BQ24278 charge enable problem

challex

Other Parts Discussed in Thread: BQ24278

Recently i'v met a problem when I was designing the charging circuit using BQ24278. The problem is that the IC seems not working,I checked the input is OK.and I read many Subjects in this community. I wonder if it is the Problem of CD and /CE.?

over 9 years ago

0 Jeff F over 9 years ago

TI__Guru*** 149265 points

ISET cannot be left floating. A resistor to set the charge current is required.

0 challex over 9 years ago in reply to Jeff F

Prodigy 90 points

Well, it's not the problem of ISET,I'v tied a 200R resistor to it,but it doesn't change the problem.Will it be the problem of the grounding?

0 Jeff F over 9 years ago in reply to challex

TI__Guru*** 149265 points

1. the voltage between IN and GND pins is higher than the VINDPM threshold voltage

2. the voltage at TS is approx 1/2 VDRV

3. the voltage between BAT and GND pins is below 4.2V

4. the /CD and /CE pins are low

5. the load on SYS is not more than the input current can handle

Then the charger should be charging.

0 challex over 9 years ago in reply to Jeff F

Prodigy 90 points

well，I don't use the function of TS , and I pull TS to DRV , does the value of the resistor matters？ In this situation, the voltage at TS is approx 1/2 VDRV ?

0 Jeff F over 9 years ago in reply to challex

TI__Guru*** 149265 points

To disable TS function, V(TS) must be > 70% x VDRV. Using the resistor divider and 10kohm NTC, V(TS) ~= 50% x DRV at room temp.

If you are attaching your battery after the input power, try toggling the /CD pin.

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BQ24278 charge enable problem