Datasheet

Short-Circuit Protection
The MAX869L is a short-circuit-protected switch. In the
event of an output short circuit (V
OUT
≤ 1.6V typical),
the current through the switch is limited by the internal
current-limiting error amplifier to 1.4 x I
LIMIT
. When the
short-circuit condition is removed, the current-limit
amplifier sets the current limit back to I
LIMIT
.
For a high ∆V
DS
/∆t during an output short-circuit condi-
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
1.4 x I
LIMIT
. When the short-circuit condition is
removed, the current limit is set back to I
LIMIT
. Refer to the
Fast Current-Limit Response and Slow Current-Limit
Response graphs in the Typical Operating Characteristics .
Thermal Shutdown
The MAX869L features thermal shutdown. The switch
turns off when the junction temperature exceeds 135°C.
Once the device cools by 10°C, the switch turns back
on. If the fault condition is not removed, the switch
cycles on and off, resulting in a pulsed output.
Fault Indicator
The MAX869L provides a fault output (FAULT). This
open-drain output goes low when in current limit or
when the die temperature exceeds 135°C. A 100kΩ
pull-up resistor from FAULT to IN provides a logic-
control signal.
__________Applications Information
Input Capacitor
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor from IN to
GND. A 1µF ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce the voltage drop at the input.
Output Capacitor
Connect a 0.1µF capacitor from OUT to GND to prevent
inductive parasitics from pulling OUT below GND dur-
ing turn-off. USB applications require C
OUT
to be at
least 120µF. This larger output capacitance slows the
output rise and fall times, as shown in the Typical
Operating Characteristics , but does not adversely
affect the MAX869L’s turn-off response time.
Layout and Thermal-Dissipation
Considerations
To take full advantage of the switch-response time to
output short-circuit conditions, it is very important to
keep all traces as short as possible to reduce the effect
of undesirable parasitic inductance. Place input and
output capacitors as close as possible to the device
(less than 5mm).
MAX869L
2A, Current-Limited, High-Side
P-Channel Switch with Thermal Shutdown
_______________________________________________________________________________________ 7
MAX869L
P
P
P
R
SET
SET
OUT
GND
1.24V
N
FAULT
ON
ON
CURRENT-LIMIT
AMPLIFIER
REPLICA
AMPLIFIER
ON
HOT
IN
CONTROL
CIRCUITRY
Figure 1. Functional Diagram
MAX869L
SET
R
SET
GND
Figure 2. Setting the Current Limit