BQ25618E: BQ25618E charge query

Star Xu

Part Number: BQ25618E
Other Parts Discussed in Thread: BQ25618

The customer test with BQ25618E, there are two problems:

1, When the IC enters CV mode, there will be a slight sudden change in the charging current at 50mA. What is the reason for this?

2, When the battery voltage is around 3.5V, when Vbus is inserted, the charging current will jump up and down briefly (within 1S). What is the reason for this?

The register setting as below:

Please help check it.

Thanks

Star

over 1 year ago

0 Michael Emanuel35 over 1 year ago

TI__Mastermind 35525 points

Hi Star,

1. Please provide more background information for these observations. What was the input voltage and battery voltage, was there a system load, how repeatable is this, was this seen on other device etc? Was the device in DPM? Please check the status when this happens.

2.The root of the observation is the BATFET turns off between linear mode and switching mode. The charger gets out of this scenario because the average current is positive. Please lower your PCB trace impedance and battery impedance to fix this issue. If possible lower VSYS_MIN to reduce the transition time to switch from linear mode to switch mode.

Regards,

Mike Emanuel

0 Star Xu over 1 year ago in reply to Michael Emanuel35

TI__Genius 9645 points

Hi Mike

Thanks for your help.

The VBus input voltage is 5V; the battery has entered the CV state, and the battery cut-off voltage is 4.45V; using the EVM for testing,

the EVM is used for testing without a load; the BQ25618 does not enter the DPM state; this phenomenon occurs every time.

Waiting for your reply.

Thanks

Star

0 Michael Emanuel35 over 1 year ago in reply to Star Xu

TI__Mastermind 35525 points

Hello Star,

Someone will get back to you by next Tuesday.

Regards,

Mike Emanuel

0 Michael Emanuel35 over 1 year ago in reply to Michael Emanuel35

TI__Mastermind 35525 points

Hi Star,

This phenomenon occurs in the transition from Continuous Conduction Mode (CCM) to Discontinuous Conduction Mode (DCM). It is expected.

Regards,

Mike Emanuel

0 switch over 1 year ago in reply to Michael Emanuel35

Genius 3140 points

Hi Michael，

Why would such a small current switch from CCM to DCM?

0 Michael Emanuel35 over 1 year ago in reply to switch

TI__Mastermind 35525 points

Hello,

Discontinuous conduction mode commonly occurs at light load operation when the inductor current reaches 0 A before the high side FET is turned on. It makes sense it would occur at low charge current. The charge current is sufficiently low to switch to DCM.

Regards,

Mike Emanuel

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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BQ25618E: BQ25618E charge query