MAXIM MAX890LC/D

19-1146; Rev 2; 11/98
1A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
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 1A. The current limit through the switch is programmed with a
resistor from SET to ground. The quiescent supply current 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.
____________________________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
________________________Applications
Ordering Information
PCMCIA Slots
PART*
Access Bus Slots
MAX890LC/D
MAX890LESA
Portable Equipment
TEMP.
RANGE
0°C to +70°C
-40°C to +85°C
PINPACKAGE
Dice**
8 SO
CURRENT
LIMIT
1A
1A
* To order this unit 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
IN
MAX890L
IN 2
100kΩ
1µF
8 FAULT
IN 1
OUT
FAULT
ON
GND
SET
ON/OFF
RSET
MAX890L
7 OUT
ON 3
6 OUT
GND 4
5 SET
SO
________________________________________________________________ Maxim Integrated Products
1
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MAX890L
General Description
MAX890L
1A, 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 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, 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
75
130
VIN = 3.0V
90
150
1.240
1.302
VSET required to turn the switch off (Note 1)
2.0
1.178
Maximum Output Current Limit
1
IOUT to ISET Current Ratio
IOUT = 500mA, VOUT > 1.6V
ON Input Low Voltage
VIN = 2.7V to 5.5V
ON Input High Voltage
970
VIN = 2.7V to 3.6V
2.0
VIN = 4.5V to 5.5V
2.4
1110
V ON = 5.5V
0.01
ISET Bias Current
VSET = 1.24V, IOUT = 0; VIN = VOUT
0.5
FAULT Logic Output Low Voltage
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, VCC = 5V
Turn-On Time
Turn-Off Time
0.05
A/A
0.8
V
1
µA
3
µA
0.4
V
1
µA
5
VIN = 5V, IOUT = 500mA
120
VIN = 3V, IOUT = 500mA
185
2
5
Note 1: Tested with IOUT = 100mA and VSET raised until VIN - VOUT ≥ 0.8V.
2
1300
µs
2
VIN = 5V
V
A
V
ON Input Leakage
Fast-Current-Loop Response Time
mΩ
_______________________________________________________________________________________
µs
200
µs
µs
1A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX890L
ELECTRICAL CHARACTERISTICS
(VIN = 3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
Operating Voltage
MIN
2.9
TYP
MAX
UNITS
5.5
V
Quiescent Current
VIN = 5V, ON = GND, IOUT = 0
50
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
130
VIN = 3.0V
150
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
925
1390
A/A
FAULT Logic Output Low Voltage
ISINK = 1mA, VSET = 1V
0.4
V
Turn-On Time
VIN = 5V
200
µs
Turn-Off Time
VIN = 5V
20
µs
1
Note 2: Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
13
8
6
4
2
VIN = 5V
12
11
VIN = 3V
10
9
10
1
0.1
8
7
1
2
3
4
5
0.01
-40
6
-20
20
0
40
60
INPUT VOLTAGE (V)
TEMPERATURE (°C)
OFF-SWITCH CURRENT
vs. TEMPERATURE
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
1
20
40
60
80
100
1400
1.2
1.1
1200
IOUT/ISET RATIO
10
0
IOUT/ISET RATIO
vs. ILIMIT
IOUT = 1/2ILIMIT
NORMALIZED RON
100
-20
TEMPERATURE (°C)
1.3
MAX890L toc04
1000
-40
100
80
MAX890-05
0
1.0
0.9
MAX890-06
0
OFF-SWITCH CURRENT (nA)
OFF-SUPPLY CURRENT (nA)
10
100
MAX890-02
14
MAX890-01
ON = GND
IOUT = 0
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
14
12
OFF-SUPPLY CURRENT
vs. TEMPERATURE
QUIESCENT CURRENT
vs. TEMPERATURE
MAX890L toc03
QUIESCENT CURRENT
vs. INPUT VOLTAGE
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
ILOAD = ILIMIT
240
220
160
140
0.4
ILOAD = ILIMIT
7
6
tOFF (µs)
tON (µs)
0.6
180
140
8
VIN = 3V
200
0.8
120
MAX980-08
ILIMIT
1.0
260
MAX890-06A
1.2
VIN = 5V
5
4
VIN = 3V
3
VIN = 5V
120
2
100
0.2
VIN = 5V
1
80
0
0
60
0
1
2
3
4
OUTPUT VOLTAGE (V)
4
0
-40
100
MAX980-07
-40
NORMALIZED OUTPUT CURRENT
MAX890L
1A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
5
6
-40
-20
0
20
40
60
TEMPERATURE (°C)
80
100
-40
-20
0
20
40
60
TEMPERATURE (°C)
_______________________________________________________________________________________
80
100
1A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
CURRENT-LIMIT RESPONSE
(RL = 0.6Ω)
CURRENT-LIMIT RESPONSE
(RL = 0.3Ω)
A
5V
A
B
5V
B
0A
C
C
0V, 0A
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, 2V/div
B: IOUT, 5A/div
C: VOUT, 2V/div
LOAD-TRANSIENT RESPONSE
A
0A
0V
B
5ms/div
VIN = 5V
A: IOUT = 0mA TO 750mA,
0.5A/div
B: VOUT RIPPLE,
200mV/div, AC COUPLED
SWITCH TURN-OFF TIME
SWITCH TURN-ON TIME
A
A
0V
B
B
0V
2µs/div
20µs/div
VIN = 5V, IOUT = ILIMIT
A: VON, 2V/div
B: VOUT, 2V/div
VIN = 5V, IOUT = ILIMIT
A: VON, 2V/div
B: VOUT, 2V/div
_______________________________________________________________________________________
5
MAX890L
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
1A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX890L
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 = 1.38 x 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 +135°C.
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 1A (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 1A.
This switch is not bidirectional; therefore, the input voltage must be higher than the output voltage.
P
IN
OUT
MAX890L
P
FAULT
N
REPLICA
AMPLIFIER
ON
P
SET
Setting the Current Limit
The MAX890L features internal current-limiting circuitry
with a maximum programmable value (IMAX) of 1A. 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 (R SET) 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.
ON
CURRENT-LIMIT
AMPLIFIER
1.24V
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
6
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 Short-Circuit
Slow-Loop Response in the Typical Operating
Characteristics.
_______________________________________________________________________________________
1A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX890L
Layout and Thermal-Dissipation
Consideration
SET
RSET
GND
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
Figure 2. Setting the Current Limit
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 logiccontrol signal.
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 dissipate additional heat.
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 1µF ceramic capacitor will be adequate for
most applications; however, higher capacitor values
will further reduce the voltage drop at the input.
_______________________________________________________________________________________
7
MAX890L
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.
________________________________________________________Package Information
SOICN.EPS
MAX890L
1A, 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
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.