_______________General Description
The MAX891L/MAX892L smart, low-voltage, P-channel,
MOSFET power switches are intended for high-side
load-switching applications. These switches operate
with inputs from 2.7V to 5.5V, making them ideal for
both 3V and 5V systems. Internal current-limiting circuitry
protects the input supply against overload. Thermal-
overload protection limits power dissipation and junc-
tion temperatures.
The MAX891L/MAX892L’s maximum current limits are
500mA and 250mA, respectively. The current limit
through the switch is programmed with a resistor from
SET to ground. When the switch is on, the quiescent
supply current is a low 13µA. When the switch is off, the
quiescent current decreases to 0.1µA.
The MAX891L/MAX892L are available in 8-pin µMAX
packages.
________________________Applications
PCMCIA Slots
Access Bus Slots
Portable Equipment
____________________________Features
♦Ultra-Small µMAX Package—Only 1.11mm High
♦2.7V to 5.5V Input Range
♦Programmable Current Limit
♦Low 13µA Quiescent Current at VIN = 3.3V,
0.1µA Switch Off
♦Thermal Shutdown
♦FAULT Indicator Output
♦On-Resistances:
0.12Ω(MAX891L)
0.25Ω(MAX892L)
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
________________________________________________________________
Maxim Integrated Products
1
1
2
8
7
OUT
OUT
FAULT
SET
IN
IN
ON
GND
MAX891L
MAX892L
µMAX
TOP VIEW
3
4
6
5
__________________Pin Configuration
1µF
0.1µF
100k
IN OUTPUTOUTINPUT
IN OUT
FAULT ON ON/OFF
GND SET
MAX891L
MAX892L
__________Typical Operating Circuit
19-1223; Rev 0; 4/97
PART
MAX891LC/D 0°C to +70°C
TEMP.
RANGE PIN-
PACKAGE
Dice**
______________Ordering Information
* To order these units in tape and reel, add (-T) to the end of the
part number.
** Dice are tested at TA= +25°C.
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
CURRENT
LIMIT
500mA
MAX892LC/D 0°C to +70°C Dice** 250mA
MAX891LEUA* -40°C to +85°C 8 µMAX 500mA
MAX892LEUA* -40°C to +85°C 8 µMAX 250mA
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = 3V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°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.
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
MAX891L ..........................................................................0.75A
MAX892L ........................................................................0.375A
Continuous Power Dissipation (TA= +70°C)
µMAX (derate 4.1mW/°C above +70°C) .......................330mW
Operating Temperature Range
MAX891LEUA/MAX892LEUA ............................-40°C to +85°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10sec) ........................... +300°C
20% current overdrive, VIN = 5V
VFAULT = 5.5V, VSET = 1V
ISINK = 1mA, VSET = 1.4V
ON = IN, VIN = VOUT = 5.5V
VSET = 1.24V, IOUT = 0mA
VON = 5.5V
VIN = 5V, ON = GND, IOUT = 0mA
VIN = 4.5V to 5.5V
VIN = 2.7V to 3.6V
VIN = 2.7V to 5.5V
VOUT = 1.6V to 2.8V
MAX891L
VSET required to turn the switch off (Note 1)
MAX891L, IOUT = 250mA
VIN = 3.0V
MAX891L
MAX891L
VIN = 4.5V MAX892L
MAX892L
CONDITIONS
µs5Slow-Current-Loop Response Time µA0.05 1
MAX892L
FAULT Logic Output High Leakage V0.4
MAX892L, IOUT = 125mA
FAULT Logic Output Low Voltage µA0.5 3
IOUT = 250mA (MAX891L), or 125mA
(MAX892L)
ISET Bias Current µA-1 0.01 1
ON Input Leakage
V
2.4
ON Input High Voltage 2.0
VIN = 5V µs
V0.8
2
ON Input Low Voltage
A/A
Fast-Current-Loop Response Time
IOUT to ISET Current Ratio
VIN = 3V
840 965 1130
µs
100 200
Turn-On Time
840 965 1130
VIN = 5V µs
mA
0.8 2 20
Maximum Output Current
Turn-Off Time
250
µA0.02 1Off-Supply Current µA13 20 V2.7 5.5Operating Voltage
Quiescent Current
500 V1.178 1.240 1.302Current-Limit-Amplifier Accuracy
mΩ
On-Resistance
300 500
120 225
250 420
150 300
UNITSMIN TYP MAXPARAMETER
mΩ
150
ON = IN, VIN = 5.5V, VOUT = 0V µA0.02 3Off-Switch Current Rising edge, 1% hysteresis V2.0 2.3 2.6Undervoltage Lockout
On-Resistance
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
_______________________________________________________________________________________ 3
Note 1: Tested with IOUT = 50mA for the MAX891L, 25mA for the MAX892L, and VSET raised until VIN - VOUT ≥0.8V.
