Power consumption on VDDA and VREFP on LPC845

[carstengroen]

Hello,

what is the current consumption on the LPC845 device for the Vdda pin, and also the Vrefp pins ?

The VDD (for the CPU itself) are well documented (and can be measured on the LPC845 MAX board, but the VDDA and VREFP are not easily accessible.

[xiangjun_rong]

Hi, Carsten,

I suppose that you can refer to the Table 14. Power consumption for individual analog and digital blocks in LPC84x.pdf(data sheet of LPC84x)

You can sum up the current of the ADC,two DAC and ACMP,  get the VDDA current. We have not Vrefp pin current spec.

Hope it can help you

BR

XiangJun Rong

[carstengroen]

Thanks,

I should have been more clear, what I need is the current used by the Vdda (and Vrefp) when device is in powerdown mode. According to the table above, it is 0 ? Is that correct, or is the "-" just because there is no data for it ? It would also be nice to know how it changes with regards to temperature.

[xiangjun_rong]

Hi, Carsten,

From Table 14. Power consumption for individual analog and digital blocks in data sheet of LPC84x.pdf, we see that the low power mode almost does not take effect on the power saving, because the ADC supply current almost is the same for the power-down and power-up modes. In other words, the power-down mode can save power only for digital circuit.

Hope it can help you

BR

Xiangjun Rong

[carstengroen]

Sorry, I still don't understand it.

Table 14 does not mention anything about powerup/down modes ?

it says:

"The supply current per peripheral is measured as the difference in supply current between
the peripheral block enabled and the peripheral block disabled in the SYSAHBCLKCFG
and PDRUNCFG (for analog blocks) registers. All other blocks are disabled in both
registers and no code accessing the peripheral is executed. Measured on a typical
sample at Tamb = 25 C."

It does only say something about the (digital) current at 2 clock frequencies, 12 and 30 MHz. It does not mention anything with regards to the power into Vdda (analog supply input) ?

Table 12 lists the operating conditions (voltages) for Vdd, Vdda and Vref. Table 13 says something about the Idd but NOT the IddA.

[xiangjun_rong]

Hi, Carsten,

It appears that the ADC current spec in Table 14 for LPC84x is incorrect.

This is the same table for LPC82x, you can see that the two ADC related bits in PDRUNCFG and ADC_CTRL registers can change the ADC supply current greatly.

i am checking with AE team if the ADC specs in data sheet of LPC84x is correct or not, maybe I misunderstand.

BR

Xiangjun Rong

[carstengroen]

Any update ?