BQ24040: No output voltage set by charger ic to charge li-ion cell

Claus Janicher

Part Number: BQ24040

Hello,

I designed a circuit for lithium ion battery charging with the BQ24040. I tried to figure out why the battery does not charge but after some days of studying the data sheet and measuring the outputs I don't know how to solve this problem. I tested the circuit with an USB-Adapter power source, with and without the battery connected to the output but there were no changes. I tried the circuit with TS-PIN floating but there were no changes at all.

The circuit is shown below and my measured values from the ic-pins are the following:

IN = 5,2V (from USB Power source)

OUT = 3,53V (the actual cell voltage but without any kind of charging)

CHG = 2,7V

PG = 0,0V

ISET2 = 5,2V

ISET = 0,0V

PRE-TERM = 0,0V

The data sheet contains just the info that:

CHG (HIGH) = no charging

PG (LOW) = input voltage above Uvlow and Vout

I would appreciate any help or tips you can give. Thank you!

8 months ago

0 Bill Johns 8 months ago

TI__Guru 68596 points

Hi Claus

The Circuit looks OK do not see any problems.

Voltage readings show that the unit is in a no charge or shutdown state.

Float the TS pin should put unit in Power Supply Mode (TTDM) and you should see 4.2V on output.

Couple of things to try:

1.) Check for shorts on ISET or TS pin, both will shutdown unit.

2.) Also try grounding ISET2 as a test.

0 Claus Janicher 8 months ago in reply to Bill Johns

Prodigy 10 points

Hi Bill,

Thank you for your response. I tried both of your suggestions (with and without cell connected) but nothing changed.

0 Bill Johns 8 months ago in reply to Claus Janicher

TI__Guru 68596 points

Hi Claus

A couple of Application notes to check:

1.) https://www.ti.com/lit/pdf/slua949

2.) https://www.ti.com/lit/pdf/slua901

Do you have pcb plots that you can send for review?

How many of your boards are showing this problem?

0 Claus Janicher 8 months ago in reply to Bill Johns

Prodigy 10 points

Hello Bill,

Thank you for providing me these resources. I'll give them a check in the next days.

Currently there's only one BQ24040 soldered to one of my pcb boards. I'll try to solder another one tomorrow and keep you up to date.

Down below is a PCB plot. If you meant or need something else I'll provide it to you.

+1 Bill Johns 8 months ago in reply to Claus Janicher

TI__Guru 68596 points

Thanks for Layout, do not see any issues.

Do you have a 2ed or 3ed unit to try?

0 Claus Janicher 8 months ago in reply to Bill Johns

Prodigy 10 points

Alright that was probably my fault I should have stayed more patient and figure it out by myself. I tried my second PCB and I was very precise with putting soldering paste on + baking it in the reflow oven and the BQ24040 works now perfectly fine. I tried resoldering the first PCB with a heating-gun and in my opinion that destroyed the IC.

Output voltage is now fine between 4,0-4,2V and charged my cell to 4,184V so far. Only thing now is the charging current but I'll give it a check in the next days and then I would open a new topic.

Thank you for your tips and time. :)

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BQ24040: No output voltage set by charger ic to charge li-ion cell