Bc127 vregen pull up


#1

Dear,

The EVM always powers up fine without pressing the Push Button that pulls up VREGEN pin to 3.3V. I designed a small board only to test BC127-HD and it also always powers up fine with VREGEN pin being floating only if 3.3V is applied to pin 30, 31, 32, 33, 34.

But, after I integrated BC127-HD into audio main board with VREGEN pin floating, BC127-HD powers up only by chance. Therefore, I pulled up VREGEN pin by 10k resistor and then, BC127-HD powers up always fine.

According to the ‘Power Supply Sequencing’ on Figure 5-1 in ‘Product Technical Specification’ document, VREGEN pin must go high 5ms after power is on and RST# pin must go low also 5ms after VREGEN pin goes high. The ‘Power Supply Sequencing’ is too difficult to realize only by simple HW and it also requires two dedicated GPIO if it is realized by MCU.

Question:
Is it OK to power up, if VREGEN pin is simply pulled up and does not follow the complex ‘Power Supply Sequencing’ strictly?

Meanwhile, the RST# pin does not seem to affect the power up results whether it is pulled up or not and how much capacitance is shunted to ground.

Thanks for all.