General Description
The MAX893L 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-
ture.
The MAX893L’s maximum programmed current limit is
1.2A. The typical short-circuit current is 1.5 times the
programmed current; therefore, a 1.2A programmed
limit will result in a 1.8A short-circuit current limit. The
current limit through the switch is programmed with a
resistor from SET to ground. The quiescent supply cur-
rent is a low 13µA. When the switch is off, the supply
current decreases to 0.1µA.
The MAX893L is available in an 8-pin SO package.
________________________Applications
USB Ports
USB Hubs
PCMCIA Slots
Access Bus Slots
Portable Equipment
____________________________Features
♦+2.7V to +5.5V Input Range
♦Programmable Current Limit
0.2A to 1.2A Range
±20% Accuracy
♦1.2A Continuous Load Current
♦1.8A Short-Circuit Current
♦Low Quiescent Current
13µA at VIN = 3.3V
0.1µA with Switch Off
♦Thermal Shutdown
♦FAULT Indicator Output
♦0.07ΩOn-Resistance
MAX893L
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
MAX893L
SO
TOP VIEW
3
4
6
5
Pin Configuration
MAX893L
1µF
*USB SPECIFICATIONS REQUIRE HIGHER CAPACITANCE.
0.1µF*
100k
IN OUTPUTOUTINPUT
IN OUT
FAULT ON ON/OFF
RSET
GND SET
Typical Operating Circuit
PART TEMP. RANGE PIN-PACKAGE
Ordering Information
MAX893LESA -40°C to +85°C 8 SO
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
19-1450; Rev 0; 7/99
MAX893L
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 Short-Circuit Switch Current .............2.0A
Continuous Power Dissipation (TA= +70°C)
SO (derate 5.88mW/°C above +70°C) .........................471mW
Operating Temperature Range
MAX893LESA ...................................................-40°C to +85°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
ON = IN, VIN = VOUT = 5.5V
VIN = 5V, IOUT = 500mA
VIN = 3V, IOUT = 500mA
VIN = 5V, ON = GND, IOUT = 0
VIN = 5V, IOUT = 500mA
20% current overdrive, VIN = 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
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
µs24Turn-Off Time
µs
115
Turn-On Time 80 200
µs2Fast Current-Loop Response Time
µs5Slow Current-Loop Response Time
µA0.05 1
FAULT Logic Output High Leakage Current
V0.4
FAULT Logic Output Voltage Low
µA0.5 3ISET Bias Current
µA0.01 1
ON Input Leakage Current
V
2.4
ON Input Voltage High
µA0.03 1Off-Supply Current
µA13 20
V2.7 5.5Operating Voltage
Quiescent Current
2.0
V0.8
ON Input Voltage Low
A1.8Short-Circuit Current
A1.2
Maximum Programmable Continuous
Output Current Limit
µA0.04 15Off-Switch Current
V2.0 2.4 2.6Undervoltage Lockout
70 125
V1.178 1.240 1.302Current-Limit-Amplifier Threshold
UNITSMIN TYP MAXPARAMETER
VIN = 3.0V mΩ
88 160
On-Resistance
IOUT = 500mA, VOUT > 1.6V A/A920 1080 1250IOUT to ISET Current Ratio
MAX893L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________ 3
ON = IN, VIN = VOUT = 5.5V
VIN = 5V, IOUT = 500mA
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
160
µs200
On-Resistance
Turn-On Time
V0.4
FAULT Logic Output Voltage Low
µA2.2Off-Supply Current
µA30
V3.0 5.5Operating Voltage
Quiescent Current
A/A865 1300IOUT to ISET Current Ratio
µA15Off-Switch Current
V2.0 2.9Undervoltage Lockout
125
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)
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.
