AD7226

REV. A

–11–

OFFSET ADJUST

Figure 21 shows how the AD7226 can be used to provide pro-

grammable input offset voltage adjustment for the AD544 op

amp. Each output of the AD7226 can be used to trim the input

offset voltage on one AD544. The 620 k

Ω resistor tied to +10 V

provides a fixed bias current to one offset node. For symmetrical

adjustment, this bias current should equal the current in the

other offset node with the half-full scale code (i.e., 10000000)

on the DAC. Changing the code on the DAC varies the bias

current and hence provides offset adjust for the AD544. For ex-

ample, the input offset voltage on the AD544J, which has a

maximum of

±2 mV, can be programmably trimmed to ±10 µV.

Figure 21. Offset Adjust for AD544

Microprocessor Interface

Figure 22. AD7226 to 8085A Interface

Figure 23. AD7226 to 6809 Interface

Figure 24. AD7226 to 6502 Interface

Figure 25. AD7226 to Z-80 Interface