7

LTC1821

a 22pF feedback capacitor in unipolar mode (15pF in

16.5V.

AGNDS (Pin 16): Analog Ground Sense. Connect to

analog ground.

AGNDF (Pin 17): Analog Ground Force. Connect to

analog ground.

DNC (Pin 18, 19, 21): Connected internally. Do not

connect external circuitry to these pins.

to – 16.5V.

NC (Pin 22): No Connection.

LD (Pin 23): DAC Digital Input Load Control Input. When

LD is taken to a logic high, data is loaded from the input

register into the DAC register, updating the DAC output.

WR (Pin 24): DAC Digital Write Control Input. When WR

is taken to a logic low, data is written from the digital input

pins into the 16-bit wide input reigster.

D15 (Pins 25): MSB or Digital Input Data Bit 15.

D14 (Pin 26): Digital Input Data Bit 14.

D13 (Pin 27): Digital Input Data Bit 13.

D12 (Pin 28): Digital Input Data Bit 12.

D11 (Pin 29): Digital Input Data Bit 11.

D10 (Pin 30): Digital Input Data Bit 10.

D9 (Pin 31): Digital Input Data Bit 9.

D8 (Pin 32): Digital Input Data Bit 8.

D7 (Pin 33): Digital Input Data Bit 7.

D6 (Pin 34): Digital Input Data Bit 6.

D5 (Pin 35): Digital Input Data Bit 5.

D4 (Pin 36): Digital Input Data Bit 4.

DGND (Pin 1): Digital Ground. Connect to analog ground.

Requires a bypass capacitor to ground.

D3 (Pin 3): Digital Input Data Bit 3.

D2 (Pin 4): Digital Input Data Bit 2.

D1 (Pin 5): Digital Input Data Bit 1.

D0 (Pin 6): LSB or Digital Input Data Bit 0.

CLR (Pin 7): Digital Clear Control Function for the DAC.

When CLR is taken to a logic low, it sets the DAC output

and all internal registers to: zero code for the LTC1821 and

midscale code for the LTC1821-1.

REF (Pin 8): Reference Input and 4-Quadrant Resistor R2.

Typically

±10V, accepts up to ±15V. In 2-quadrant mode,

tie this pin to the external reference signal. In 4-quadrant

mode, this pin is driven by external inverting reference

amplifier.

Resistors R1 and R2. Normally tied to the inverting input

of an external amplifier in 4-quadrant operation. Other-

wise this pin is shorted to the REF pin. See Figures 1

and 2.

R1 (Pin 10): 4-Quadrant Resistor R1. In 2-quadrant

operation, short this pin to the REF pin. In 4-quadrant

mode, tie this pin to the external reference signal.

±10V, accepts up to ±15V. For 2-quadrant operation, tie

R1.

mode.

unipolar mode (15pF in bipolar mode). Typically swings

±10V.