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19-1146; Rev 3; 3/00
1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown
General Description
The MAX890L 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 temperatures. The MAX890L's maximum current limit is 1.2A. The current limit through the switch is programmed with a resistor from SET to ground. The quiescent supply current is a low 10A. When the switch is off, the supply current decreases to 0.1A. The MAX890L is available in an 8-pin SO package.
____________________________Features
o +2.7V to +5.5V Input Range o Programmable Current Limit o Low Quiescent Current 10A (typ) at VIN = +3.3V 0.1A (typ) with Switch Off o Thermal Shutdown o FAULT Indicator Output o 0.09 (typ) On-Resistance
MAX890L
________________________Applications
PCMCIA Slots Access Bus Slots Portable Equipment
PART* MAX890LC/D MAX890LESA
Ordering Information
TEMP. RANGE 0C to +70C -40C to +85C PINPACKAGE Dice** 8 SO CURRENT LIMIT 1.2A 1.2A
* To order this unit in tape and reel, add (-T) to the end of the part number. ** Dice are tested at TA = +25C.
Typical Operating Circuit
Pin Configuration
TOP VIEW
INPUT IN IN 100k FAULT 1F GND ON SET RSET ON/OFF OUT OUTPUT 0.1F IN 1 IN 2 ON 3 GND 4 8 FAULT
MAX890L
OUT
MAX890L
7 OUT 6 OUT 5 SET
SO
________________________________________________________________ Maxim Integrated Products
1
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1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown MAX890L
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 Switch Current ..................................1.5A Continuous Power Dissipation (TA = +70C) SO (derate 5.88mW/C above +70C) ..........................471mW Operating Temperature Range MAX890LESA ....................................................-40C to +85C Storage Temperature Range ........................... -65C to +150C Lead Temperature (soldering, 10s) . ...............................+300C
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Operating Voltage Quiescent Current Off-Supply Current Off-Switch Current Undervoltage Lockout On-Resistance Current-Limit-Amplifier Threshold Maximum Output Current Limit IOUT to ISET Current Ratio ON Input Low Voltage ON Input High Voltage ON Input Leakage Current ISET Bias Current FAULT Logic Output Low Voltage FAULT Logic Output High Leakage Current Slow-Current-Loop Response Time Fast-Current-Loop Response Time Turn-On Time Turn-Off Time VIN = 5V, IOUT = 500mA VIN = 3V, IOUT = 500mA VIN = 5V 2 IOUT = 500mA, VOUT > 1.6V VIN = 2.7V to 5.5V VIN = 2.7V to 3.6V VIN = 4.5V to 5.5V V ON = 5.5V VSET = 1.24V, IOUT = 0; VIN = VOUT ISINK = 1mA, VSET = 1.4V V FAULT = 5.5V, VSET = 1V 20% current overdrive, VCC = 5V 0.05 5 2 120 185 5 200 2.0 2.4 0.01 0.5 1 3 0.4 1 970 VIN = 5V, ON = GND, IOUT = 0 ON = IN, VIN = VOUT = 5.5V ON = IN, VIN = 5.5V, VOUT = 0 Rising edge, 1% hysteresis VIN = 4.5V VIN = 3.0V VSET required to turn the switch off (Note 1) 1.178 2.0 CONDITIONS MIN 2.7 13 0.03 0.04 2.4 75 90 1.240 1.2 1110 1300 0.8 TYP MAX 5.5 20 1 15 2.6 130 150 1.302 UNITS V A A A V m V A A/A V V A A V A s s s s
2
_______________________________________________________________________________________
1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown
ELECTRICAL CHARACTERISTICS
(VIN = +3V, TA = -40C to +85C, unless otherwise noted.) (Note 2) PARAMETER Operating Voltage Quiescent Current Off-Supply Current Off-Switch Current Undervoltage Lockout On-Resistance Current-Limit-Amplifier Threshold IOUT to ISET Current Ratio FAULT Logic Output Low Voltage Turn-On Time Turn-Off Time VIN = 5V, ON = GND, IOUT = 0 ON = IN, VIN = VOUT = 5.5V ON = IN, VIN = 5.5V, VOUT = 0 Rising edge, 1% hysteresis VIN = 4.5V VIN = 3.0V VSET required to turn the switch off (Note 1) IOUT = 500mA, VOUT > 1.6V ISINK = 1mA, VSET = 1.4V VIN = 5V VIN = 5V 1 1.14 925 2.0 CONDITIONS MIN 3.0 TYP MAX 5.5 50 2.2 15 2.9 130 150 1.34 1390 0.4 200 20 UNITS V A A A V m V A/A V s s
MAX890L
Note 1: Tested with IOUT = 100mA and VSET raised until VIN - VOUT 0.8V. Note 2: Specifications to -40C are guaranteed by design, not production tested.
