Sigma Delta Diff. Inputs, Voltage Swing

• Sigma Delta Diff. Inputs, Voltage Swing
  Posted by arrestedmechanics on 12 May, 2015 12:14
• I'm trying to use this sigma-delta ADC (MCP3911) for its quick settling time, and I'm a little confused about the input ratings.
  http://ww1.microchip.com/downloads/en/DeviceDoc/22286A.pdf
  
  The differential inputs are rated +/- 1V and are fed into a PGA before it gets to the modulator. Table 1-1 shows that the Analog Absolute Voltage on CH0+, CH0- can range from -1V to +1V, measured to AGND.
  
  So can this ADC actually measure a 2Vp-p signal centered around GND? I'm confused because it's only a single-supply chip, and the block diagram doesn't show any internal voltage inverter for the PGA.
  Do I supply -1V to REFIN-? Do I need to do the same for REFIN+, or can the ADC use the internal reference instead?
  
  Thanks for your help!
• #1 Reply
  Posted by bktemp on 12 May, 2015 12:24
• This ic seems to have an internal chargepump for generating a negative supply voltage. The datasheet mentions somewhere the the negative input range is only valid when a clock is applied, otherwise a higher input current flows when a negative input voltage is applied.
  
• #2 Reply
  Posted by arrestedmechanics on 12 May, 2015 19:17
• I sure hope you're right! I guess I'll give it a go 😁