what is the input range for adc differential mode?

Hi i am using nrf52840 DK and

utilizing ble and adc functions

i configured my adc in my project as below

channel_config0.reference = NRF_SAADC_REFERENCE_INTERNAL; //Set internal reference of fixed 0.6 volts
channel_config0.gain = NRF_SAADC_GAIN1_6; 
channel_config0.acq_time = NRF_SAADC_ACQTIME_10US; 
channel_config0.mode =NRF_SAADC_MODE_DIFFERENTIAL;  (0V) internally.
channel_config0.pin_p = NRF_SAADC_INPUT_AIN0;
channel_config0.pin_n = NRF_SAADC_INPUT_AIN2;
channel_config0.resistor_p = NRF_SAADC_RESISTOR_DISABLED;
channel_config0.resistor_n = NRF_SAADC_RESISTOR_DISABLED; 
channel_config0.burst = NRF_SAADC_BURST_ENABLED;

1. from above configuration, i will get the difference between AIN0 and AIN2 right?

2. if so, what is the negative headroom for this configuration?

i have tested with gain=1/3 and 1Vpp sin wave  and

below -0.3V, my output showed some kind of distorted wave form( inaccurate )

i know when gain=1/6 for single ended, input range is 0~3.6V

does it mean that for differential mode -1.8V ~ 1.8V?

if not, what is the range?

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