MAX891LEUA Maxim Integrated Products, MAX891LEUA Datasheet - Page 6

• Manufacturer Part Number: MAX891LEUA
• Description: Current Limit SW 1-IN 1-OUT 2.7V to 5.5V 0.5A 8-Pin uMAX
• Manufacturer: Maxim Integrated Products

Specifications of MAX891LEUA

• Package: 8uMAX
• Input Voltage: 2.7 to 5.5 V
• Maximum Output Current: 0.5(Typ) A
• Number Of Outputs: 1
• Operating Temperature: -40 to 85 °C

Current-Limited, High-Side
P-Channel Switches with Thermal Shutdown
The MAX891L/MAX892L P-channel MOSFET power
switches limit output current to a user-programmed
level. When the output current is increased beyond
the set current level, the current is also increased
through the replica switch (I
R
pares the voltage across R
erence and regulates the current back to the lesser of
the programmed current limit (I
current limit (I
These switches are not bidirectional; therefore, the
input voltage must be higher than the output voltage.
The MAX891L/MAX892L feature internal current-limit-
ing circuitry with maximum programmable values
(I
performance, set the current limit (I
0.2I
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 I
The MAX891L/MAX892L are short-circuit-protected
switches. In the event of an output short circuit or cur-
rent-overload condition, the current through the switch is
limited by the internal current-limiting error amplifier to
1.5 x I
replica error amplifier sets the current limit back to
I
6
______________________________________________________________Pin Description
_______________Detailed Description
LIMIT
SET
MAX
PIN
1, 2
7, 8
_______________________________________________________________________________________
3
4
5
6
MAX
OUT
.
) of 500mA and 250mA, respectively. For best
(Figure 1). The current-limit error amplifier com-
LIMIT
LIMIT
≤ I
to I
FAULT
NAME
GND
OUT
. When the fault condition is removed, the
SET
LIMIT
ON
SET
IN
is the desired current limit, and I
MAX
current ratio (965).
I
R
SET
).
≤ I
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. See Setting the
Current Limit section.
Fault-Indicator Output. This open-drain output goes low when in current limit or when the die temperature
exceeds +135°C.
Switch Output. P-channel MOSFET drain. Bypass OUT with a 0.1µF capacitor to ground.
MAX
= I
= 1.240 / I
Setting the Current Limit
LIMIT
. This current limit remains in
Short-Circuit Protection
SET
/ I
RATIO
to the internal 1.24V ref-
OUT
SET
LIMIT
/965) and through
) or the maximum
LIMIT
) between
SET
RATIO
) from
is
For a high
tion, the switch turns off and disconnects the input sup-
ply from the output. The current-limiting amplifier then
slowly turns the switch on with the output current limited
to 1.5 x I
current limit is set back to I
Limit Response graphs in the Typical Operating
Characteristics .
Figure 1. Functional Diagram
FAULT
FUNCTION
ON
IN
LIMIT
N
V
DS
. When the fault condition is removed, the
/ t during an output short-circuit condi-
CIRCUITRY
CONTROL
P
P
REPLICA
AMPLIFIER
LIMIT
HOT
ON
. Refer to the Current-
MAX891L
MAX892L
CURRENT-LIMIT
AMPLIFIER
ON
1.24V
P
SET
GND
OUT
R
SET