MAX893 [MAXIM]
1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown; 1.2A ，限流型，高边P沟道开关，带有热关断
| 型号： | MAX893 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1.2A, Current-Limited, High-Side P-Channel Switch with Thermal Shutdown |
| 文件： | 总8页 (文件大小：116K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1450; Rev 0; 7/99
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX893L
General Description
____________________________Features
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.
♦ +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
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.
13µA at V = 3.3V
IN
0.1µA with Switch Off
♦ Thermal Shutdown
♦ FAULT Indicator Output
♦ 0.07Ω On-Resistance
The MAX893L is available in an 8-pin SO package.
________________________Applications
Ordering Information
USB Ports
PART
TEMP. RANGE
PIN-PACKAGE
USB Hubs
MAX893LESA
-40°C to +85°C
8 SO
PCMCIA Slots
Access Bus Slots
Portable Equipment
Typical Operating Circuit
Pin Configuration
TOP VIEW
INPUT
IN
OUT
OUT
ON
OUTPUT
0.1µF*
IN
IN
IN
FAULT
8
1
2
3
4
MAX893L
100k
OUT
7
FAULT
GND
ON/OFF
MAX893L
OUT
SET
ON
6
5
1µF
SET
GND
R
SET
SO
*USB SPECIFICATIONS REQUIRE HIGHER CAPACITANCE.
________________________________________________________________ Maxim Integrated Products
1
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.
1.2A, 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
Operating Temperature Range
MAX893LESA ...................................................-40°C to +85°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
SET, OUT to GND ...................................... -0.3V to (V + 0.3V)
IN
Maximum Continuous Short-Circuit Switch Current .............2.0A
Continuous Power Dissipation (T = +70°C)
A
SO (derate 5.88mW/°C above +70°C) .........................471mW
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.
MAX893L
ELECTRICAL CHARACTERISTICS
(V = 3V, T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
IN
A
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
5.5
20
UNITS
V
Operating Voltage
Quiescent Current
Off-Supply Current
Off-Switch Current
Undervoltage Lockout
2.7
13
0.03
0.04
2.4
µA
µA
µA
V
V
= 5V, ON = GND, I
= 0
IN
OUT
1
ON = IN, V = V
= 5.5V
IN
OUT
15
ON = IN, V = 5.5V, V
= 0
IN
OUT
Rising edge, 1% hysteresis
2.0
2.6
125
160
1.302
V
V
V
= 4.5V
= 3.0V
70
IN
On-Resistance
mΩ
V
88
IN
Current-Limit-Amplifier Threshold
required to turn the switch off (Note 1)
1.178
1.240
SET
Maximum Programmable Continuous
Output Current Limit
1.2
A
Short-Circuit Current
1.8
A
A/A
V
I
to I
Current Ratio
I
= 500mA, V > 1.6V
OUT
920
1080
1250
0.8
OUT
SET
OUT
V
V
V
V
V
I
= 2.7V to 5.5V
= 2.7V to 3.6V
= 4.5V to 5.5V
= 5.5V
ON Input Voltage Low
ON Input Voltage High
ON Input Leakage Current
IN
IN
IN
2.0
2.4
V
0.01
0.5
1
3
µA
µA
V
ON
I
Bias Current
= 1.24V, I = 0; V = V
OUT IN OUT
SET
SET
= 1mA, V
= 1.4V
= 1V
SET
0.4
1
FAULT Logic Output Voltage Low
FAULT Logic Output High Leakage Current
Slow Current-Loop Response Time
Fast Current-Loop Response Time
SINK
SET
V
= 5.5V, V
0.05
5
µA
µs
µs
FAULT
20% current overdrive, V = 5V
IN
2
V
IN
V
IN
V
IN
= 5V, I
= 3V, I
= 5V, I
= 500mA
