●Product Details
●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-to-analog 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-to-parallel 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.
●The AD8842 consumes only 95 mW from ±5 V power supplies. For single 5 V supply applications consult the DAC-8841. The AD8842 is pin compatible with the 1 MHz multiplying band-width DAC8840. The AD8842 is available in 24-pin plastic DIP and surface mount SOL-24 packages.
●Applications
● Automatic Adjustment
● Trimmer Replacement
● Vertical Deflection Amplitude Adjustment
● Waveform Generation and Modulation
●### Features and Benefits
● 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
