7
LTC1821
I
OUT
(Pin 14): DAC Current Output. Normally tied through
a 22pF feedback capacitor in unipolar mode (15pF in
bipolar mode) to V
OUT
.
V
+
(Pin 15): Amplifier Positive Supply. Range is 4.5V to
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.
V
–
(Pin 20): Amplifier Negative Supply. Range is –4.5V
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.
V
CC
(Pin 2): Positive Supply Input. 4.5V ≤ V
CC
≥ 5.5V.
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.
R
COM
(Pin 9): Center Tap Point of the Two 4-Quadrant
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.
R
OFS
(Pin 11): Bipolar Offset Resistor. Typically swings
±10V, accepts up to ±15V. For 2-quadrant operation, tie
this pin to R
FB
and for 4-quadrant operation, tie this pin to
R1.
R
FB
(Pin12): Feedback Resistor. Normally connected to
V
OUT
. Typically swings ±10V. The voltage at this pin
swings 0 to V
REF
in unipolar mode and ±V
REF
in bipolar
mode.
V
OUT
(Pin 13): DAC Voltage Output. Normally connected
to R
FB
and to I
OUT
through a 22pF feedback capacitor in
unipolar mode (15pF in bipolar mode). Typically swings
±10V.
PIN FUNCTIONS
UUU