BQ25672: doesn't work

micou ludovic

Part Number: BQ25672

Tool/software:

Hello,

I have a BQ25672 who doesn't work, it can communicate with the mcu but the voltage in the SYS pin is at 0.5 where it is at 7.5V in other pcb. the fault_status0 and fault_status_1 register are at 0x00. I don't have a input voltage read by the mcu but i have activate the ADC.

this is the register for charger_status read by the MCU:

Charger_status_0 = 0x0F

Charger_status_1 = 0x0A

Charger_status_2 = 0x40

Charger_status_3 = 0x00

Charger_status_4 = 0x10

I have this scope

SYS pin

pmid pin

SW1 pin

for a pcb who is good, sw1 is thi screen:

Best Regards,

Ludovic Micou

7 months ago

0 Jeff F 7 months ago

TI__Guru**** 165856 points

Hi Ludovic,

Can you provide the schematic? Have you tested with a BQ25672EVM? Is it possible that the SYS pin is accidentally shorted to GND? Can you use a DMM to measure SYS to GND resistance when not powered?

Regards,

Jeff

0 micou ludovic 7 months ago in reply to Jeff F

Expert 1215 points

Hi Jeff,

I have tested with a BQ25672EVM and it is operate. I have 5 BQ25672 in the board system that i have developped and the other is operate. in other board it is operate.

the impedance of this SYS pin is at 1.2Mohm but in the other BQ25672, it is at 13Mohm.

Charge batt1.pdf Charge Batt2.pdf Charge batt3.pdf Charge batt4.pdf Charge batt5.pdf

I have the problem with the part of Charge batt1.pdf

Best Regards,

Ludovic

0 Jeff F 7 months ago in reply to micou ludovic

TI__Guru**** 165856 points

Hi Ludovic,

SW2 is not connected properly.

Regards,

Jeff

0 micou ludovic 7 months ago in reply to Jeff F

Expert 1215 points

Hi Jeff,

Since I have 5 BQ25672 in the same board. I named the wires that must connect the inductance to SW2 in SWx with x corresponds to the battery that will be connected on it. then the wire SW1 is connected in SW2, in the charge batt3.pdf, this wire is named SW3.

Regards,

Ludovic

0 Jeff F 7 months ago in reply to Jeff F

TI__Guru**** 165856 points

HI Ludovic,

Ah. I see now. If SYS pin to GND is measuring low, there must a solder short somewhere. Also, what is the REGN capacitor voltage rating? It needs to be 10V-16V to account for dc bias derating.

Regards,

Jeff

0 micou ludovic 7 months ago in reply to Jeff F

Expert 1215 points

Hi Jeff,

I have 0V in REGN. I have 91ohms between REGN and GND.

Regards,

Ludovic

0 Jeff F 7 months ago in reply to micou ludovic

TI__Guru**** 165856 points

Hi Ludovic,

Then either there is a solder short from REGN to GND or the IC is damaged. What do VBUS to GND, SW1 to GND and VBUS to PMID resistances measure?

How high is your input voltage? If >15V, we strongly recommend an input RC snubber (2.2ohm+2.2uf) to damp ringing at input power hot plug. The IC abs max is 30V. Long cables = high inductance = inductive ringing up to 2X input DC voltage.

Regards,

Jeff

0 micou ludovic 7 months ago in reply to Jeff F

Expert 1215 points

Hi Jeff,

I have:

- VBUS to GND : 346ohm

- SW1 to GND : 4Mohm

- Vbus to PMID : 6Mohm

The input power voltage is 12V,

Regards,

Ludovic

+1 Jeff F 7 months ago in reply to micou ludovic

TI__Guru**** 165856 points

HI Ludovic,

The input side of the IC is damaged.

Regards,

Jeff

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BQ25672: doesn't work