= 500mA
= 500mA
80
115
4
200
OUT
OUT
OUT
Turn-On Time
Turn-Off Time
µs
µs
2
2
_______________________________________________________________________________________
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX893L
ELECTRICAL CHARACTERISTICS
(V = 3V, T = -40°C to +85°C, unless otherwise noted.) (Note 2)
IN
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
5.5
UNITS
V
Operating Voltage
Quiescent Current
Off-Supply Current
Off-Switch Current
Undervoltage Lockout
3.0
30
µA
µA
µA
V
V
IN
= 5V, ON = GND, I
= 0
OUT
2.2
ON = IN, V = V
= 5.5V
IN
OUT
15
ON = IN, V = 5.5V, V
= 0
IN
OUT
Rising edge, 1% hysteresis
2.0
2.9
V
V
V
= 4.5V
= 3.0V
125
160
1.34
1300
0.4
IN
On-Resistance
mΩ
IN
Current-Limit-Amplifier Threshold
required to turn the switch off (Note 1)
1.14
865
V
A/A
V
SET
OUT
SINK
I
to I
Current Ratio
I
I
= 500mA, V
> 1.6V
OUT
OUT
SET
= 1mA, V
= 1.4V
FAULT Logic Output Voltage Low
Turn-On Time
SET
V
V
= 5V, I
= 5V, I
= 500mA
= 500mA
200
20
µs
µs
IN
OUT
Turn-Off Time
1
IN
OUT
Note 1: Tested with I
= 100mA and V
raised until V - V
≥ 0.8V.
OUT
SET
IN
OUT
Note 2: Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
__________________________________________Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
QUIESCENT CURRENT
vs. INPUT VOLTAGE
QUIESCENT CURRENT
vs. TEMPERATURE
OFF-SUPPLY CURRENT
vs. TEMPERATURE
14
10
1
14
V
= 5V
= 3V
IN
ON = GND
12
I
= 0
13
12
OUT
MAX893L
V
IN
10
8
11
0.1
6
10
9
4
0.01
2
0
8
0.001
0
1
2
3
4
5
6
-40 -20
0
20
40
60
80 100
-40 -20
0
20
40
60
80
100
INPUT VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
OFF-SWITCH CURRENT
vs. TEMPERATURE
I
/I RATIO
OUT SET
vs. I
LIMIT
1000
100
10
1.3
1400
I
V
= 1/2 I
= 5V
OUT
LIMIT
1.2
1.1
1.0
IN
1200
1000
800
0.9
600
1
0.8
0.7
0.6
400
200
0
0.1
0.01
-40 -20
0
20
40
60
80 100
-40 -20
0
20
40
60
80
100
0
20
40
60
80 100 120 140
(%)
TEMPERATURE (°C)
TEMPERATURE (°C)
I
LIMIT
TURN-ON TIME
vs. TEMPERATURE
NORMALIZED OUTPUT CURRENT
vs. OUTPUT VOLTAGE
TURN-OFF TIME
vs. TEMPERATURE
1.4
1.2
1.0
150
140
130
120
6
5
4
3
2
1
I
= I
LOAD LIMIT
I
= I
LOAD LIMIT
V
= 3V
I
= 1.2A
IN
LIMIT
V
= 5V
IN
0.8
0.6
110
100
90
V
= 3V
IN
0.4
0.2
0
V
IN
= 5V
80
70
60
V
IN
= 5V
0
-40 -20
0
20
40
60
80
100
0
1
2
3
4
5
6
-40 -20
0
20
40
60
80
100
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX893L
____________________________Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
OUTPUT OVERLOAD
(SLOW-LOOP RESPONSE)
OUTPUT SHORT CIRCUIT
(FAST-LOOP RESPONSE)
A
A
C
C
0V
V
0V
OUT
B
0A
B
I
0V
OUT
2µs/div
2µs/div
B: I , 1A/div
OUT
B: I , 2A/div
OUT
C
IN
= 100µF, C
= 0.1µF
C
IN
= 100µF, C
= 0.1µF
OUT
OUT
C: V , 5V/div
OUT
C: V , 5V/div
OUT
A: V , 1V/div, AC-COUPLED
IN
A: V , 1V/div, AC-COUPLED
IN
SWITCH TURN-ON TIME
SWITCH TURN-OFF TIME
A
A
0V
0V
B
B
0V
0V
20µs/div
1µs/div
V
= 5V, I
= I
IN
OUT LIMIT/2
V
= 5V, I
= I
IN
OUT LIMIT/2
A: V , 2V/div
B: V , 2V/div
ON
A: V , 2V/div
ON
B: V , 2V/div
OUT
OUT
_______________________________________________________________________________________
5
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
Pin Description
PIN
1, 2
3
NAME
IN
FUNCTION
Input. P-channel MOSFET source. Bypass IN with a 1µF capacitor to ground.
