AP91352 Datasheet, PDF (8/12 Pages) Diodes Incorporated – SAS DISABLE plus 5V eFUSE WITH INTEGRATED ISOFET

AP91352
Application Note
Theory of Operation
The AP91352 is a self protected, resettable electronic fuse. It monitors the input and output voltage, the output current and the die temperature.
When the AP91352 is powered up it will ramp up the output voltage based on the fixed slew rate (see above electrical spec) and current will
begin to flow. The Overcurrent Protection, Overvoltage Clamp, Under Voltage Lockout and Thermal Protection are internally set.
Also, integrated reverse blocking MOSFET would prevent back-drive from an active load inadvertently causing undetermined behavior in the
application.
Overvoltage Clamping
The AP91352 monitor the input voltage and clamp output voltage once it exceeds 6.25V (MAX). This will allow for transient on the input for short
periods of time. If the input voltage stays above 6.25V (MAX) for extended times the voltage drop across the FET with the load current will
increase the die temperature and the thermal shutdown feature will protect the device and shut it down.
Under Voltage Lock Out
The input voltage of AP91352 is monitored by an UVLO circuit (under voltage lockout) if the input voltage drops below this threshold the output
transistor will be pulled into a high impedance state.
Enable/Fault
The AP91352 has a tri state EN/FAULT pin. It is used to turn on and off the device with high and low signals from a GPIO, but can also indicate a
thermal fault. When the EN/FAULT pin is pulled low the output is turned off, when the EN/FAULT pin is pulled high the output is turned on. Also,
the EN/FAULT pin would be internally pulled high after VCC reach UVLO. In the event of a thermal fault the EN/FAULT pin will be pulled low to
an intermediate voltage by an internal circuit. This can be used to chain up to 3 efuse together, like AP91352, NIS5132 (12V effuse), or NIS5135
(5V effuse) together that during a thermal shut down the linked devices turn off as well.
Due to this fault indication capability it should not be connected to any type of logic with an internal pull up device.
AP91352 connected to a 2^nd device will latch off until the EN/FAULT pin has been pulled to low and then allowed to go back up to a high signal,
or SAS pin has been toggled from High to Low or if the power has been cycled. Once the part starts up again it will go through the start-up ramp
determined by the internal circuit, 13ms (typ).
Symbol
UVLO
SASH
THSD
IREVERSE
SASO
SASL
–
Description
Under Voltage Lock Out
SAS Disable = 1
Thermal Shutdown
Reverse Current Protection
SAS Disable = Open
SAS Disable = 0
VCC > UVLO, No Fault
Enable/Fault
VL
VL
VM
VM
VH
VH
VH
eFuse State
Off
Off
Off
Off
On
On
On
Latching
No
N/A
Yes
(Note 8)
N/A
N/A
N/A
Table 1. EN/FAULT Signal Levels & Device Status
Thermal Protection
The AP91352 has an integrated temperature sensing circuit that protects the die in the event of over temperature. The trip point has been
intentionally set high at +150˚C (typ) to allow for increased trip times during high power transient events. The AP91352 will shut down current
flow to the output when the die temperature reaches +150°C (typ). The AP91352 will restart after the Enable pin has been toggled or the input
power has been cycled.
Even though the thermal trip point has been set high to allow for high current transients the circuit design should accomplish best thermal
performance with good thermal layout of the PCB. It is not recommended to operate AP91352 above +150°C over extended periods of time.
AP91352
Document number: DS38109 Rev. 1 - 2
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October 2015
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