PGA2500: default setting for DCEN 0dB and ZCEN

HI Ian,

1) On the case of 0dB, unity gain enable (Active High), you can set the 0dB pin low, and enable or disable unity gain with the serial interface. 

If you set in hardware the 0dB pin high, the PGA2500 gain will be forced to unity regardless of serial port settings, until you set 0dB pin low. This is shown on page 8 of the data sheet.

2) On the case of the zero crossing control input, ZCEN (pin 9), forcing the ZCEN input high enables the function. Zero crossing detection is used to force gain changes on zero crossings of the analog input signal. Forcing ZCEN low, disables the function, allowing immediate gain changes.  There is no serial port control for the ZCEN function on the PGA2500.

3) Regarding the DCEN, DC servo enable (Active low), normally this pin is set to low, where the PGA2500 analog output is monitored by the DC servo amplifier loop, minimizing the DC offset, with the DC bit on the serial port normally set low.  

The DC servo may be disabled by driving the DCEN input (pin 7) high or by setting the DC bit in the serial control word to 1.  If you set DCEN input high, the servo is disabled regardless of the serial control word.

Thank you and Regards,

Luis

thanks Luis!  all clear now.