AD580

REV. A

–5–

Figure 8. Input Current vs. Input Voltage (Integral Loads)

THE AD580 AS A CURRENT LIMITER

The AD580 represents an excellent alternative to current lim-

iter diodes which require factory-selection to achieve a desired

current. This approach often results in temperature coefficients

of 1%/

°C. The AD580 approach is not limited to a specially

selected factory set current limit; it can be programmed from

1 mA to 10 mA with the insertion of a single external resistor.

The approximate temperature coefficient of current limit for

the AD580 used in this mode is 0.13%/

°C for I

0.01%/

°C for I

the high output impedance of the AD580 used as a current lim-

Figure 9. A Two-Component Precision Current Limiter

THE AD580 AS A LOW POWER, LOW VOLTAGE

PRECISION REFERENCE FOR DATA CONVERTERS

The AD580 has a number of features that make it ideally suited

for use with A/D and D/A data converters used in complex

microprocessor-based systems. The calibrated 2.500 volt output

minimizes user trim requirements and allows operation from a

single low voltage supply. Low power consumption (1 mA

quiescent current) is commensurate with that of CMOS-type de-

vices, while the low cost and small package complements the de-

creasing cost and size of the latest converters.

Figure 10 shows the AD580 used as a reference for the AD7542

12-bit CMOS DAC with complete microprocessor interface.

The AD580 and the AD7542 are specified to operate from a

single 5 volt supply; this eliminates the need to provide a +15

volt power supply for the sole purpose of operating a reference.

The AD7542 includes three 4-bit data registers, a 12-bit DAC

register, and address decoding logic; it may thus be interfaced

directly to a 4-, 8- or 16-bit data bus. Only 8 mA of quiescent

current from the single +5 volt supply is required to operate the

AD7542 which is packaged in a small 16-pin DIP. The AD544

output amplifier is also low power, requiring only 2.5 mA quies-

cent current. Its laser-trimmed offset voltage preserves the

±1/2 LSB linearity of the AD7542KN without user trims and it

typically settles to

±1/2 LSB in less than 3 µs. It will provide the

0 volt to –2.5 volt output swing from

±5 volt supplies.

Figure 10. Low Power, Low Voltage Reference for the

AD7542 Microprocessor-Compatible 12-Bit DAC