_______________________________________________________________________________________
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1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown MAX890L
__________________________________________Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
QUIESCENT CURRENT vs. INPUT VOLTAGE
MAX890 toc01
QUIESCENT CURRENT vs. TEMPERATURE
MAX890 toc02
OFF-SUPPLY CURRENT vs. TEMPERATURE
MAX890 toc03
14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) ON = GND IOUT = 0
14 13 QUIESCENT CURRENT (A) VIN = 5V 12 11 VIN = 3V 10 9 8 7 -40 -20 0 20 40 60 80
100
QUIESCENT CURRENT (A)
OFF-SUPPLY CURRENT (nA)
10
1
0.1
0.01 100 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) TEMPERATURE (C)
OFF-SWITCH CURRENT vs. TEMPERATURE
MAX890 toc04
NORMALIZED ON-RESISTANCE vs. TEMPERATURE
MAX890 toc05
IOUT/ISET RATIO vs. ILIMIT
MAX890 toc06
1000
1.3 IOUT = 1/2ILIMIT 1.2 NORMALIZED RON 1.1 1.0 0.9 0.8
1400 1200 IOUT/ISET RATIO 1000 800 600 400 200 0
OFF-SWITCH CURRENT (nA)
100
10
1
0.1 0.7 0.01 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) 0.6 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
0
20
40
60
80
100
120
140
ILIMIT (%)
NORMALIZED OUTPUT CURRENT vs. OUTPUT VOLTAGE
MAX890 toc07
TURN-ON TIME vs. TEMPERATURE
MAX890 toc08
TURN-OFF TIME vs. TEMPERATURE
ILOAD = ILIMIT 7 6 tOFF (s) 5 4 3 VIN = 5V 2 1 0 VIN = 3V VIN = 5V
MAX890 toc09
1.2 NORMALIZED OUTPUT CURRENT 1.0 0.8 0.6 0.4 0.2 VIN = 5V 0 0 1 2 3 4 5 6 OUTPUT VOLTAGE (V) ILIMIT
260 240 220 200 tON (s) 180 160 140 120 100 80 60 -40 -20 0 20 40 60 80 ILOAD = ILIMIT
8
VIN = 3V
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (C)
TEMPERATURE (C)
4
_______________________________________________________________________________________
1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown
____________________________Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
OUTPUT OVER-LOAD (SLOW LOOP RESPONSE)
MAX890 toc10
MAX890L
OUTPUT SHORT-CIRCUIT (FAST LOOP RESPONSE)
MAX890 toc11
A
5V
A
5V
B
B
0A C 0V, 0A 2s/div CIN = 100F, COUT = 0.1F A: VIN, 1V/div, AC-COUPLED B: IOUT, 1A/div C: VOUT, 2V/div C 0V 2s/div CIN = 100F, COUT = 0.1F A: VIN, 1V/div, AC-COUPLED B: IOUT, 5A/div C: VOUT, 2V/div
LOAD-TRANSIENT RESPONSE
MAX890 toc12
SWITCH TURN-ON TIME
MAX890 toc13
A 0A
A
0V B B
5ms/div VIN = 5V A: IOUT = 0mA TO 750mA, 0.5A/div B: VOUT RIPPLE, 200mV/div, AC COUPLED VIN = 5V, IOUT = ILIMIT A: VON, 2V/div B: VOUT, 2V/div
20s/div
SWITCH TURN-OFF TIME
MAX890 toc14
A 0V
B 0V 2s/div VIN = 5V, IOUT = ILIMIT A: VON, 2V/div B: VOUT, 2V/div
_______________________________________________________________________________________
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1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown MAX890L
Pin Description
PIN 1, 2 3 4 5 6, 7 8 NAME IN ON GND SET OUT FAULT FUNCTION Input. P-channel MOSFET source. Bypass IN with a 1F capacitor to ground. Active-Low Switch On Input. A logic low turns the switch on. Ground Set Current-Limit Input. A resistor from SET to ground sets the current limit for the switch. RSET = 1.38 x 103 / ILIMIT, where ILIMIT is the desired current limit in amperes. Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1F capacitor to ground. Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature exceeds +135C.
