MAX869 Просмотр технического описания (PDF) - Maxim Integrated
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MAX869 Datasheet PDF : 8 Pages
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2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
A
0V
B
0V
C
0A
USB* CIRCUIT OUTPUT RISE TIME
A
0V
B
0V
C
0A
USB* CIRCUIT OUTPUT FALL TIME
D
0V
500µs/div
VIN = 5V, IOUT = 1A, CIN = 1µF, COUT = 120µF
A: VON, 5V/div
C: IOUT, 0.5A/div
B: VOUT, 2V/div
D: VFAULT, 2V/div
D
0V
500µs/div
VIN = 5V, IOUT = 1A, CIN = 1µF, COUT = 120µF
A: VON, 5V/div
C: IOUT, 0.5A/div
B: VOUT, 2V/div
D: VFAULT, 2V/div
*REFER TO TYPICAL OPERATING CIRCUIT
_____________________Pin Description
PIN
NAME
1, 4, 5,
12, 13, 16
IN
FUNCTION
Input, P-channel MOSFET source.
Bypass IN with a 1µF capacitor to
ground.
2, 3, 6,
11, 14, 15
OUT
7
ON
8
GND
9
SET
Switch output. P-channel MOSFET
drain. Bypass OUT with a 0.1µF
capacitor to GND.
Active-Low Switch-On Input. A logic
low turns the switch on.
Ground
Set Current-Limit Input. A resistor
from SET to ground sets the current
limit for the switch. RSET = 1,184 /
ILIMIT, where ILIMIT is the desired cur-
rent limit in amperes.
Fault-Indicator Output. This open-
drain output goes low when in cur-
10
FAULT
rent limit or when the die temperature
exceeds +135°C. FAULT remains low
for Turn-On Time + 50µs during start-
up.
_______________Detailed Description
The MAX869L P-channel MOSFET power switch limits
output current to a programmed level. When the output
current passes through the main switch, a smaller cur-
rent also passes through the replica switch (IOUT / 955)
and through RSET (Figure 1). When the voltage on RSET
exceeds the trip voltage of 1.24V, the current-limit error
amplifier regulates the output current to the pro-
grammed current limit, ILIMIT (400mA to 2.4A).
This switch is not bidirectional; therefore, the input volt-
age must be higher than the output voltage.
Setting the Current Limit
The MAX869L features internal current-limiting circuitry
with a maximum programmable value (IMAX) of 2.4A.
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 / 955
RSET = 1.24V / ISET = 1,184 / ILIMIT
where ILIMIT is the desired current limit.
6 _______________________________________________________________________________________
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