MAX892L Maxim, MAX892L Datasheet - Page 7

• Manufacturer Part Number: MAX892L
• Description: The MAX891L/MAX892L smart, low-voltage, P-channel, MOSFET power switches are intended for high-side load-switching applications
• Manufacturer: Maxim

Figure 2. Setting the Current Limit
The MAX891L/MAX892L feature 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 short-circuit condition is not
removed, the switch will cycle on and off, resulting in a
pulsed output.
The MAX891L/MAX892L provide a fault output (FAULT).
This open-drain output goes low when in current limit or
when the die temperature exceeds +135°C. During
start-up, FAULT is low until the switch is fully on and no
over-current condition exists. A 100kΩ pull-up resistor
from FAULT to IN provides a logic-control signal.
To limit 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 voltage drop at the input.
__________Applications Information
P-Channel Switches with Thermal Shutdown
_______________________________________________________________________________________
MAX891L
MAX892L
GND
SET
Thermal Shutdown
Input Capacitor
Fault Indicator
R
SET
Current-Limited, High-Side
Connect a 0.1µF capacitor from OUT to GND. One
function of this capacitor is to prevent inductive para-
sitics from pulling OUT negative during turn-off.
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
(no more than 5mm).
Under normal operating conditions, the package dissi-
pates and channels heat away. Calculate maximum
power as follows:
where R
When the output is short circuited, voltage drop across
the switch equals the input supply. Hence, the power
dissipated across the switch increases, as does the die
temperature. If the fault condition is not removed, the
thermal-overload-protection circuitry turns the switch off
until the die temperature falls by 10°C. A ground plane
in contact with the device helps dissipate additional
heat.
TRANSISTOR COUNT: 396
SUBSTRATE CONNECTED TO GND
___________________Chip Information
ON
is the on-resistance of the switch.
Layout and Thermal-Dissipation
P = I
2
LIM
x R
ON
Output Capacitor
Consideration
7