Detailed Description
The MAX890L 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 /1110) 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 back to the lesser of the programmed limit (ILIMIT) or 1.2A. This switch is not bidirectional; therefore, the input voltage must be higher than the output voltage.
IN P OUT
MAX890L
FAULT P
N
REPLICA AMPLIFIER ON P SET ON CURRENT-LIMIT AMPLIFIER 1.24V
Setting the Current Limit
The MAX890L features internal current-limiting circuitry with a maximum programmable value (IMAX) of 1.2A. For best performance, set the current limit (I LIMIT ) between 0.2 IMAX ILIMIT IMAX. This current limit remains in effect throughout the input supply-voltage range. Program the current limit with a resistor (RSET) from SET to ground (Figure 2) as follows: ISET = ILIMIT / 1110 RSET = 1.24V / I8 = 1.38 x 103 / ILIMIT where ILIMIT is the desired current limit.
RSET
HOT ON CONTROL CIRCUITRY GND
Figure 1. Functional Diagram
Short-Circuit Protection
The MAX890L is a short-circuit-protected switch. In the event of an output short circuit or current-overload condition, the current through the switch is limited by the internal current-limiting error amplifier to 1.5 x ILIMIT. When the fault condition is removed, the replica error amplifier will set the current limit back to ILIMIT.
For a high dVDS/dt 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 x ILIMIT. When the fault condition is removed, the current limit is set back to ILIMIT. Refer to Output ShortCircuit Fast-Loop Response and Output Over-Load
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_______________________________________________________________________________________
1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown
most applications; however, higher capacitor values will further reduce the voltage drop at the input.
MAX890L
Output Capacitor
MAX890L
SET RSET GND
Connect a 0.1F capacitor from OUT to GND. One function of this capacitor is to prevent inductive parasitics from pulling OUT negative during turn-off.
Layout and Thermal-Dissipation Consideration
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 as possible to the device (no more than 5mm). Under normal operating conditions, the package can dissipate and channel heat away. Calculate the maximum power as follows: P = I2LIMIT x 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-overload-protection circuitry turns the switch off until the die temperature falls by 10C. A ground plane in contact with the device will help dissipate additional heat.
Figure 2. Setting the Current Limit
Slow-Loop Response in the Typical Operating Characteristics.
Thermal Shutdown
The MAX890L features thermal shutdown. The switch turns off when the junction temperature exceeds +135C. Once the device cools by 10C, the switch turns back on. If the fault short-circuit condition is not removed, the switch will cycle on and off, resulting in a pulsed output.
Fault Indicator
The MAX890L provides a fault output (FAULT). This open-drain output goes low when in current limit or when the die temperature exceeds +135C. A 100k pull-up resistor from FAULT to IN provides a logiccontrol signal.
Chip Information
TRANSISTOR COUNT: 396
Applications Information
Input Capacitor
To limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from IN to GND. A 1F ceramic capacitor will be adequate for
_______________________________________________________________________________________
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1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown MAX890L
________________________________________________________Package Information
SOICN.EPS
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 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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