Huawei D14 - DAH98AMBAD0 Rev.D - Laptop not Charging - Missing 137K on IADPT - Inductance Selection - BQ25713 Charging IC

[reessi]

Hello:

On the above laptop which wasn't charging I found only a tiny drop of water damage exactly on a few components by the BQ25713 Charging chip.. Bizarre how only that one 3mm square for it but it did..

I looked up the BQ25713 datasheet and replaced the 10K pull up resistor on the CHRG_OK line and now it charges!

But on the IADPT line which seams to be a resistor (137K) to tell the chip which Inductor is in use it is corroded also.. (Inductance Detection Through IADPT Pin - from datasheet).

So my question is what are the implications of leaving this resistor out as I don't have a spare.. I could order one I know but I would like to know what exactly the chip is doing with the knowledge of the knowing which inductor is there... In this case 137K = 2.2UH inductor.

It seams to work fine without this selection resistor..

On attached datasheet pages 7/26/73 for info on the IADPT pin..

Many thanks.

[mon2]

You will need to apply a pull-down resistor onto this leg (IADPT). You can try a 100k here.

[reessi]

Thankyou but I understand this, but I want to know what it is doing since it is charging fine without it! And I can easily order the 137K that is missing, I know the original was 137K as I measured it but the end cap was corroded off on one end so I couldn't solder it back in place..

[mon2]

The resistor is being used to define the inductor's inductance that is between the SW1 and SW2 pins. Best if you do apply a resistor as noted in the datasheet. Review the topside markings of the inductor on your board and select the resistor that is suitable from the shared chart. Select a 1% tolerant component. Digikey / Mouser / RS Electronics should offer these.

Being tiny parts, buy at least 10 or more and use nice tweezers for the placement. They will be dirt cheap (shipping will be more than the component cost).

[reessi]

Ok I'll replace it but if any one knows why the IC needs to know and what difference it makes not knowing then I would still like to know!

Many thanks.

[reessi]

Also what difference to the IC does the selection of the Inductor make when they are designing the circuit? It does not explain in the datasheet why you can pick different ones..

[reessi]

I ordered some of ebay, 25 pcs for £2. The laptop does appear to be fully working without it though, charged the battery normally and turned on etc..