MAXIM MAX891L

19-1223; Rev 0; 4/97
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
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. Thermaloverload protection limits power dissipation and junction 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.
____________________________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)
The MAX891L/MAX892L are available in 8-pin µMAX
packages.
________________________Applications
PCMCIA Slots
______________Ordering Information
PART
TEMP.
RANGE
MAX891LC/D
MAX891LEUA*
MAX892LC/D
MAX892LEUA*
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
Access Bus Slots
Portable Equipment
PINCURRENT
PACKAGE
LIMIT
Dice**
8 µMAX
Dice**
8 µMAX
500mA
500mA
250mA
250mA
* To order these units in tape and reel, add (-T) to the end of the
part number.
** Dice are tested at TA = +25°C.
__________Typical Operating Circuit
__________________Pin Configuration
TOP VIEW
INPUT
IN
OUT
OUTPUT
0.1µF
100k
1µF
IN
MAX891L
MAX892L
FAULT
ON
GND
SET
8 OUT
IN 1
OUT
ON/OFF
IN 2
ON 3
MAX891L
MAX892L
7 OUT
6 FAULT
5 SET
GND 4
µMAX
________________________________________________________________ Maxim Integrated Products
1
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MAX891L/MAX892L
_______________General Description
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches 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 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
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
MIN
Operating Voltage
V
20
µA
0.02
1
µA
0.02
3
µA
2.3
2.6
V
MAX891L
120
225
MAX892L
250
420
MAX891L
150
300
MAX892L
300
500
1.240
1.302
Off-Supply Current
ON = IN, VIN = VOUT = 5.5V
Off-Switch Current
ON = IN, VIN = 5.5V, VOUT = 0V
Undervoltage Lockout
Rising edge, 1% hysteresis
VIN = 4.5V
VIN = 3.0V
Maximum Output Current
2.0
VSET required to turn the switch off (Note 1)
1.178
MAX891L
500
MAX892L
250
IOUT to ISET Current Ratio
VOUT = 1.6V to 2.8V
ON Input Low Voltage
VIN = 2.7V to 5.5V
840
965
1130
MAX892L, IOUT = 125mA
840
965
1130
0.8
2.0
VIN = 4.5V to 5.5V
2.4
ON Input Leakage
V ON = 5.5V
-1
ISET Bias Current
VSET = 1.24V, IOUT = 0mA
FAULT Logic Output Low Voltage
ISINK = 1mA, VSET = 1.4V
Slow-Current-Loop Response Time
Turn-On Time
Turn-Off Time
VIN = 5V
VIN = 5V
100
VIN = 3V
150
0.8
A/A
V
µA
3
µA
0.4
V
1
µA
µs
2
IOUT = 250mA (MAX891L), or 125mA
(MAX892L)
V
1
5
Fast-Current-Loop Response Time
2
0.01
0.05
20% current overdrive, VIN = 5V
mΩ
V
0.5
FAULT Logic Output High Leakage V FAULT = 5.5V, VSET = 1V
mΩ
mA
MAX891L, IOUT = 250mA
VIN = 2.7V to 3.6V
ON Input High Voltage
UNITS
13
VIN = 5V, ON = GND, IOUT = 0mA
On-Resistance
MAX
5.5
Quiescent Current
Current-Limit-Amplifier Accuracy
TYP
2.7
2
_______________________________________________________________________________________
µs
200
20
µs
µs
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
MAX891L/MAX892L
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 = 0mA
50
µA
Off-Supply Current
ON = IN, VIN = VOUT = 5.5V
2.2
µA
Off-Switch Current
ON = IN, VIN = 5.5V, VOUT = 0V
8
µA
Undervoltage Lockout
Rising edge, 1% hysteresis
2.9
V
VIN = 4.5V
On-Resistance
2.0
MAX891L
225
MAX892L
420
MAX891L
300
MAX892L
500
On-Resistance
VIN = 3.0V
Current-Limit-Amplifier Accuracy
VSET required to turn the switch off (Note 1)
1.14
1.34
MAX891L, IOUT = 250mA
805
1210
MAX892L, IOUT = 125mA
805
1210
mΩ
mΩ
V
IOUT to ISET Current Ratio
VOUT = 1.6V to 2.8V
FAULT Logic Output Low Voltage
ISINK = 1mA, VSET = 1.4V
0.4
V
Turn-On Time
VIN = 5V
200
µs
Turn-Off Time
VIN = 5V
20
µs
0.25
A/A
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.
