AD AD8842ANZ 8-Bit Octal, 4-Quadrant Multiplying, CMOS TrimDAC

Manufactured bt Analog Devices - AD8842ANZ - DIL24 through hole package

DESCRIPTION

The AD8842 provides eight general purpose digitally controlled voltage adjustment devices. The TrimDAC® capability allows replacement of the mechanical trimmer function in new designs. The AD8842 is ideal for ac or dc gain control of up to 50 kHz bandwidth signals. The four-quadrant multiplying capability is useful for signal inversion and modulation often found in video vertical deflection circuitry.

Internally the AD8842 contains eight voltage output digital-toanalog converters, each with separate voltage inputs. A new current conveyor amplifier design performs the four-quadrant multiplying function with a single amplifier at the output of the current steering digital-to-analog converter. This approach offers an improved constant input resistance performance versus previous voltage switched DACs used in TrimDAC circuits, eliminating the need for additional input buffer amplifiers.

Each DAC has its own DAC register that holds its output state. These DAC registers are updated from an internal serial-toparallel shift register that is loaded from a standard 3-wire serial input digital interface. Twelve data bits make up the data word clocked into the serial input register. This data word is decoded where the first 4 bits determine the address of the DAC register to be loaded with the last 8 bits of data. A serial data output pin at the opposite end of the serial register allows simple daisy
chaining in multiple DAC applications without additional external decoding logic.

FEATURES

Low Cost
Replaces 8 Potentiometers
50 kHz 4-Quadrant Multiplying Bandwidth
Low Zero Output Error
Eight Individual Channels
3-Wire Serial Input
500 kHz Update Data Loading Rate
±3 V Output Swing
Midscale Preset, Zero Volts Out

APPLICATIONS

Automatic Adjustment
Trimmer Replacement
Vertical Deflection Amplitude Adjustment
Waveform Generation and Modulation

AD8842 Datasheet