Note 2: Parameters to -40°C are guaranteed by design, not production tested.
ELECTRICAL CHARACTERISTICS
(VIN = 3V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
VIN = 5V
VIN = 5V
ISINK = 1mA, VSET = 1.4V
ON = IN, VIN = VOUT = 5.5V
VIN = 5V, ON = GND, IOUT = 0mA
VOUT = 1.6V to 2.8V
VSET required to turn the switch off (Note 1)
MAX891L, IOUT = 250mA
VIN = 3.0V
MAX891L
MAX891L
VIN = 4.5V MAX892L
CONDITIONS
µs0.25 20Turn-Off Time µs200
MAX892L
Turn-On Time V0.4
MAX892L, IOUT = 125mA
FAULT Logic Output Low Voltage
Rising edge, 1% hysteresis
ON = IN, VIN = 5.5V, VOUT = 0V
A/AIOUT to ISET Current Ratio 805 1210
805 1210
V2.0 2.9
µA2.2
Undervoltage Lockout
Off-Supply Current µA50
µA
V3.0 5.5
8
Operating Voltage
Quiescent Current
Off-Switch Current
V1.14 1.34Current-Limit-Amplifier Accuracy
mΩ
On-Resistance
500
225
420
300
UNITSMIN TYP MAXPARAMETER
mΩ
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
4 _______________________________________________________________________________________
0
0.01
0.02
0.03
0.04
0.05
0.06
-40 -20 4020 100
OFF-SWITCH LEAKAGE CURRENT
vs. TEMPERATURE
MAX980-04
TEMPERATURE (°C)
LEAKAGE CURRENT (µA)
0 60 80
0.6 -40 -20 4020 100
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
0.8
MAX980-05
TEMPERATURE (°C)
NORMALIZED RON
0 60 80
1.2
1.0
0.7
1.3
1.1
0.9
ILOAD = 1/2ILIM
00 20 8060 140
IOUT/ISET RATIO
vs. ILIMIT
400
MAX981/2/3-06
ILIMIT (%)
IOUT/ISET RATIO
40 100 120
1200
800
200
1400
1000
600
0
0.2
0.4
0.6
0.8
1.0
1.2
NORMALIZED OUTPUT CURRENT
vs. OUTPUT VOLTAGE
MAX890-06A
OUTPUT VOLTAGE (V)
NORMALIZED OUTPUT CURRENT
0123456
ILIMIT
VIN = 5V
260
60
TURN-ON TIME
vs. TEMPERATURE
100
220
MAX981/2/3-07
TEMPERATURE (°C)
tON (µs)
180
140
240
80
200
160
120
ILOAD = ILIM
VIN = 3V
VIN = 5V
-40 -20 4020 1000 60 80
0
TURN-OFF TIME
vs. TEMPERATURE
1
4
MAX981/2/3-08
TEMPERATURE (°C)
tOFF (µs)
3
2
ILOAD = ILIM
VIN = 3V
VIN = 5V
-40 -20 4020 1000 60 80
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)
0
2
4
6
8
10
12
14
QUIESCENT CURRENT
vs. INPUT VOLTAGE
MAX981/2/3-01
INPUT VOLTAGE (V)
QUIESCENT CURRENT (µA)
0123456
7-40 -20 4020 100
QUIESCENT CURRENT
vs. TEMPERATURE
9
MAX981/2/3-02
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
0 60 80
13
11
8
14
12
10 VIN = 3V
VIN = 5V
0
0.01
0.02
0.03
0.04
0.05
0.06
-40 -20 4020 100
OFF-SUPPLY CURRENT
vs. TEMPERATURE
MAX980-03
TEMPERATURE (°C)
OFF-SUPPLY CURRENT (µA)
0 60 80
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
_______________________________________________________________________________________
5
CIN = 47µF, COUT = 0.1µF
A: VIN, 500mV/div, AC COUPLED
CURRENT-LIMIT RESPONSE
(MAX891L, RL = 0.8Ω)
A 5V
B
C0A
0V
2µs/div B: IOUT, 2A/div
C: VOUT, 5V/div
CIN = 47µF, COUT = 0.1µF
A: VIN, 500mV/div, AC COUPLED
CURRENT-LIMIT RESPONSE
(MAX891L, RL = 0.5Ω)
A5V
B
C0V
1µs/div
0A
B: IOUT, 2A/div
C: VOUT, 5V/div
SWITCH TURN-ON TIME
A
B
20µs/div
VIN = 5V, IOUT = ILIM
A: VON, 2V/div
B: VOUT, 2V/div
SWITCH TURN-OFF TIME
A
B
0V
0V 2µs/div
VIN = 5V, IOUT = ILIM
A: VON, 2V/div
B: VOUT, 2V/div
VIN = 5V
A: ILOAD, 0.1A/div
B: VON, 5V/div C: VOUT, 5V/div
D: VFAULT, 5V/div
SWITCH TIMING CHARACTERISTICS
0V
0V
0A
0V
C
D
A
B
50µs/div
____________________________Typical Operating Characteristics (continued)
(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
6 _______________________________________________________________________________________
______________________________________________________________Pin Description
Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature
exceeds +135°C.
