topic Re: LPC55S1x VBAT_DCDC rise time requirement in LPC Microcontrollers

LPC55S1x VBAT_DCDC rise time requirement

jackl_intercomp — Thu, 08 Dec 2022 14:13:29 GMT

Hello,

According to the LPC55S1x errata sheet, the rise time for the supply of the VBAT_DCDC pin should be at least 2.6 ms to guarantee startup in the worst case temperature. Is there a maximum slew rate for this requirement? For example, a voltage regulator we are considering using has the following startup timing:

The total rise time is well over the 2.6ms requirement. However, the jump from 0V to ~1.5V happens in about 0.375ms, which is a slew rate of 4V/ms. Will this cause a problem with the LPC55S1x?

Thanks.

Re: LPC55S1x VBAT_DCDC rise time requirement

Pavel_Hernandez — Tue, 13 Dec 2022 20:57:16 GMT

Hello,

I'm working on your case, please let me get more details about your question, and when I have more information, I will contact you.

Best regards,
Pavel

Re: LPC55S1x VBAT_DCDC rise time requirement

Pavel_Hernandez — Mon, 19 Dec 2022 17:29:59 GMT

Hello,

I review your case with my team unfortunately the regulator doesn't follow our datasheet. The ramp-up condition and slope should follow as mentioned below:

Best regards,
Pavel

Re: LPC55S1x VBAT_DCDC rise time requirement

jackl_intercomp — Mon, 19 Dec 2022 20:59:13 GMT

Ok, thank you for looking into this. We will take this regulator out of consideration then.