MAXIM MAX895LESA

19-1153; Rev 0; 10/96
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
The MAX894L/MAX895L smart, dual, 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 currentlimiting circuitry protects the input supply against
overload. Thermal-overload protection limits power dissipation and junction temperature.
The MAX894L/MAX895L’s maximum current limits are
500mA and 250mA, respectively. The current limit
through the switches is programmed with resistors from
SET A/SET B to ground. When the switches are on, the
quiescent supply current is a low 16µA. When the
switches are off, the supply current decreases to 0.1µA.
The MAX894L/MAX895L are available in an 8-pin SO
package.
____________________________Features
♦ +2.7V to +5.5V Input Range
♦ Programmable Current Limits
♦ Low Supply Current:
16µA IQ at VIN = 3.3V
0.1µA with Switch Off
♦ Thermal Shutdown
______________Ordering Information
PART*
________________________Applications
PCMCIA Slots
Access Bus Slots
TEMP.
RANGE
MAX894LC/D
0°C to +70°C
MAX894LESA
-40°C to +85°C
MAX895LC/D
0°C to +70°C
MAX895LESA
-40°C to +85°C
PINPACKAGE
CURRENT
LIMIT
Dice**
500mA
8 SO
500mA
Dice**
250mA
8 SO
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.
Portable Equipment
__________Typical Operating Circuit
__________________Pin Configuration
TOP VIEW
OUTPUT A
OUT A
ONB
ON/OFF
0.1µF
OUTPUT B
IN
OUT B
MAX894L
MAX895L
0.1µF
SET A
INPUT
1µF
OUT B 2
SET A 3
SET B
RSET A
OUT A 1
RSET B
MAX894L
MAX895L
ONA 4
8
ONB
7
IN
6
SET B
5
GND
SO
ON/OFF
ONA
GND
________________________________________________________________ Maxim Integrated Products
1
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MAX894L/MAX895L
_______________General Description
MAX894L/MAX895L
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
ABSOLUTE MAXIMUM RATINGS
IN to GND ...................................................................-0.3V to 6V
ONA, ONB to GND .....................................................-0.3V to 6V
SET A, SET B, OUT A, OUT B to GND ........-0.3V to (VIN + 0.3V)
Maximum Continuous Switch Current
MAX894L ..........................................................................0.75A
MAX895L ........................................................................0.375A
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.88mW/°C above +70°C) .......................471mW
Operating Temperature Range
MAX89_LESA .................................................-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
CONDITION
Operating Voltage
V
30
µA
0.03
1
µA
0.04
3
µA
2.4
2.6
V
MAX894L
120
225
MAX895L
250
420
MAX894L
150
300
ONA = ONB = IN, VIN = VOUT A = VOUT B = 5.5V
Off-Switch Current
ONA = ONB = IN, VIN = 5.5V, VOUT A = VOUT B = 0
Undervoltage Lockout
Rising edge, 1% hysteresis
On-Resistance
VIN = 3.0V
Slow-Current-Loop Response Time
Turn-Off Time
500
1.302
250
945
1085
1270
MAX895L, IOUT = 125mA
910
1050
1235
0.8
VIN = 2.7V to 3.6V
2.0
VIN = 4.5V to 5.5V
2.4
V ONA = V ONB = 5.5V
0.01
1
0.5
3
VSET B = 1.24V, ONB = 0, ONA = VIN, IOUT B = 0
0.5
3
V
µA
µA
µs
2
µs
100
VIN = 3V, IOUT = 250mA (MAX894L), 125mA (MAX895L)
150
1.2
200
µs
20
µs
Note 1: Tested with IOUT = 50mA for the MAX894L and 25mA for the MAX895L, and VSET raised until VIN - VOUT ≥ 0.8V.
