ADP3302: Input protection

Document created by analog-archivist Employee on Feb 23, 2016
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Does the ADP3302AR4/5 have reverse input protection, and what will it do to the
battery if it were inserted incorrectly.?  Is there any load dump protection? 
If suitable I would like to use two parts in a dual redundant configuration
with the outputs from one device connected to the outputs of the other device.
the grounds would be common but each device would be fed from seperate
batteries.  Under normal conditions one device would be powered and enabled,
the other device would be powered and the outputs disabled.  What is the
reverse current leakage for the part if it is in shutdown but the output is
forced high by the other device?  If only one device was powered would it back
feed through the unpowered device to it’s input? (i.e. body diode as in mosfet
pass elements).
Would the device be damged if configured in this way?  If both
parts were powered and both outputs enabled at the same time,
how would this affect current drain? and again what is the potential
for damaging the device in this condition.  Supply batteries will
be 6V lithium manganese 1300mAH, initial voltage can be as high
as 7.2V

 

1)Question: Does the ADP3302AR4/5 have reverse input protection?
Answer: ADP3302AR4/5 does not have reverse input protection but we do test and
guarantee for reverse leakage current on the pass transistor.  The test is done
by disabling the device, input is grounded and 12V is applied to the output and
we measure the leakage current of the pass transistor.  The leakage current is
in the order of 30-50nA under these conditions.
2)Question: What will it do to the battery if it were inserted incorrectly?
Answer: When the battery is inserted incorrectly, the ESD protection diode for
ADP3302AR4/5 will turn “on” and start draining current from the battery causing
current flow through the ESD protection diode.  If there is enough current
flows through the ESD diode, it will breakdown the ESD diode.  To prevent the
ESD diode from turning “on” in the event of the battery is inserted
incorrectly, we could place a diode between the battery and input pin.
3)Question: Is there any load dump protection?
Answer: I’m not really clear what your meant by this quesitons but I don’t
thinking our LDOs has load dump protection.  Most of our LDOs operated up to
12V maximum.
4)Question: If suitable I would like to use two parts in a dual redundant
configuration with the outputs from one device connected to the outputs of the
other device. the grounds would be common but each device would be fed from
separate batteries.  Under normal conditions one device would be powered and
enabled, the other device would be powered and the outputs disabled.  What is
the reverse current leakage for the part if it is in shutdown but the output is
forced high by the other device?
Answer:  The reverse leakage should be in the order of 30-50nA under these
conditions but no higher than 12uA at elevated temperature.
5)Question: If only one device was powered would it back feed through the
unpowered device to it’s input? (i.e. body diode as in mosfet pass elements). 
Would the device be damaged if configured in this way?
Answer: ADP3302AR4/5 pass transistor is a bipolar not a mosfet.  With a bipolar
as a pass element, you have a back-to-back diodes so you wouldn’t concern about
a current path back to it input.
6)Question: If both parts were powered and both outputs enabled at the same
time, how would this affect current drain? and again what is the potential for
damaging the device in this condition.  Supply batteries will be 6V lithium
manganese 1300mAH, initial voltage can be as high as 7.2V.
Answer: As long as the input voltage is higher than the output voltage, it
would not affect the collect current nor damage the part under these
conditions.

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