AD569

REV. A

–7–

benefit is that, should a Zener diode fail (a short circuit would

be the most likely failure), the supply voltage decreases. This

differs from the situation where the diode is used as a series

regulator. In that case, a failure would place the unregulated

supply voltage on the AD569 terminal.

a. Zener Regulates Negative Supply

b. Diodes Regulate Both Supplies

c. Use of

±15 V and ±5 V Supplies

d. AD588 Produces References and Supply Voltages

Figure 7. Power Supply Options

ANALOG CIRCUIT CONNECTIONS

The AD569 is intended for use in applications where high reso-

lution and stability are critical. Designed as a multiplying D/A

converter, the AD569 may be used with a fixed dc reference or

set for reference voltages as discussed in the power supply range

section. Since the AD569 is a multiplying D/A converter, its

tal input word and the voltage at the reference terminal. The

nary value of the digital word applied to the converter using

offset-binary coding. Therefore, the output will range from

For applications where absolute accuracy is not critical, the

simple reference connection in Figure 8 can be used. Using only

the reference force inputs, this configuration maintains linearity

and 16-bit monotonicity, but introduces small, fixed offset and

gain errors. These errors are due to the voltage drops across re-

voltage, the gain and offset errors will range from 80 mV to

string to avoid degraded linearity due to uneven current densi-

ties at the string’s endpoints. Similarly, linearity would degrade

if the reference voltage were connected across the reference

sense terminals. Note that the resistance between the force and

sense terminals cannot be measured with an ohmmeter; the lay-

out of the thin-film resistor string adds approximately 4 k

Ω of

Figure 8. Simple Reference Connection

For those applications in which precision references and high

R1 to R256. This insures that any errors induced by currents

flowing through the resistances of the package pins, bond wires,

mized. Suitable amplifiers are the AD517, AD OP07, AD OP27,

or the dual amplifier, the AD712. Errors will arise, however, as

Ω). If

the bias currents produce such errors, resistance can be inserted

compensate for the errors.