BQ76952: BQ76952EVM

Nadeem Yousaf

Prodigy 30 points

Part Number: BQ76952

We have developed our BMS board based on BQ76952. We have followed BQ76952EVM schematic.

BAT+ is 52 Volts.

On Q2 base it should be stable 6.0 volts but we are getting transients as in following figure

and at the emitter 5.5 vols (stable) but instead we are getting the following.

Therefore, there are transients at the LDO outputs REG1 and REG2. These are configured to produce 3.3 volts.

REG18 is giving stable 1.8 volts.

Please help to identify what is wrong with the circuit or with BQ76952.

A prompt response will be highly appreciated.

Regards!

over 1 year ago

0 Max Verboncoeur over 1 year ago

TI__Mastermind 25790 points

Hi Nadeem,

What is the collector voltage? It may not be high enough for the pre-regulator to properly regulate the voltage.

Regards,

Max Verboncoeur

0 Nadeem Yousaf over 1 year ago in reply to Max Verboncoeur

Prodigy 30 points

Collector Voltage is 52 Volts which is adequate for the pre-regulator to properly regulate.

0 Max Verboncoeur over 1 year ago in reply to Nadeem Yousaf

TI__Mastermind 25790 points

Hi Nadeem,

Looking at the schematic, RST_SHUT should have a pulldown to VSS on it, so that it doesn't float when the switch is open. We use a 10k pulldown on the EVM.

In addition to that, you can also try pressing the switch (S2) for less than a second to initiate a partial-reset. If the device is in soft-shutdown mode, then this would bring it back to normal mode.

Regards,

Max Verboncoeur

0 Nadeem Yousaf over 1 year ago in reply to Max Verboncoeur

Prodigy 30 points

Hi Max Verboncoeur,

I have follow the above instruction regarding partial reset, but still i am facing same problem.

In addition i have also connect the PACK PIN (42) and LD Pin(41) to BAT+ through series resistance 10K.

I need your assistance to resolve this problem .Thanks

Regards

0 Nadeem Yousaf over 1 year ago in reply to Nadeem Yousaf

Prodigy 30 points

Hi Max Verboncoeur,

I have remove the Transistor Q2 and apply external voltage of 5.5V on REGIN pin (36).I have analyse the same output on REG1 pin (35).

Picture of output is attached below.

0 Max Verboncoeur over 1 year ago in reply to Nadeem Yousaf

TI__Mastermind 25790 points

Hi Nadeem,

Is anything drawing current from REG1 and if there is anything, how much current is being drawn?

One thing that you could try is removing R20 and R21. TS2 should not need an external pullup, it has a weak internal pullup already. If there is even 1uA of leakage through the connected GPIO it could also pull down TS2.

Another thing to try is an A-B-A swap (video explaining the method) to see if the issue follows the IC or the board.

Regards,

Max Verboncoeur

Power management

Power management forum

BQ76952: BQ76952EVM