_______________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 (I
OUT
/ 955)
and through R
SET
(Figure 1). When the voltage on R
SET
exceeds the trip voltage of 1.24V, the current-limit error
amplifier regulates the output current to the pro-
grammed current limit, I
LIMIT
(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 (I
MAX
) of 2.4A.
For best performance, set the current limit (I
LIMIT
)
between 0.2 I
MAX
≤ I
LIMIT
≤ I
MAX
. 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:
I
SET
= I
LIMIT
/ 955
R
SET
= 1.24V / I
SET
= 1,184 / I
LIMIT
where I
LIMIT
is the desired current limit.
MAX869L
2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
6 _______________________________________________________________________________________
_____________________Pin Description
PIN
Input, P-channel MOSFET source.
Bypass IN with a 1µF capacitor to
ground.
IN
1, 4, 5,
12, 13, 16
FUNCTIONNAME
Switch output. P-channel MOSFET
drain. Bypass OUT with a 0.1µF
capacitor to GND.
OUT
2, 3, 6,
11, 14, 15
GroundGND8
Active-Low Switch-On Input. A logic
low turns the switch on.
ON
7
Fault-Indicator Output. This open-
drain output goes low when in cur-
rent limit or when the die temperature
exceeds +135°C. FAULT remains low
for Turn-On Time + 50µs during start-
up.
FAULT
10
Set Current-Limit Input. A resistor
from SET to ground sets the current
limit for the switch. R
SET
= 1,184 /
I
LIMIT
, where I
LIMIT
is the desired cur-
rent limit in amperes.
SET9
