This is an application note about AD9980, introducing the auto-offset function of AD9980
The document describes the auto-offset function of the AD9980, which calculates the required offset setting to yield a given output code during clamp. When enabled, registers 0x0B to 0x10 are used as target codes rather than offset values. The circuitry compares the output code after clamp to the target code and adjusts the offset accordingly.
The note details the changes to register definitions when auto-offset is enabled versus disabled, providing specific valid target code ranges for ground-clamped and midscale-clamped inputs. It also outlines recommended procedures for enabling auto-offset in both continuous update and hold modes, along with specific clamp timing requirements to ensure proper operation.
| Offset adjustment range | +63/-64 LSB |
|---|---|
| Auto-offset evaluation time | 16 to 40 data clock cycles |
Set register 0x1B, Bit 5 to 1.
It requires from 16 to 40 data clock cycles.