AWR1642: GPADC error increase on ES2.0 compared with ES1.0

Chris Meng

Part Number: AWR1642

Hi,

I tried to read external voltage by GPADC on xWR1642 ES2.0 and ES1.0 board. But I found GPADC error increases on ES2.0 compared with ES1.0.

I used the GPADC parameter in link_testcase_config.h in SDK 2.0 and SDK 1.2 for ES2.0 and ES1.0. I tried to adjust the parameter on ES2.0, but no effect.

Below are my test result. Would you pls kindly help to check if I miss anything?

	Detect by multimeter（V）	GPADC value	GPADC value to Voltage (V)	GPADC error (V)
xWR1642 ES2.0 EVM	1.7173	1023	1.8/1024*1023=1.798	0.0807
xWR1642 ES2.0 EVM	0	16	1.8/1024*16=0.0281	0.0281
xWR1642 ES1.0 EVM	1.711	975	1.8/1024*975=1.7134	0.0024
xWR1642 ES1.0 EVM	0	0	0	0

over 7 years ago

0 Cesar over 7 years ago

TI__Guru*** 148954 points

Hi,

We need to check with the design team

thank you
Cesar

0 Vivek Dham over 7 years ago in reply to Cesar

TI__Guru 58035 points

Hello Chris,
What is the source impedance you are using to feed the voltage? Is it a strong drive?
This seems to be a DC offset difference between two devices. This could vary slightly from device to device.

Regards,
Vivek

0 Chris Meng over 7 years ago in reply to Vivek Dham

TI__Mastermind 37756 points

Vivek,

I used GPADC to detect the VPP_1P7 on P7 of AWR1642 EVM (ES2.0 and ES1.0).

0 Vivek Dham over 7 years ago in reply to Chris Meng

TI__Guru 58035 points

Hello Chris,
Can you confirm if you are using the un-buffered mode and not the buffered mode? In buffered mode the max input voltage is only upto 1.4V.

Regards,
Vivek

0 Chris Meng over 7 years ago in reply to Vivek Dham

TI__Mastermind 37756 points

Vivek,

Yes. In my previous test on ES2.0, the GPADC is buffer enabled.

I tried to disable the buffer and got below result and it looks similar as ES1.0.

6-Aug	Buffer disabled
	Detect by multimeter（V）	GPADC value	GPADC value to Voltage (V)	GPADC error (V)
xWR1642 ES2.0 EVM	1.7176	980	1.8/1024*980=1.722656	0.0044
xWR1642 ES2.0 EVM	0	0	1.8/1024*0=0	0

Would you pls kindly advise what's the difference between buffer enabled and disabled for GPADC, excluding the max input voltage? Is there any advantage to use buffer enabled mode of GPADC?

0 Vivek Dham over 7 years ago in reply to Chris Meng

TI__Guru 58035 points

Hello Chris,
The buffered mode enables a buffer at the input of the ADC so that the source does not see the switching cap load of the ADC. Hence its useful if the source impedance of the voltage source is high. If you are directly connecting from the LDO output (low source impedance) then you use the unbuffered mode.

Regards,
Vivek

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AWR1642: GPADC error increase on ES2.0 compared with ES1.0