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 pro-
tection limits power dissipation and junction tempera-
tures.
The MAX890L’s maximum current limit is 1.2A. The cur-
rent limit through the switch is programmed with a
resistor from SET to ground. The quiescent supply cur-
rent is a low 10µA. When the switch is off, the supply
current decreases to 0.1µA.
The MAX890L is available in an 8-pin SO package.
________________________Applications
PCMCIA Slots
Access Bus Slots
Portable Equipment
____________________________Features
♦+2.7V to +5.5V Input Range
♦Programmable Current Limit
♦Low Quiescent Current
10µA (typ) at VIN = +3.3V
0.1µA (typ) with Switch Off
♦Thermal Shutdown
♦FAULT Indicator Output
♦0.09Ω(typ) On-Resistance
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
________________________________________________________________ Maxim Integrated Products 1
1
2
8
7
FAULT
OUT
OUT
SET
IN
IN
ON
GND
MAX890L
SO
TOP VIEW
3
4
6
5
Pin Configuration
MAX890L
1µF
0.1µF
100kΩ
IN OUTPUTOUTINPUT
IN OUT
FAULT ON ON/OFF
RSET
GND SET
Typical Operating Circuit
19-1146; Rev 3; 3/00
PART*
MAX890LC/D 0°C to +70°C
TEMP.
RANGE
PIN-
PACKAGE
Dice**
Ordering Information
* To order this unit in tape and reel, add (-T) to the end of the part
number.
** Dice are tested at TA= +25°C.
CURRENT
LIMIT
1.2A
1.2AMAX890LESA -40°C to +85°C 8 SO
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch 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 ..................................1.5A
Continuous Power Dissipation (TA= +70°C)
SO (derate 5.88mW/°C above +70°C) ..........................471mW
Operating Temperature Range
MAX890LESA ....................................................-40°C to +85°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10s) . ...............................+300°C
ON = IN, VIN = VOUT = 5.5V
VIN = 5V
VIN = 3V, IOUT = 500mA
VIN = 5V, ON = GND, IOUT = 0
VIN = 5V, IOUT = 500mA
20% current overdrive, VCC = 5V
VFAULT = 5.5V, VSET = 1V
VIN = 2.7V to 3.6V
VIN = 2.7V to 5.5V
ISINK = 1mA, VSET = 1.4V
VSET = 1.24V, IOUT = 0; VIN = VOUT
IOUT = 500mA, VOUT > 1.6V
ON = IN, VIN = 5.5V, VOUT = 0
Rising edge, 1% hysteresis
VIN = 4.5V
VON = 5.5V
VSET required to turn the switch off (Note 1)
VIN = 4.5V to 5.5V
CONDITIONS
µs25Turn-Off Time
µs
185
Turn-On Time 120 200
µs2Fast-Current-Loop Response Time
µs5Slow-Current-Loop Response Time
µA0.05 1
FAULT Logic Output High Leakage Current
V0.4
FAULT Logic Output Low Voltage
µA0.5 3ISET Bias Current
µA0.01 1
ON Input Leakage Current
V
2.4
ON Input High Voltage
µA0.03 1Off-Supply Current
µA13 20
V2.7 5.5Operating Voltage
Quiescent Current
2.0
V0.8
ON Input Low Voltage
A/A970 1110 1300IOUT to ISET Current Ratio
A1.2Maximum Output Current Limit
µA0.04 15Off-Switch Current
V2.0 2.4 2.6Undervoltage Lockout
75 130
V1.178 1.240 1.302Current-Limit-Amplifier Threshold
UNITSMIN TYP MAXPARAMETER
VIN = 3.0V mΩ
90 150
On-Resistance
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________ 3
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.
