MAX890L Maxim, MAX890L Datasheet - Page 6

• Manufacturer Part Number: MAX890L
• Description: The MAX890L smart, low-voltage, P-channel, MOSFET power switch is intended for high-side load-switching applications
• Manufacturer: Maxim

1.2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
The MAX890L 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 (I
the replica switch (I
(Figure 1). The current-limit error amplifier compares
the voltage across R
ence and regulates the current back to the lesser of the
programmed limit (I
This switch is not bidirectional; therefore, the input volt-
age must be higher than the output voltage.
The MAX890L features internal current-limiting circuitry
with a maximum programmable value (I
For best performance, set the current limit (I
between 0.2 I
remains in effect throughout the input supply-voltage
range.
Program the current limit with a resistor (R
SET to ground (Figure 2) as follows:
where I
The MAX890L is a short-circuit-protected switch. In the
event of an output short circuit or current-overload con-
dition, the current through the switch is limited by the
internal current-limiting error amplifier to 1.5 x I
When the fault condition is removed, the replica error
amplifier sets the current limit back to I
6
PIN
1, 2
6, 7
_______________________________________________________________________________________
3
4
5
8
LIMIT
R
FAULT
NAME
SET
GND
OUT
SET
ON
IN
is the desired current limit.
MAX
MAX
= 1.24V / I
I
), the current also increases through
SET
LIMIT
≤ I
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
Set Current-Limit Input. A resistor from SET to ground sets the current limit for the switch.
R
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 +135°C.
SET
SET
Detailed Description
OUT
LIMIT
= I
Setting the Current Limit
) or 1.2A.
Short-Circuit Protection
8
= 1.38 x 10
LIMIT
to the internal +1.24V refer-
= 1.38 x 10
/1110) and through R
≤ I
/ 1110
MAX
3
/I
. This current limit
LIMIT,
3
LIMIT
/ I
LIMIT
MAX
where I
.
SET
) of 1.2A.
LIMIT
) from
LIMIT
LIMIT
SET
is the desired current limit in amperes.
)
.
For a high dV
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 x I
current limit is set back to I
Short-Circuit Fast-Loop Response and Output Overload
Slow-Loop Response in the Typical Operating
Characteristics .
Figure 1. Functional Diagram
FAULT
FUNCTION
ON
IN
LIMIT
N
. When the fault condition is removed, the
DS
/dt during an output short-circuit condi-
CIRCUITRY
CONTROL
P
P
REPLICA
AMPLIFIER
LIMIT
HOT
Pin Description
ON
. Refer to the Output
CURRENT-LIMIT
AMPLIFIER
ON
MAX890L
1.24V
P
SET
GND
OUT
R
SET