 1.8A short-circuit current limit. The current limit through the switch is programmed with a resistor from SET to ground. The quiescent supply current is a low 13µA. When the switch is off, the supply current decreases to 0.1µA. The MAX893L is available in an 8-pin SO package. MAX893L 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown ABSOLUTE MAXIMUM RATINGS IN to GND ................................................................-0.3V to +6V ON, FAULT to GND .................................................-0.3V to +6V SET, OUT to GND ...................................... -0.3V to (VIN + 0.3V) Maximum Continuous Short-Circuit Switch Current .............2.0A Continuous Power Dissipation (TA = +70°C) SO (derate 5.88mW/°C above +70°C) .........................471mW Operating Temperature Range MAX893LESA ...................................................-40°C to +85°C Storage Temperature Range ........................... -65°C to +150°C Lead Temperature (soldering, 10sec) .............................+300°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 in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = 3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Operating Voltage MIN TYP 2.7 MAX UNITS 5.5 V Quiescent Current VIN = 5V, ON = GND, IOUT = 0 13 20 µA Off-Supply Current ON = IN, VIN = VOUT = 5.5V 0.03 1 µA Off-Switch Current ON = IN, VIN = 5.5V, VOUT = 0 0.04 15 µA Undervoltage Lockout Rising edge, 1% hysteresis V On-Resistance Current-Limit-Amplifier Threshold 2.4 2.6 VIN = 4.5V 70 125 VIN = 3.0V 88 160 1.240 1.302 VSET required to turn the switch off (Note 1) 2.0 1.178 mΩ V Maximum Programmable Continuous Output Current Limit 1.2 A Short-Circuit Current 1.8 A IOUT to ISET Current Ratio IOUT = 500mA, VOUT > 1.6V ON Input Voltage Low VIN = 2.7V to 5.5V ON Input Voltage High 920 VIN = 2.7V to 3.6V 2.0 VIN = 4.5V to 5.5V 2.4 1080 1250 A/A 0.8 V V ON Input Leakage Current V ON = 5.5V 0.01 1 µA ISET Bias Current VSET = 1.24V, IOUT = 0; VIN = VOUT 0.5 3 µA FAULT Logic Output Voltage Low ISINK = 1mA, VSET = 1.4V FAULT Logic Output High Leakage Current V FAULT = 5.5V, VSET = 1V Slow Current-Loop Response Time 20% current overdrive, VIN = 5V 5 VIN = 5V, IOUT = 500mA 80 VIN = 3V, IOUT = 500mA 115 0.05 Fast Current-Loop Response Time Turn-On Time Turn-Off Time 2 0.4 V 1 µA µs 2 VIN = 5V, IOUT = 500mA 2 4 _______________________________________________________________________________________ µs 200 µs µs 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown MAX893L ELECTRICAL CHARACTERISTICS (VIN = 3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER CONDITIONS Operating Voltage MIN 3.0 TYP MAX UNITS 5.5 V Quiescent Current VIN = 5V, ON = GND, IOUT = 0 30 µA Off-Supply Current ON = IN, VIN = VOUT = 5.5V 2.2 µA Off-Switch Current ON = IN, VIN = 5.5V, VOUT = 0 15 µA Undervoltage Lockout Rising edge, 1% hysteresis 2.9 V On-Resistance 2.0 VIN = 4.5V 125 VIN = 3.0V 160 mΩ Current-Limit-Amplifier Threshold VSET required to turn the switch off (Note 1) 1.14 1.34 V IOUT to ISET Current Ratio IOUT = 500mA, VOUT > 1.6V 865 1300 A/A FAULT Logic Output Voltage Low ISINK = 1mA, VSET = 1.4V 0.4 V Turn-On Time VIN = 5V, IOUT = 500mA 200 µs Turn-Off Time VIN = 5V, IOUT = 500mA 20 µs 1 Note 1: Tested with IOUT = 100mA and VSET raised until VIN - VOUT ≥ 0.8V. Note 2: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) QUIESCENT CURRENT vs. INPUT VOLTAGE QUIESCENT CURRENT vs. TEMPERATURE 13 8 6 4 VIN = 3V 12 11 10 1 0.1 0.01 9 2 0 8 1 2 3 4 5 6 0.001 -40 -20 0 20 40 60 80 -40 100 -20 0 20 40 60 INPUT VOLTAGE (V) TEMPERATURE (°C) TEMPERATURE (°C) OFF-SWITCH CURRENT vs. TEMPERATURE NORMALIZED ON-RESISTANCE vs. TEMPERATURE IOUT/ISET RATIO vs. ILIMIT 1.2 10 1 1.1 1.0 