Single rail power supplies are common in disk drive circuits, but sensor and control signals often require a voltage above ground potential. Using standard ADCs or DACs with these offset levels can reduce dynamic range due to unused codes or deadbands.
The AD7569/AD7669 is an 8-bit A/D and D/A system that allows operation with offset grounds for both the ADC and DAC independently. This configuration maintains full dynamic range by biasing the analog grounds (AGNDadc, AGNDdac) to match the signal offsets.
| Power Supply | single 5 V power supply |
|---|---|
| Signal Ranges | 0 to 1.25 V or 0 to 2.5 V |
| ADC Resolution | 8-bit |
| ADC Linearity Error Degradation | 0.2 LSBs at 0.5 V offset |
| DAC Linearity Error Degradation | less than 0.1 LSB at 0.5 V offset |
Yes, in most applications these independent ground connections would be externally connected together.
The pseudo grounds should be decoupled using 0.1 µF capacitors.