_______________________________________________________________________________________
3
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)
QUIESCENT CURRENT
vs. TEMPERATURE
4
2
VIN = 3V
10
9
1
2
3
4
5
-20
20
0
40
60
80
INPUT VOLTAGE (V)
TEMPERATURE (°C)
OFF-SWITCH LEAKAGE CURRENT
vs. TEMPERATURE
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
0.03
0.02
0.01
0
-40
-20
20
0
40
60
80
1.2
1200
1.1
1000
1.0
0.9
60
400
0.7
200
-20
0
20
40
60
80
100
0
20
40
60
80
100
ILIMIT (%)
NORMALIZED OUTPUT CURRENT
vs. OUTPUT VOLTAGE
TURN-ON TIME
vs. TEMPERATURE
TURN-OFF TIME
vs. TEMPERATURE
MAX890-06A
260
ILOAD = ILIM
240
4
MAX981/2/3-07
1.0
VIN = 3V
160
140
120
VIN = 5V
100
0.2
VIN = 5V
VIN = 3V
180
tOFF (µs)
tON (µs)
0.4
2
1
80
0
60
1
ILOAD = ILIM
140
3
200
0.6
120
VIN = 5V
220
0.8
100
0
-40
TEMPERATURE (°C)
ILIMIT
80
600
TEMPERATURE (°C)
1.2
0
40
800
0.8
100
20
0
1400
0.6
-40
-20
IOUT/ISET RATIO
vs. ILIMIT
IOUT/ISET RATIO
NORMALIZED RON
0.04
100
MAX980-05
ILOAD = 1/2ILIM
0.05
0.02
TEMPERATURE (°C)
1.3
MAX980-04
0.06
0.03
0
-40
6
0.04
0.01
7
0
LEAKAGE CURRENT (µA)
11
8
0
2
3
4
OUTPUT VOLTAGE (V)
4
12
0.05
MAX981/2/3-06
6
VIN = 5V
MAX981/2/3-08
8
OFF-SUPPLY CURRENT (µA)
10
0.06
MAX981/2/3-02
13
QUIESCENT CURRENT (µA)
12
QUIESCENT CURRENT (µA)
14
MAX981/2/3-01
14
OFF-SUPPLY CURRENT
vs. TEMPERATURE
MAX980-03
QUIESCENT CURRENT
vs. INPUT VOLTAGE
NORMALIZED OUTPUT CURRENT
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
5
6
0
-40
-20
0
20
40
60
TEMPERATURE (°C)
80
100
-40
-20
0
20
40
60
TEMPERATURE (°C)
_______________________________________________________________________________________
80
100
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)
CURRENT-LIMIT RESPONSE
(MAX891L, RL = 0.8Ω)
CURRENT-LIMIT RESPONSE
(MAX891L, RL = 0.5Ω)
A
5V
B
B
C
5V
A
0A
0A
C
0V
0V
2µs/div
CIN = 47µF, COUT = 0.1µF
A: VIN, 500mV/div, AC COUPLED
1µs/div
CIN = 47µF, COUT = 0.1µF
A: VIN, 500mV/div, AC COUPLED
B: IOUT, 2A/div
C: VOUT, 5V/div
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 TIMING CHARACTERISTICS
SWITCH TURN-OFF TIME
A
0A
A
B
0V
0V
C
0V
B
D
0V
0V
2µs/div
VIN = 5V, IOUT = ILIM
A: VON, 2V/div
B: VOUT, 2V/div
50µs/div
VIN = 5V
A: ILOAD, 0.1A/div
B: VON, 5V/div
C: VOUT, 5V/div
D: VFAULT, 5V/div
_______________________________________________________________________________________
5
MAX891L/MAX892L
____________________________Typical Operating Characteristics (continued)
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
______________________________________________________________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. See Setting the
Current Limit section.
6
FAULT
Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature
exceeds +135°C.
7, 8
OUT
Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1µF capacitor to ground.
_______________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 (I OUT /965) and through
RSET (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 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.
MAX891L
MAX892L
P
IN
OUT
P
FAULT
N
REPLICA
AMPLIFIER
ON
P
Setting the Current Limit
SET
The MAX891L/MAX892L feature internal current-limiting circuitry with maximum programmable values
(IMAX) of 500mA and 250mA, respectively. For best
performance, set the current limit (I LIMIT ) between
0.2IMAX ≤ ILIMIT ≤ IMAX. 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 / 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 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 sets the current limit back to
ILIMIT.
6
ON
CURRENT-LIMIT
AMPLIFIER
1.24V
RSET
HOT
ON
CONTROL
CIRCUITRY
GND
Figure 1. Functional Diagram
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 x ILIMIT. When the fault condition is removed, the
current limit is set back to ILIMIT. Refer to the CurrentLimit Response graphs in the Typical Operating
Characteristics.
_______________________________________________________________________________________
Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
MAX891L
MAX892L
Layout and Thermal-Dissipation
Consideration
SET
RSET
GND
Figure 2. Setting the Current Limit
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 100kΩ pull-up resistor
from FAULT to IN provides a logic-control signal.
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 dissipates 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
__________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.
_______________________________________________________________________________________
7
MAX891L/MAX892L
Output Capacitor
Connect a 0.1µF capacitor from OUT to GND. One
function of this capacitor is to prevent inductive parasitics from pulling OUT negative during turn-off.
__________________________________________________Tape-and-Reel Information
4.0 ±0.1
1.0 ±0.1
2.0 ±0.05
1.5 +0.1/-0.0 DIAMETER
1.75 ±0.1
A
3.5 ±0.05
8.0 ±0.3
2.2 ±0.1
0.5 RADIUS
TYPICAL
4.0 ±0.1
A0
A
Bo
0.30 ±0.05
0.8 ±0.05
1.0 MINIMUM
Ko
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.
0.30R MAX.
________________________________________________________Package Information
8LUMAXD.EPS
MAX891L/MAX892L
Current-Limited, High-Side
P-Channel Switches 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
© 1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.