BQ24170 problem

shoujun sun

Other Parts Discussed in Thread: BQ24170

Hi TI,I design circuit to charge 3-cell Li-ion batterys refer to BQ24170 typical application,when test there are some problems as following:

1.When insert 13.5 adaptor,output voltage with no system load is right,13.5V.But when the load is connected ,the output voltage reduce to 1.2V.

2.The Vref is not 3.3V,3.6V.

3.Connect the battery to the board,the output volatge is right;

4.The led blink all the time.

thanx all!

over 11 years ago

0 Charles Mauney over 11 years ago

TI__Mastermind 31120 points

Would you please provide a schematic.

What are the specifications on the adapter you are using and what load are you applying?

0 shoujun sun over 11 years ago in reply to Charles Mauney

Prodigy 50 points

0 Charles Mauney over 11 years ago in reply to shoujun sun

TI__Mastermind 31120 points

The TS pin is biased so that it needs a 10k thermistor or it will be in cold fault.

Do you have a 10k thermistor connected or can use a 10k resistor from TS to GND to get out of cold fault.

What are the specifications on the adapter you are using and what load are you applying?

0 shoujun sun over 11 years ago in reply to Charles Mauney

Prodigy 50 points

Thank you Charles! The circuit is connected to a battery,there are a NTC in the battery.The problem is that the Vref

is not 3.3V,but 3.9V.I removed all the device but the power supply(AVCC),the Vref is still 3.9V.The Vref is simple LDO,I'm confused.Is the BQ24170 is false?i doubt.

0 Charles Mauney over 11 years ago in reply to shoujun sun

TI__Mastermind 31120 points

The VREF should be 3.3V. I see that the schematic shows a 1uF capacitor on that pin, which is good.

Can you put a scope probe on this pin and see that it is DC and not some oscillation.

I do not have an reason for the 3.9V at this time.

0 shoujun sun over 11 years ago in reply to Charles Mauney

Prodigy 50 points

Thank you very very much! I test the 3.3 with oscilloscope,It is DC voltage!

0 Charles Mauney over 11 years ago in reply to shoujun sun

TI__Mastermind 31120 points

I would assume the IC is bad. Have you tried a new IC?

0 shoujun sun over 11 years ago in reply to Charles Mauney

Prodigy 50 points

Hi,Charles,I'm back.I change the IC with a new one,but the Vref is 3.9V although .About PGND and AGND ,In the datasheet :

Route analog ground separately from power ground and use a single ground connection to tie charger power ground to charger analog ground. Just beneath the IC use analog ground copper pour but avoid power pins

to reduce inductive and capacitive noise coupling. Use the thermal pad as a single ground connection point

to connect analog ground and power ground together, or use a 0-Ω resistor to tie analog ground to power

ground. A star-connection under the thermal pad is highly recommended.

The PGND connect the AGND at the thermal pad, or through a 0R resistor.

But in the EVM ,the PGND and AGND is connect as :

The control stage and the power stage must be routed separately. At each layer, the signal ground and

the power ground are connected only at the thermal pad.

I seperate a AGND area on the PGND plane,and connect them with a 0R resistor,as

Is this connection cause the Vref error?

Thanks a lot!

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BQ24170 problem