BQ34Z100: REGIN oscillating

Ola Larsson1

Part Number: BQ34Z100

Tool/software:

Hello,

Is it normal for REGIN to oscillate? I see an oscillation with a period time of 425 ms on REGIN. It goes between voltage levels 3.5 to 4V and also before going up to 4V it has a short dip of 500 us down to 2V. I have the recommended mosfet setup with 10k and 2N7002 but with 5.1V zener instead of 5.6V. Is the zener voltage that critial?

7 days ago

0 Alan Frias 7 days ago

TI__Mastermind 25695 points

Hello,

This question has been assigned and will be reviewed when possible.

Thank you,
Alan

0 Diego 7 days ago in reply to Alan Frias

TI__Mastermind 25875 points

Hi,

The Zener diode should not cause any issues. Can you share your schematic?

Regin is the input for the LDO, are you suggesting that Regin is causing a voltage oscillation on your power rail?

Regards,

Diego

0 Ola Larsson1 3 days ago in reply to Diego

Prodigy 75 points

Hello,

Here is my schematic. I have tested with different resistors and capacitors on regin. There seems to be an oscilation at the regin pin regardless. I haven't actually mearusred if there is an oscillation on the other side of the FET. I have now tested with an LDO producing 3.3V and it is stable.

0 Diego 3 days ago in reply to Ola Larsson1

TI__Mastermind 25875 points

Hi,

Thanks for the schematic.

If you look on the EVM schematic there is a small circuit that is used to supply Regin, this affectively functions as an LDO. You will need a more stable power source (such as the LDO or other power rail) to supply Regin.

Regards,

Diego

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BQ34Z100: REGIN oscillating