Tool/software:
Hi,
I am using Big 25672 charger. I took the reference schematic from the Evolution board and I developed a custom board.but i am Using single grounding.
When I apply voltage to the board after assembly of the board it gives me good result.
When I increase it to maximum 20 volts suddenly the voltage drops near VABT AND SYS.
Even after I reduce the voltage it still doesn't work.
THANKS,
syam
Hi Jeff,
I am using the EVM board, but the output voltage fluctuates significantly, causing numerous issues in my circuit. How should you refer to the layout of the EVM board in such a case? Due to these fluctuations, I am experiencing considerable problems. The output signal of the EVM board is not stable. How can I take it as a reliable reference? This is causing me a lot of trouble.
Regards,
syam
Hi Syam,
As an example, below is the 798 with VBUS=12V, VREG=4.2V into a 2200uF capacitor on BAT (green) and a pulse load on SYS (pink). Battery charging is terminated because V(BAT)=4.2V and V(SYS) regulates to a fixed voltage slightly than VREG. The pulsing load results in V(SYS) being pulled down closer to battery voltage. If the input power was not enough to provide power to the system load, the pink would drop below the green trace to indicate that the battery was supplementing the load current.
My point here is that there will be some ripple on SYS. You can reduce but not eliminate the ripple on SYS by disabling PFM in REG0x12[4].
Regards,
Jeff
Hi Syam,
The EVM user's guide has pdf printouts of the layers. https://www.ti.com/tool/BQ25672EVM
Datasheet has simplified graphic below:
I have had customers use a 2 layer design successfully using the above concept but with inductor on the bottom under the IC.
Regards,
Jeff
