Differential ADC Anomaly on nRF9160 DK

Hi,

I'm trying to read differential ADC input with inputs configured as:

NRF_SAADC_INPUT_AIN1 (P0.014) -> POSITIVE

NRF_SAADC_INPUT_AIN2 (P0.015) -> NEGATIVE (differential mode)

I'm also using 4x oversampling, gain of 1, +-0.6V reference, 12-bit ADC and 5us acquisition time.

Unfortunately, I seem to be getting very poor results.

By grounding both inputs, I'm receiving an output value of ~350, which equates to around 103mV, which is too poor for my use case.

Any advise would be appreciated.

Regards,

Ben