0.9 100 120 140 80 100 1400 1200 IOUT/ISET RATIO NORMALIZED RON 100 IOUT = 1/2 ILIMIT VIN = 5V 80 MAX89L toc06 1.3 MAX893L toc04 1000 MAX893L toc05 0 OFF-SWITCH CURRENT (nA) OFF-SUPPLY CURRENT (nA) 10 MAX893L toc03 VIN = 5V QUIESCENT CURRENT (µA) QUIESCENT CURRENT (µA) 12 10 MAX89L toc02 ON = GND IOUT = 0 OFF-SUPPLY CURRENT vs. TEMPERATURE 14 MAX89L toc01 14 1000 800 600 0.8 400 0.7 200 0.1 0.6 0.01 -20 0 20 40 60 80 -20 20 0 40 60 80 100 0 20 40 60 80 100 TEMPERATURE (°C) TEMPERATURE (°C) ILIMIT (%) NORMALIZED OUTPUT CURRENT vs. OUTPUT VOLTAGE TURN-ON TIME vs. TEMPERATURE TURN-OFF TIME vs. TEMPERATURE 1.2 130 ILIMIT = 1.2A 1.0 ILOAD = ILIMIT 140 6 ILOAD = ILIMIT 5 VIN = 3V 120 0.6 4 tOFF (µs) tON (µs) 0.8 MAX893L toc09 150 MAX893L toc07 1.4 110 100 90 0.4 VIN = 5V 3 2 VIN = 5V VIN = 3V 80 0.2 1 70 VIN = 5V 0 60 0 1 2 3 4 OUTPUT VOLTAGE (V) 4 0 -40 100 MAX893L toc08 -40 NORMALIZED OUTPUT CURRENT MAX893L 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown 5 6 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 0 -40 -20 0 20 40 60 TEMPERATURE (°C) _______________________________________________________________________________________ 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown OUTPUT OVERLOAD (SLOW-LOOP RESPONSE) A MAX893L toc11 MAX893L toc10 OUTPUT SHORT CIRCUIT (FAST-LOOP RESPONSE) A C C 0V VOUT 0V B 0A B IOUT 0V 2µs/div CIN = 100µF, COUT = 0.1µF A: VIN, 1V/div, AC-COUPLED 2µs/div CIN = 100µF, COUT = 0.1µF A: VIN, 1V/div, AC-COUPLED B: IOUT, 1A/div C: VOUT, 5V/div SWITCH TURN-ON TIME B: IOUT, 2A/div C: VOUT, 5V/div MAX893L toc14 MAX893L toc13 SWITCH TURN-OFF TIME A A 0V 0V B B 0V 0V 20µs/div VIN = 5V, IOUT = ILIMIT/2 A: VON, 2V/div B: VOUT, 2V/div 1µs/div VIN = 5V, IOUT = ILIMIT/2 A: VON, 2V/div B: VOUT, 2V/div _______________________________________________________________________________________ 5 MAX893L ____________________________Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown MAX893L Pin Description PIN NAME FUNCTION 1, 2 IN Input. P-channel MOSFET source. Bypass IN with a 1µF capacitor to ground. 3 ON Active-Low Switch On Input. A logic low turns the switch on. 4 GND Ground 5 SET Set Current-Limit Input. A resistor from SET to ground sets the current limit for the switch. RSET = 1.34 · 103 / ILIMIT, where ILIMIT is the desired current limit in amperes. 6, 7 OUT Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1µF capacitor to ground. 8 FAULT Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature exceeds +165°C. Detailed Description The MAX893L P-channel MOSFET power switch limits output current to a programmed level. When the output current is increased beyond the programmed current limit, or 1.2A (IMAX), the current also increases through the replica switch (I OUT / 1080) and through R SET (Figure 1). The current-limit error amplifier compares the voltage across RSET to the internal 1.24V reference, and regulates the current to the programmed current limit (ILIMIT). This switch is not bidirectional; therefore, the input voltage must be higher than the output voltage. P IN OUT MAX893L P FAULT N REPLICA AMPLIFIER ON P SET Setting the Current Limit ON The MAX893L features internal current-limiting circuitry with a maximum programmable value (IMAX) of 1.2A. For best performance, set the current limit (I LIMIT ) between 0.2A ≤ ILIMIT ≤ 1.2A. This current limit remains in effect throughout the input supply-voltage range. Program the current limit with a resistor (R SET) from SET to ground (Figure 2) as follows: ISET = ILIMIT / 1080 RSET = 1.24V / ISET = 1.34 · 103 / ILIMIT where ILIMIT is the desired current limit. CURRENT-LIMIT AMPLIFIER 1.24V RSET HOT ON CONTROL CIRCUITRY GND Figure 1. Functional Diagram Short-Circuit Protection The MAX893L is a short-circuit protected switch. In the event of an output short circuit or a current overload condition, the current through the switch is limited by the internal current-limiting error amplifier to 1.5 · ILIMIT. The short-circuit current is typically 1.8A for a programmed current limit of 1.2A. When the short-circuit condition is removed, the replica error amplifier will set the current limit back to ILIMIT. 