ON = IN, VIN = VOUT = 5.5V
VIN = 5V
VIN = 5V, ON = GND, IOUT = 0
ISINK = 1mA, VSET = 1.4V
IOUT = 500mA, VOUT > 1.6V
ON = IN, VIN = 5.5V, VOUT = 0
Rising edge, 1% hysteresis
VIN = 4.5V
VSET required to turn the switch off (Note 1)
CONDITIONS
VIN = 3.0V mΩ
150
µs200
On-Resistance
Turn-On Time
V0.4
FAULT Logic Output Low Voltage
µA2.2Off-Supply Current
µA50
V3.0 5.5Operating Voltage
Quiescent Current
A/A925 1390IOUT to ISET Current Ratio
µA15Off-Switch Current
V2.0 2.9Undervoltage Lockout
130
V1.14 1.34Current-Limit-Amplifier Threshold
UNITSMIN TYP MAXPARAMETER
ELECTRICAL CHARACTERISTICS
(VIN = +3V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
VIN = 5V µs120Turn-Off Time
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
4 _______________________________________________________________________________________
-40 0 20 60 8040-20 100
OFF-SWITCH CURRENT
vs. TEMPERATURE
MAX890 toc04
TEMPERATURE (°C)
OFF-SWITCH CURRENT (nA)
1000
0.01
1
10
0.1
100
0.6
-40 -20 4020 100
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
0.8
MAX890 toc05
TEMPERATURE (°C)
NORMALIZED RON
06080
1.2
1.0
0.7
1.3
1.1
0.9
IOUT = 1/2ILIMIT
0
020 8060 140
IOUT/ISET RATIO
vs. ILIMIT
400
MAX890 toc06
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 toc07
OUTPUT VOLTAGE (V)
NORMALIZED OUTPUT CURRENT
01 234 56
ILIMIT
VIN = 5V
260
60
TURN-ON TIME
vs. TEMPERATURE
100
220
MAX890 toc08
TEMPERATURE (°C)
tON (µs)
180
140
240
80
200
160
120
ILOAD = ILIMIT
VIN = 3V
VIN = 5V
-40 -20 4020 10006080
0
TURN-OFF TIME
vs. TEMPERATURE
2
8
MAX890 toc09
TEMPERATURE (°C)
tOFF (µs)
6
4
1
7
5
3
ILOAD = ILIMIT
VIN = 3V
VIN = 5V
-40 -20 4020 10006080
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
0
2
4
6
8
10
12
14
QUIESCENT CURRENT
vs. INPUT VOLTAGE
MAX890 toc01
INPUT VOLTAGE (V)
01 234 56
ON = GND
IOUT = 0
QUIESCENT CURRENT (µA)
7
-40 -20 4020 100
QUIESCENT CURRENT
vs. TEMPERATURE
9
MAX890 toc02
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
06080
13
11
8
14
12
10
VIN = 3V
VIN = 5V
100
0.01
-40 -20 2006040 80 100
OFF-SUPPLY CURRENT
vs. TEMPERATURE
0.1
MAX890 toc03
TEMPERATURE (°C)
OFF-SUPPLY CURRENT (nA)
1
10
VIN = 5V
A: IOUT = 0mA TO 750mA,
0.5A/div
LOAD-TRANSIENT RESPONSE
A
B
0A
0V
5ms/div
B: VOUT RIPPLE,
200mV/div, AC COUPLED
MAX890 toc12
VIN = 5V, IOUT = ILIMIT
A: VON, 2V/div
B: VOUT, 2V/div
SWITCH TURN-ON TIME
A
B
20µs/div
MAX890 toc13
CIN = 100µF, COUT = 0.1µF
A: VIN, 1V/div, AC-COUPLED
OUTPUT SHORT-CIRCUIT
(FAST LOOP RESPONSE)
A5V
B
C
0V
2µs/div
0A
B: IOUT, 5A/div
C: VOUT, 2V/div
MAX890 toc11
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________ 5
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
SWITCH TURN-OFF TIME
A
B
0V
0V
2µs/div
VIN = 5V, IOUT = ILIMIT
A: VON, 2V/div
B: VOUT, 2V/div
MAX890 toc14
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
6 _______________________________________________________________________________________
Pin Description
Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1µF capacitor to ground.
OUT6, 7
Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature
exceeds +135°C.
FAULT
8
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.
SET5
GroundGND4
PIN
Active-Low Switch On Input. A logic low turns the switch on.
ON
3
Input. P-channel MOSFET source. Bypass IN with a 1µF capacitor to ground.
IN1, 2
FUNCTIONNAME
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 (IOUT/1110) and through RSET
(Figure 1). The current-limit error amplifier compares
the voltage across RSET to the internal +1.24V refer-
ence, and regulates the current back to the lesser of
the programmed limit (ILIMIT) or 1.2A.
This switch is not bidirectional; therefore, the input volt-
age must be higher than the output voltage.
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 (ILIMIT)
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.
Short-Circuit Protection
The MAX890L is a short-circuit-protected switch. In the
event of an output short circuit or current-overload con-
dition, 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 condi-
tion, the switch turns off and disconnects the input supply
from the output. The current-limiting amplifier then slow-
ly 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 Short-
Circuit Fast-Loop Response and Output Over-Load
MAX890L
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
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________ 7
Slow-Loop Response in the Typical Operating
Characteristics.
Thermal Shutdown
The MAX890L features 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 MAX890L provides a fault output (FAULT). This
open-drain output goes low when in current limit or
when the die temperature exceeds +135°C. A 100kΩ
pull-up resistor from FAULT to IN provides a logic-
control signal.
Applications Information
Input Capacitor
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor 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.
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 can
dissipate and channel heat away. Calculate the maxi-
mum 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 10°C. A
ground plane in contact with the device will help dissi-
pate additional heat.
Chip Information
TRANSISTOR COUNT: 396
MAX890L
SET
RSET
GND
Figure 2. Setting the Current Limit
MAX890L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
________________________________________________________Package Information
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.
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