BQ34Z100-G1: Power supply in REGIN pin

Hi Arun,

For sizing the power supply, although normal mode device operation has a low Iq, 10-20 mA may be required infrequently for flash updates.  When testing your circuit that you can write to the dataflash using bqStudio and ensure that REGIN does not droop.  The system is dynamic, please make sure to also account for the loading of REG25.  In addition, if operating LEDs from the preregulator, their current requirements will also need to be taken into account.

Power supply requirements for the bq34z100-G1 are simplified due to the presence of the internal LDO voltage regulation. The REGIN pin accepts any voltage level between 2.7 V and 4.5 V, which is optimum for a single-cell Li-Ion application. For higher battery voltage applications, a simple pre-regulator can be provided to power the bq34Z100-G1 and any optional LEDs. Decoupling the REGIN pin should be done with a 0.1-µF 10% ceramic X5R capacitor placed close to the device. While the pre-regulator circuit is not critical, special attention should be paid to its quiescent current and power dissipation. The input voltage should handle the maximum battery stack voltage. The output voltage can be centered within the 2.7-V to 4.5-V range as recommended for the REGIN pin. For high stack count applications, a commercially available LDO is often the best quality solution, but comes with a cost tradeoff.

For more information on power supply recommendations may be found in section 9 of the Datasheet: http://www.ti.com/lit/ds/symlink/bq34z100-g1.pdf

Since your input voltage is higher than 65 V, please refer to the High Cell Count and High Capacity Applications Application Note found here: http://www.ti.com/lit/slua760

The above App Note discusses how to scale parameters for high voltage/high current applications.

Sincerely,
Bryan Kahler