Active-Low Switch On Input. A logic low turns the switch on.
Ground
ON
4
GND
Set Current-Limit Input. A resistor from SET to ground sets the current limit for the switch.
= 1.34 · 103 / I
where I is the desired current limit in amperes.
5
6, 7
8
SET
OUT
R
SET
LIMIT,
LIMIT
MAX893L
Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1µF capacitor to ground.
Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature
exceeds +165°C.
FAULT
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
P
OUT
IN
MAX893L
limit, or 1.2A (I
), the current also increases through
MAX
FAULT
P
the replica switch (I
/ 1080) and through R
SET
OUT
(Figure 1). The current-limit error amplifier compares
the voltage across R to the internal 1.24V reference,
SET
N
REPLICA
AMPLIFIER
and regulates the current to the programmed current
limit (I ).
ON
LIMIT
This switch is not bidirectional; therefore, the input volt-
age must be higher than the output voltage.
P
SET
Setting the Current Limit
ON
CURRENT-LIMIT
AMPLIFIER
The MAX893L features internal current-limiting circuitry
with a maximum programmable value (I
) of 1.2A.
R
MAX
SET
1.24V
For best performance, set the current limit (I
)
LIMIT
between 0.2A ≤ I
≤ 1.2A. This current limit remains
LIMIT
in effect throughout the input supply-voltage range.
HOT
Program the current limit with a resistor (R
SET to ground (Figure 2) as follows:
) from
SET
GND
CONTROL
CIRCUITRY
ON
I
= I
/ 1080
SET
LIMIT
3
R
= 1.24V / I
= 1.34 · 10 / I
SET
SET LIMIT
where I
is the desired current limit.
LIMIT
Figure 1. Functional Diagram
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
For a high ∆V /∆t during an output short-circuit condi-
DS
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
the internal current-limiting error amplifier to 1.5 · I
.
LIMIT
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
1.5 · I
. When the short-circuit condition is removed,
LIMIT
the current limit is set back to I
. See Output Short-
LIMIT
Circuit (Fast-Loop Response) and Output Overload
(Slow-Loop Response) in the Typical Operating
Characteristics.
the current limit back to I
.
LIMIT
6
_______________________________________________________________________________________
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
MAX893L
INPUT VOLTAGE
IN
OUT
V
OUT
+5V
MAX893L
100k
SET
MAX893L
ON/OFF
GND
SET
R
SET
R
BLANKED
SIGNAL
TO µP
100k
FAULT
GND
C
0.1µF
R
SET
Figure 2. Setting the Current Limit
Figure 3. Fault-Blanking Circuit
Thermal Shutdown
Output Capacitor
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.
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).
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.
Under normal operating conditions, the package can
dissipate and channel heat away. Calculate the maxi-
mum power as follows:
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.
P = (I
2 · R
LIMIT)
ON
where R
is the on-resistance of the switch.
ON
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.
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.
Chip Information
TRANSISTOR COUNT: 340
_______________________________________________________________________________________
7
1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
________________________________________________________Package Information
MAX893L
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
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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