2
A/A
5
VIN = 5V, IOUT = 250mA (MAX894L), 125mA (MAX895L)
0.8
V
V
VSET A = 1.24V, ONA = 0, ONB = VIN, IOUT A = 0
20% current overdrive, VCC = 5V
mΩ
mA
MAX894L, IOUT = 250mA
Fast-Current-Loop Response Time
Turn-On Time
300
1.240
MAX895L
VIN = 2.7V to 5.5V
ISETA, ISETB Bias Current
1.178
500
ONA, ONB Input Low Voltage
ONA, ONB Input Leakage
MAX895L
MAX894L
VOUT = 1.6V to 2.8V
ONA, ONB Input High Voltage
2.0
VSET required to turn the switch off (Note 1)
IOUT to ISET Current Ratio
UNITS
5.5
Off-Supply Current
VIN = 4.5V
MAX
18
VIN = 5V, ONA = ONB = GND, IOUT A = IOUT B = 0
Maximum Output Current
TYP
2.7
Quiescent Current
Current-Limit-Amplifier Threshold
MIN
_______________________________________________________________________________________
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
MAX894L/MAX895L
ELECTRICAL CHARACTERISTICS (Note 2)
(VIN = 3V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
CONDITION
Operating Voltage
MIN
3.0
TYP
MAX
UNITS
5.5
V
Quiescent Current
VIN = 5V, ONA = ONB = GND, IOUT A = IOUT B = 0
50
µA
Off-Supply Current
ONA = ONB = IN, VIN = VOUT A = VOUT B = 5.5V
2.2
µA
Off-Switch Current
ONA = ONB = IN, VIN = 5.5V, VOUT A = VOUT B = 0
8
µA
Undervoltage Lockout
Rising edge, 1% hysteresis
2.9
V
VIN = 4.5V
On-Resistance
VIN = 3.0V
Current-Limit-Amplifier Threshold
250
MAX895L
420
MAX894L
300
MAX895L
VSET_ required to turn the switch off (Note 1)
IOUT to ISET Current Ratio
VSET = 1.24V,
VOUT = 1.6V to 2.8V
Turn-On Time
VIN = 5V
2.0
MAX894L
500
1.14
1.34
MAX894L, IOUT = 250mA
910
1360
MAX895L, IOUT = 125mA
880
1315
Turn-Off Time
mΩ
0.25
V
A/A
200
µs
20
µs
Note 2: Specifications 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
16
12
8
18
VIN = 5V
16
VIN = 3V
0.04
0.03
0.02
0.01
2
1
3
5
4
0
-40
6
-20
0
20
40
60
80
INPUT VOLTAGE (V)
TEMPERATURE (°C)
OFF-SWITCH CURRENT
vs. TEMPERATURE
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
MAX894 TOC-04
0.07
0.06
1.3
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
IOUT/ISET vs. ILIMIT
MAX894 TOC-05
0
MAX894 TOC-03
0.05
12
0
IOUT = 1/2 ILIMIT
1.2
1600
1400
1200
0.03
0.02
0.01
0
1000
1.0
0.9
800
600
0.8
400
0.7
200
0
0.6
0
20
40
60
80
-40
100
-20
0
20
40
60
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED OUTPUT CURRENT
vs. OUTPUT VOLTAGE
TURN-ON TIME
vs. TEMPERATURE
260
MAX894 TOC-06A
1.4
VIN = 5V
1.2
240
tON (µs)
0.6
ILOAD = ILIMIT
180
VIN = 3V
160
120
VIN = 5V
2
3
4
OUTPUT VOLTAGE (V)
5
6
100 120
140
7
ILOAD = ILIMIT
6
VIN = 5V
4
3
VIN = 3V
0
60
1
80
1
80
0
60
2
100
0.2
40
5
140
0.4
20
TURN-OFF TIME
vs. TEMPERATURE
200
0.8
0
0
100
ILIMIT (%)
220
ILIMIT
1.0
80
tOFF (µs)
-20
MAX894 TOC-07
-40
MAX894 TOC-08
0.04
1.1
IOUT/ISET RATIO
0.05
NORMALIZED RON
OFF-SWITCH CURRENT (µA)
20
0.06
14
4
4
22
0.07
MAX894 TOC-06
20
24
MAX894 TOC-02
24
QUIESCENT CURRENT (µA)
MAX894 TOC-01
ONA = ONB = GND
IOUT A = IOUT B = 0
QUIESCENT CURRENT (µA)
28
OFF-SUPPLY CURRENT
vs. TEMPERATURE
OFF-SUPPLY CURRENT (µA)
QUIESCENT CURRENT
vs. INPUT VOLTAGE
NORMALIZED OUTPUT CURRENT
MAX894L/MAX895L
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
-40
-20
0
20
40
60
TEMPERATURE (°C)
80
100
-40
-20
0
20
40
60
TEMPERATURE (°C)
_______________________________________________________________________________________
80
100
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
(Typical Operating Circuit, TA = +25°C, unless otherwise noted.)