VIN = 5V, IOUT = 500mA µs120Turn-Off Time
MAX893L
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
MAX893L 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
MAX893L toc05
TEMPERATURE (°C)
NORMALIZED RON
06080
1.2
1.0
0.7
1.3
1.1
0.9
IOUT = 1/2 ILIMIT
VIN = 5V
0
020 8060 140
IOUT/ISET RATIO
vs. ILIMIT
400
MAX89L 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
1.4
1.2
NORMALIZED OUTPUT CURRENT
vs. OUTPUT VOLTAGE
MAX893L toc07
OUTPUT VOLTAGE (V)
NORMALIZED OUTPUT CURRENT
01 234 56
ILIMIT = 1.2A
VIN = 5V
150
60
TURN-ON TIME
vs. TEMPERATURE
80
140
MAX893L toc08
TEMPERATURE (°C)
tON (µs)
120
100
70
130
110
90
ILOAD = ILIMIT
VIN = 3V
VIN = 5V
-40 -20 4020 10006080
ILOAD = ILIMIT
VIN = 5V
VIN = 3V
0
TURN-OFF TIME
vs. TEMPERATURE
2
6
MAX893L toc09
TEMPERATURE (°C)
tOFF (µs)
4
1
5
3
-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
MAX89L toc01
INPUT VOLTAGE (V)
01 234 56
ON = GND
IOUT = 0
QUIESCENT CURRENT (µA)
-40 -20 4020 100
QUIESCENT CURRENT
vs. TEMPERATURE
9
MAX89L toc02
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
06080
13
11
8
14
12
10
VIN = 3V
VIN = 5V
10
0.001
-40 -20 2006040 80 100
OFF-SUPPLY CURRENT
vs. TEMPERATURE
0.01
MAX893L toc03
TEMPERATURE (°C)
OFF-SUPPLY CURRENT (nA)
0.1
1
SWITCH TURN-OFF TIME
A
B
0V
0V
1µs/div
VIN = 5V, IOUT = ILIMIT/2
A: VON, 2V/div
B: VOUT, 2V/div
MAX893L toc14
SWITCH TURN-ON TIME
A
B
0V
0V
20µs/div
VIN = 5V, IOUT = ILIMIT/2
A: VON, 2V/div
B: VOUT, 2V/div
MAX893L toc13
CIN = 100µF, COUT = 0.1µF
A: VIN, 1V/div, AC-COUPLED
OUTPUT SHORT CIRCUIT
(FAST-LOOP RESPONSE)
A
C
B
IOUT 0V
2µs/div
VOUT 0V
B: IOUT, 2A/div
C: VOUT, 5V/div
MAX893L toc11
MAX893L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________
5
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX893L
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 +165°C.
FAULT
8
Set Current-Limit Input. A resistor from SET to ground sets the current limit for the switch.
RSET = 1.34 ·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 MAX893L 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 / 1080) 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 to the programmed current
limit (ILIMIT).
This switch is not bidirectional; therefore, the input volt-
age must be higher than the output voltage.
Setting the Current Limit
The MAX893L features internal current-limiting circuitry
with a maximum programmable value (IMAX) of 1.2A.
For best performance, set the current limit (ILIMIT)
between 0.2A ≤ILIMIT ≤1.2A. 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 / 1080
RSET = 1.24V / ISET = 1.34 ·103 / ILIMIT
where ILIMIT is the desired current limit.
Short-Circuit Protection
The MAX893L is a short-circuit protected switch. In the
event of an output short circuit or a current overload
condition, the current through the switch is limited by
the internal current-limiting error amplifier to 1.5 ·ILIMIT.
The short-circuit current is typically 1.8A for a pro-
grammed current limit of 1.2A. When the short-circuit
condition is removed, the replica error amplifier will set
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 supply
from the output. The current-limiting amplifier then slow-
ly turns the switch on with the output current limited to
1.5 ·ILIMIT. When the short-circuit condition is removed,
the current limit is set back to ILIMIT. See Output Short-
Circuit (Fast-Loop Response) and Output Overload
(Slow-Loop Response) in the
Typical Operating
Characteristics
.
MAX893L
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
MAX893L
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________ 7
Thermal Shutdown
The MAX893L features thermal shutdown. The switch
turns off when the junction temperature exceeds
+165°C. Once the device cools by 10°C, the switch
turns back on. If the fault condition is not removed, the
switch will cycle on and off, resulting in a pulsed out-
put.
Fault Indicator
The MAX893L provides a fault output (FAULT). This
open-drain output goes low when in current limit or
when the die temperature exceeds +165°C. A 100kΩ
pull-up resistor from FAULT to IN provides a logic-
control signal.
Fault Blanking
During start-up in USB applications, the MAX893L
charges the relatively large USB capacitance. This may
activate an unwanted fault signal if the charging current
exceeds the programmed current limit. To “blank out”
this start-up fault signal, add a simple lowpass RC
delay circuit as shown in Figure 3. This circuit provides
a 10ms delay.
Applications Information
Input Capacitor
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor no more
than 5mm 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 to prevent
inductive parasitics from pulling OUT negative during
turn-off.
Layout and Thermal-Dissipation
Considerations
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 to the device as possible
(no more than 5mm).
Under normal operating conditions, the package can
dissipate and channel heat away. Calculate the maxi-
mum power as follows:
P = (ILIMIT)2·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-shutdown 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: 340
MAX893L
SET
RSET
GND
Figure 2. Setting the Current Limit
MAX893L
C
0.1µF
BLANKED
SIGNAL
TO µP
R
100k
100k
IN VOUT
OUT
INPUT VOLTAGE
+5V
ON/OFF GND
RSET
FAULT SET
Figure 3. Fault-Blanking Circuit
MAX893L
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.
8
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