BQ24070: BQ24070

VAIBHAV BANSAL

Intellectual 420 points

Part Number: BQ24070
Other Parts Discussed in Thread: BQ24073, BQ24074

I am currently working on BQ24070RHLR single cell lithium ion charging IC in our application.

I am facing some problem. They are listed below.

1. Charge current won't exceed 450mA.

2. No indication of charge cutoff in IC.

3. Even battery is not connected still IC shows charging indication.

I am attached a screenshot of our circuit we are currently working on. Please review and suggest some changes if needed.

In brief we need charge current of 1.5A and we are using 5V 2-A AC adapter. We designed circuit for getting same output response.

over 6 years ago

0 Raheem over 6 years ago

TI__Mastermind 21590 points

Hello,
Can you measure the voltage on the mode pin and what is the value of R12?

0 VAIBHAV BANSAL over 6 years ago in reply to Raheem

Intellectual 420 points

Yes I had checked voltage across MODE Pin it s 5V.

R12 is 715 ohm as we need charge current up to 1.5 A.

I had checked voltages on other pins as well they all are as expected like

VREF = 3.36V

ISET = 5V

CE = 5V

TMR = 3.25V.

Still getting the charge current of 420mA max.

0 Raheem over 6 years ago in reply to VAIBHAV BANSAL

TI__Mastermind 21590 points

Hello,
Can you try to place a load on OUT and see if the device pulls more than 450mA from the input or if the device goes into supplement mode? Also check to ensure the input is not current limited and the voltage is not falling. After that, set ISET2 low and see if the charge current reduces.

0 VAIBHAV BANSAL over 6 years ago in reply to Raheem

Intellectual 420 points

I found the issues and charger IC is working but still Voltage on STAT1 & STAT2 pin not change even when charge current goes below 100 mA, when our charge current is 1.48 A.

0 Raheem over 6 years ago in reply to VAIBHAV BANSAL

TI__Mastermind 21590 points

What do you see on STAT1 and STAT2 when the charging is occurring and after charging is finished?

0 VAIBHAV BANSAL over 6 years ago in reply to Raheem

Intellectual 420 points

Voltages across STAT1 & STAT2 ;

when battery is not connected - 0.9 - 1.1 V & 3.6 V

when battery connected and IC in fast charging mode- 0.9 - 1.1 V & 3.6 V

when charge current drops 1/10th of fast charge current - 0.9 - 1.1 V & 3.6 V

These are the observation.

IC won't terminate charging, even when charge current drops to 0 A or some mA.

Battery voltage at 150 mA charge current is 4.179 V

0 Raheem over 6 years ago in reply to VAIBHAV BANSAL

TI__Mastermind 21590 points

Hello,
The device is not terminating because you have TMR connected to the VREF pin which disables the safety timer and termination. I'll suggest connecting a 100k ohm resistor to TMR to get the maximum safety timer duration

0 VAIBHAV BANSAL over 6 years ago in reply to Raheem

Intellectual 420 points

Can you explain the relation between charge termination and TMR pin.

As far as i know TMR pin will take care of safety timers such as fast charge timer, pre-charge timer, post-charge timer.

How is this related to TMR pin as IC should terminate charging when charge current goes 1/10th of fast charge current.

0 Raheem over 6 years ago in reply to VAIBHAV BANSAL

TI__Mastermind 21590 points

Vaibhav,
Charge termination occurs either when the charge current passes below the termination current or when the fast charge timer expires. If TMR is connected to VREF, this disabled the fast charge timer and termination. It's a feature that gives customers the option to not terminate charging in their application if they require that. I'll suggest connecting a 100k ohm resistor to TMR to get the maximum safety timer duration.

0 Raheem over 6 years ago in reply to Raheem

TI__Mastermind 21590 points

Vaibhav,
You can also take a look at the BQ24073 and BQ24074 which charge the batteries to 4.2V and regulate SYS voltage to 4.4V. Those devices don't disable termination when the fast charge timer is disabled

0 VAIBHAV BANSAL over 6 years ago in reply to Raheem

Intellectual 420 points

I understand what you are saying. We had done changes regarding that in our design.

Still i didn't get the relation between TMR and Charge Termination.

Rest i will mark this issues resolved when our design works.

PFA for the schematic file. If you find something odd, please let me know.

0 Raheem over 6 years ago in reply to VAIBHAV BANSAL

TI__Mastermind 21590 points

A couple f things i noticed about the schematic:
1. Will R27 R28 and R29 all be populated at the same time? If you only want to disable the fast charge safety timer, R28 and R29 are not needed
2. The device will never charge with the current resistors on the DPPM pin. The device will always enter DPPM mode since the current DPPM voltage setting is 15.8V.

0 VAIBHAV BANSAL over 6 years ago in reply to Raheem

Intellectual 420 points

I will take your suggestion in account and will get back to you if any issues found.

Thanks for your time.

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BQ24070: BQ24070