CURRENT-LIMIT RESPONSE
(MAX894L, RL = 0.7Ω)
CURRENT-LIMIT RESPONSE
(MAX894L, RL = 1Ω)
A
5V
5V
A
B
B
C 0A
0A
0V
C 0V
MAX894/895/896 TOC-10
MAX894/895/896 TOC-9
1µs/div
2µs/div
CIN = 47µF, COUT = 0.1µF
A: VIN, 500mV/div, AC coupled
B: IOUT, 2A/div
C: VOUT, 5V/div
CIN = 47µF, COUT = 0.1µF
A: VIN, 500mV/div, AC coupled
LOAD-TRANSIENT RESPONSE
(MAX894L)
B: IOUT, 2A/div
C: VOUT, 5V/div
A
0A
B 0V
MAX494/495/496 TOC-13
2ms/div
VIN = 5V
A: IOUT = 0 to 500mA, 0.2A/div
B: VOUT RIPPLE, 200mV/div, AC COUPLED
SWITCH TURN-ON TIME
A
SWITCH TURN-OFF TIME
A
0V
B
B
0V
MAX894/895/896 TOC-11
20µs/div
VIN = 5V, IOUT = ILIMIT
A: VON, 2V/div
B: VOUT, 2V/div
2µs/div
MAX894/895/896 TOC-12
VIN = 5V, IOUT = ILIMIT
A: VON, 2V/div
B: VOUT, 2V/div
_______________________________________________________________________________________
5
MAX894L/MAX895L
____________________________Typical Operating Characteristics (continued)
MAX894L/MAX895L
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
1
OUT A
Switch A Output. P-channel MOSFET drain. Bypass OUT A with a 0.1µF capacitor to ground.
2
OUT B
Switch B Output. P-channel MOSFET drain. Bypass OUT B with a 0.1µF capacitor to ground.
3
SET A
Set Current-Limit Input. A resistor from SET A to ground sets the current limit for switch A. See Setting the
Current Limit section.
4
ONA
Active-Low Switch A On Input. A logic low turns switch A on.
5
GND
Ground
6
SET B
Set Current-Limit Input. A resistor from SET B to ground sets the current limit for switch B. See Setting the
Current Limit section.
7
IN
8
ONB
Input, Switches A and B. P-channel MOSFET source. Bypass IN with a 1µF capacitor to ground.
Active-Low Switch B On Input. A logic low turns switch B on.
P
IN
OUT A
OUT B
P
P
P
MAX894L
MAX895L
REPLICA
AMPLIFIER B
ON
ON
REPLICA
AMPLIFIER A
P
P
SET B
SET A
ON
RSET A
CURRENT-LIMIT
AMPLIFIER B
ON
CURRENT-LIMIT
AMPLIFIER A
RSET B
1.24V
1.24V
ONB
GND
ONA
CONTROL
CIRCUITRY
Figure 1. Functional Diagram
6
_______________________________________________________________________________________
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
The MAX894L/MAX895L 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 also increases through the
replica switch (IOUT/1050) (MAX895) 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.
Setting the Current Limit
The MAX894L/MAX895L feature internal current-limiting
circuitry with maximum programmable values (IMAX) of
500mA, and 250mA, respectively. For best performance, set the current limit (ILIMIT) between 0.2IMAX ≤
I LIMIT ≤ I MAX . This current limit remains in effect
throughout the input supply-voltage range.
Program the current limit with a resistor (RSET_) connected from SET_ to ground (Figure 2) as follows:
ISET = ILIMIT / IRATIO
RSET = 1.24V / ISET = (1.24V x IRATIO) / ILIMIT
where ILIMIT is the desired current limit for either switch
and IRATIO is the IOUT to ISET current ratio (1085mA for
the MAX894L and 1050mA for the MAX895L.
Short-Circuit Protection
The MAX894L/MAX895L are short-circuit-protected
switches. In the event of an output short circuit or current-overload condition, the current through either 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 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 ISET. When the fault condition is removed, the current
limit is set back to ILIMIT. Refer to Output Short-Circuit
Fast-Loop Response and Output Short-Circuit Slow-Loop
Response in the Typical Operating Characteristics.
Thermal Shutdown
The MAX894L/MAX895L 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 cycles on and off, resulting in a
pulsed output.
SET
MAX894L
MAX895L
RSET
GND
Figure 2. Setting the Current Limit
__________Applications Information
Input Capacitor
To limit input voltage drop during momentary output
short-circuit conditions, place 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. This
capacitor prevents inductive parasitics 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, reducing 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 = I2LIMITA x R ONA + I2LIMITB x R ONB
where R ONA and R ONB are the on-resistances of
switches A and B, respectively.
When one or both outputs are 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 helps
to further dissipate heat.
_______________________________________________________________________________________
7
MAX894L/MAX895L
_______________Detailed Description
MAX894L/MAX895L
Dual, Current-Limited, High-Side P-Channel
Switches with Thermal Shutdown
___________________Chip Information
TRANSISTOR COUNT: 453
SUBSTRATE CONNECTED TO GND.
__________________________________________________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.
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
© 1996 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.