LPC55xx: Specifications internal reference voltage

[janpieterderuit]

Hi,

from table 706 in the user manual (UM11126) I get that the ADC can measure a 1V reference voltage ("Bias_vref_1v from aux_bias module").

I would like to use it, but I can't find any specification for it in the datasheet (e.g. voltage tolerance and temperature dependency).

Wher can I find those specs?

Also from the SDK I get that bit 1 of the PDRUNCFG0 is used to disable/enable power to this bias voltage, however in table 291 of the user manual this bit is said to be reserved, and bit 19 should be used.

The SDK says that bit 19 is for LDOGPADC...

SDK says bit 15 is for GPADC, the user manual says this bit is also reserved.

All in all I'm a bit puzzled which bits I should use to get the ADC and reference voltage working.

Can someone explain how to use the reference voltage?

Thanks in advance. 

[xiangjun_rong]

Hi, Jan,

I have notified the AE team of updating the BIAS_VREF_1V part in the UM for LPC55xx family.

BR

Xiangjun Rong

[janpieterderuit]

OK, thanks

[xiangjun_rong]

Hi, Jan,

The bit 19 in PDRUNCFG0 for LPC55S69 can control the BIAS_VREF_1V. For accuracy of testing the 1V voltage reference,  user have to choose the two options for the ADC converter:

g_LpadcCommandConfigStruct.sampleTimeMode = kLPADC_SampleTimeADCK131;
g_LpadcCommandConfigStruct.hardwareAverageMode = kLPADC_HardwareAverageCount128;

As my colleague Jennie said that the voltage reference can reach up to 1.5% accuracy with above options

over working voltage and temperature range.

.

Hope it can help

BR

XiangJun Rong

[janpieterderuit]

Hi Jennie, XiangJun,

thanks for your response.

Will the datasheet/User Manual be updated with this info?

Jan Pieter

[xiangjun_rong]

Hi, Jan,

what the Um said is vague, I have asked the AE team, I will answer you after I get a feedback.

BR

Xiangjun Rong

[janpieterderuit]

Hi Xiangjun,

Do you have any update on this?

Thanks

[ZhangJennie · Accepted solution]

Jan,

BIAS_VREF_1V is 1.5% accuracy over working voltage and temperature range.

BR

Jun Zhang

[mse_videotec]

Hi!

Is it exactly 1.0V?

Many thanks

Mirco