MAX893L Maxim, MAX893L Datasheet - Page 6

• Manufacturer Part Number: MAX893L
• Description: The MAX893L 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 MAX893L 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
and regulates the current to the programmed current
limit (I
This switch is not bidirectional; therefore, the input volt-
age must be higher than the output voltage.
The MAX893L features internal current-limiting circuitry
with a maximum programmable value (I
For best performance, set the current limit (I
between 0.2A ≤ I
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 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
the internal current-limiting error amplifier to 1.5 · I
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
the current limit back to I
6
PIN
1, 2
6, 7
_______________________________________________________________________________________
3
4
5
8
LIMIT
LIMIT
R
SET
FAULT
NAME
).
GND
OUT
SET
ON
IN
is the desired current limit.
= 1.24V / I
MAX
LIMIT
I
), the current also increases through
SET
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 +165°C.
SET
SET
OUT
Detailed Description
≤ 1.2A. This current limit remains
= I
Setting the Current Limit
SET
LIMIT
to the internal 1.24V reference,
Short-Circuit Protection
= 1.34
LIMIT
/ 1080) and through R
= 1.34 · 10
.
/ 1080
·
10
3
/ I
LIMIT,
3
/ I
MAX
LIMIT
where I
) of 1.2A.
SET
LIMIT
) from
LIMIT
LIMIT
SET
is the desired current limit in amperes.
)
.
For a high ∆V
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 · I
the current limit is set back to I
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 short-circuit condition is removed,
DS
/∆t during an output short-circuit condi-
CIRCUITRY
CONTROL
P
P
REPLICA
AMPLIFIER
HOT
Pin Description
ON
LIMIT
CURRENT-LIMIT
AMPLIFIER
. See Output Short-
ON
MAX893L
1.24V
P
SET
GND
OUT
R
SET