6 For a high ∆VDS/∆t during an output short-circuit condition, the switch turns off and disconnects the input supply from the output. The current-limiting amplifier then slowly turns the switch on with the output current limited to 1.5 · ILIMIT. When the short-circuit condition is removed, the current limit is set back to ILIMIT. See Output ShortCircuit (Fast-Loop Response) and Output Overload (Slow-Loop Response) in the Typical Operating Characteristics. _______________________________________________________________________________________ 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown OUT IN MAX893L INPUT VOLTAGE +5V VOUT MAX893L 100k SET RSET BLANKED SIGNAL TO µP GND Figure 2. Setting the Current Limit R 100k C 0.1µF MAX893L ON/OFF GND FAULT SET RSET Figure 3. Fault-Blanking Circuit Thermal Shutdown Output Capacitor The MAX893L features thermal shutdown. The switch turns off when the junction temperature exceeds +165°C. Once the device cools by 10°C, the switch turns back on. If the fault condition is not removed, the switch will cycle on and off, resulting in a pulsed output. Connect a 0.1µF capacitor from OUT to GND to prevent inductive parasitics from pulling OUT negative during turn-off. Fault Indicator The MAX893L provides a fault output (FAULT). This open-drain output goes low when in current limit or when the die temperature exceeds +165°C. A 100kΩ pull-up resistor from FAULT to IN provides a logiccontrol signal. Fault Blanking During start-up in USB applications, the MAX893L charges the relatively large USB capacitance. This may activate an unwanted fault signal if the charging current exceeds the programmed current limit. To “blank out” this start-up fault signal, add a simple lowpass RC delay circuit as shown in Figure 3. This circuit provides a 10ms delay. Applications Information Input Capacitor To limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor no more than 5mm from IN to GND. A 1µF ceramic capacitor will be adequate for most applications; however, higher capacitor values will further reduce the voltage drop at the input. Layout and Thermal-Dissipation Considerations To take full advantage of the switch-response time to output short-circuit conditions, it is very important to keep all traces as short as possible to reduce the effect of undesirable parasitic inductance. Place input and output capacitors as close to the device as possible (no more than 5mm). Under normal operating conditions, the package can dissipate and channel heat away. Calculate the maximum power as follows: P = (ILIMIT)2 · RON where RON is the on-resistance of the switch. When the output is short circuited, the voltage drop across the switch equals the input supply. Hence, the power dissipated across the switch increases, as does the die temperature. If the fault condition is not removed, the thermal-shutdown protection circuitry turns the switch off until the die temperature falls by 10°C. A ground plane in contact with the device will help dissipate additional heat. Chip Information TRANSISTOR COUNT: 340 _______________________________________________________________________________________ 7 ________________________________________________________Package Information SOICN.EPS MAX893L 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.