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AP9101CA - proper usage for Li-ion battery protection

Aussie Susan

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I have purchased a AP9101CA from Diodes Inc but I'm having problems with the 'auto-wake-up' part of its operation.
The basic operation is working well - once I trigger it into operation (by shorting out the 2 mosfets that separate the battery ground from the device ground - as per the data sheet) it will disconnect the device form the battery when the battery voltage does below the trigger point (2.5V for the version I'm using).
From what I read in the data sheet, the AP9101CA is the 'auto-wake-up' version (the AP9101C requires the manual restart I mentioned above) and it should re-trigger the power to the device when battery voltage gets above the 'over discharge release voltage' (2.9V for my device) but this is not happening - the device stays in sleep mode until it is manually re-triggered.
The only example of the use of the chip I can find is in the data sheet. therefore that s how I have it set up. on my breadboard.
Does anyone have any experience wth these chips and can provide me with a schematic that they have working and/or point out what is needed to properly re-trigger the device?
Susan
 

KlausST

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Hi,

Please show your complete schematic and wiring.

To debug: please measure the GATE voltage...to see whether it's the controller's fault or the MOSFET's fault.
Once I had the problem with a similar circuit where the MOSFET latched up somehow...and did not switch ON with proper gate voltage.

Try a different type of MOSFET.

Klaus
 

Aussie Susan

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I'm using the same circuit as in the data sheet on Page 2 (attached).
The MOSFETs are Vishay Si9945BDY (also attached).
The circuit is currently on a breadboard and I'm using a power supply instead of the battery. The load is a GPS receiver across the P+/P- points in the circuit.
I'll check the operation of the MOSFETs shortly and report back
Thanks for the assistance.
Susan
 

Attachments

  • AP9101C.pdf
    754.7 KB · Views: 2
  • Vishay SI9945BDY.pdf
    268.3 KB · Views: 1

Aussie Susan

Advanced Member level 4
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When the circuit is 'working', both the DO (discharge gate control) and CO (charge gate control) are high (actually they follow the battery voltage less a bit). As the battery voltage drops to the discharge trigger point (2.5V in my case), DO drops to 0V (relative to the battery earth) and CO drops to ~1.4V.
As the battery voltage increases, DO stays 0V and CO rises up until the battery voltage is 2.9V (just below the reset voltage) when it is ~1.75V. When th ebattery goes to 3.0V, CO drops slightly to ~1.6V and then continues to rise in step with the battery voltage (but about 1.4V below it).
If I then manually retrigger the chip (short the MOSFETS out) then both DO and CO jump up to the battery voltage and the current flows tot he device.
Does any of that make sense????
Susan
 

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