JAJSVE5 September 2024 DDS39RF12 , DDS39RFS12
PRODUCTION DATA
The DAC core analog output structure is shown in Figure 7-11 for one DAC channel. There is a differential termination resistance between the two current output pins, DACOUTx±. The current steering switch array connects to the output pins and steers current between the output pins based on the digital code. A constant DC current bias, IBIAS, draws current from both outputs regardless of the digital code. The IBIAS current is:
With a 3.6kΩ resistor from RBIAS+ to RBIAS-.
Examples of conversions from digital codes to currents on the IOUTx± outputs are given in Table 7-2. The currents shown in Table 7-2 include both the current steered portion and the bias currents on each leg.
DIGITAL CODE | 2'S COMPLEMENT | OFFSET BINARY | IDACOUTx+ | IDACOUTx– | IDACOUTx+ – IDACOUTx– |
---|---|---|---|---|---|
32767 | 0111 1111 1111 1111 | 1111 1111 1111 1111 | 0.9999847 × IFS + IBIAS | 0.0000153 × IFS + IBIAS | 0.9999694 × IFS |
16384 | 0100 0000 0000 0000 | 1100 0000 0000 0000 | ¾ × IFS + IBIAS | ¼ × IFS + IBIAS | ½ × IFS |
0 | 0000 0000 0000 0000 | 0000 0000 0000 0000 | ½ × IFS + IBIAS | ½ × IFS + IBIAS | 0 |
–16384 | 1100 0000 0000 0000 | 0100 0000 0000 0000 | ¼ × IFS + IBIAS | ¾ × IFS + IBIAS | –½ × IFS |
–32768 | 1000 0000 0000 0000 | 0000 0000 0000 0000 | IBIAS | IFS + IBIAS | –IFS |