Lpc55 power supply: DC-DC

[tyassin1]

Hi

Is it possible to supply an external voltage from a regulator to the input of VDD_PMU?

If you already have one in your design. Then you don’t use the DC-DC in the LPC55. 

thank you

[tyassin1]

Hi,
Thak you for the answer. Found a post soon after with the same question and answer

1. What is the switching frequency of the DC-DC converter?
2. Is it correct that LPC553x can be used without this DC-DC converter?

Br.
tyassin

[xiangjun_rong]

Hi,

The DC/DC converter switching frequency is in the range of from 15KHz to 500kHz, the frequency is dependent on the load for LPC55xx.

For the LPC553x/LPC55S3x, for the VDD_CORE pin, both the on-chip LDO and DC/DC converter are provided, user can select either LDO and DC/DC converter for the VDD_CORE power supply pin.

Hope it can help you

BR

XiangJun Rong

[xiangjun_rong · Accepted solution]

Hi,

For LPC55xx,the VDD_PMU power supply pin can power the core and peripherals, it's voltage is required to vary with the core frequency with software control, for example it can output 1.0V, 1.1V and 1.2V which corresponds to different core frequency. If you use on-chip DC/DC converter, it is easy to implement to adjust the voltage of the VDD_PMU power supply pin with different core frequency. If you use external regulator, it is almost impossible to adjust the voltage of VDD_PMU power supply pin.

In conclusion, it is strongly recommended to use on-chip DC/DC converter. Furthermore, we never have a test or verification to use external regulator for the VDD_PMU pin.

Hope it can help you

BR

XiangJun Rong