FAULT
6
Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1µF capacitor to ground.OUT7, 8
Set Current-Limit Input. A resistor from SET to ground sets the current limit for the switch. See
Setting the
Current Limit
section.
SET5
GroundGND4
PIN
Active-Low Switch On Input. A logic low turns the switch on.
ON
3Input. P-channel MOSFET source. Bypass IN with a 1µF capacitor to ground.IN1, 2 FUNCTIONNAME
_______________Detailed Description
The MAX891L/MAX892L P-channel MOSFET power
switches limit output current to a user-programmed
level. When the output current is increased beyond
the set current level, the current is also increased
through the replica switch (IOUT/965) and through
RSET (Figure 1). The current-limit error amplifier com-
pares the voltage across RSET to the internal 1.24V ref-
erence and regulates the current back to the lesser of
the programmed current limit (ILIMIT) or the maximum
current limit (IMAX).
These switches are not bidirectional; therefore, the
input voltage must be higher than the output voltage.
Setting the Current Limit
The MAX891L/MAX892L feature internal current-limit-
ing circuitry with maximum programmable values
(IMAX) of 500mA and 250mA, respectively. For best
performance, set the current limit (ILIMIT) between
0.2IMAX ≤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 / IRATIO
RSET = 1.240 / ISET
where ILIMIT is the desired current limit, and IRATIO is
the IOUT to ISET current ratio (965).
Short-Circuit Protection
The MAX891L/MAX892L are short-circuit-protected
switches. In the event of an output short circuit or cur-
rent-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 sets the current limit back to
ILIMIT.
For a high ∆VDS/∆t during an output short-circuit condi-
tion, the switch turns off and disconnects the input sup-
ply 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 the Current-
Limit Response graphs in the
Typical Operating
Characteristics
.
MAX891L
MAX892L
P
P
P
RSET
SET
OUT
GND
1.24V
N
FAULT
ON
ON CURRENT-LIMIT
AMPLIFIER
REPLICA
AMPLIFIER ON
HOT
IN
CONTROL
CIRCUITRY
Figure 1. Functional Diagram
Thermal Shutdown
The MAX891L/MAX892L feature thermal shutdown. The
switch turns off when the junction temperature exceeds
+135°C. Once the device cools by 10°C, 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 MAX891L/MAX892L provide a fault output (FAULT).
This open-drain output goes low when in current limit or
when the die temperature exceeds +135°C. During
start-up, FAULT is low until the switch is fully on and no
over-current condition exists. A 100kΩpull-up resistor
from FAULT to IN provides a logic-control signal.
__________Applications Information
Input Capacitor
To limit input voltage drop during momentary output
short-circuit conditions, connect a capacitor from IN to
GND. A 1µF ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce voltage drop at the input.
Output Capacitor
Connect a 0.1µF capacitor from OUT to GND. One
function of this capacitor is to prevent inductive para-
sitics 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 dissi-
pates and channels heat away. Calculate maximum
power as follows: P = I2LIM x RON
where RON is the on-resistance of the switch.
When the output is short circuited, 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 10°C. A ground plane
in contact with the device helps dissipate additional
heat.
___________________Chip Information
TRANSISTOR COUNT: 396
SUBSTRATE CONNECTED TO GND
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
_______________________________________________________________________________________ 7
MAX891L
MAX892L
SET
RSET
GND
Figure 2. Setting the Current Limit
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
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
________________________________________________________Package Information
__________________________________________________Tape-and-Reel Information
8LUMAXD.EPS
4.0 ±0.1
0.30 ±0.05
0.8 ±0.05
0.30R MAX.
Bo
Ko
2.2 ±0.1
0.5 RADIUS
TYPICAL A0
4.0 ±0.1
2.0 ±0.05
1.5 +0.1/-0.0 DIAMETER 1.75 ±0.1
1.0 ±0.1
A
8.0 ±0.3
3.5 ±0.05
1.0 MINIMUM
A
Ao = 3.1mm ±0.1
Bo = 2.7mm ±0.1
Ko = 1.2mm ±0.1
NOTE: DIMENSIONS ARE IN MM.
AND FOLLOW EIA481-1 STANDARD.
