LTC1289
PI FU CTIO S
CH0 – CH7 (Pins 1 – 8): Analog Inputs. The analog in-
puts must be free of noise with respect to AGND.
COM (Pin 9): Common. The common pin defines the zero
reference point for all single-ended inputs. It must be free
of noise and is usually tied to the analog ground plane.
DGND (Pin 10):Digital Ground. This is the ground for the
internal logic. Tie to the ground plane.
AGND (Pin 11): Analog Ground. AGND should be tied di-
rectly to the analog ground plane.
V– (Pin 12): Negative Supply. Tie V– to the most negative
potential in the circuit. (Ground in single supply applica-
tions.)
REF–, REF+ (Pins 13,14) Reference Inputs. The reference
inputs must be kept free of noise with respect to AGND.
CS (Pin 15): Chip Select Input. A logic low on this input
enables data transfer.
DOUT (Pin 16): Digital Data Output. The A/D conversion
result is shifted out of this output.
DIN (Pin 17): Digital Input. The A/D configuration word is
shifted into this input.
SCLK (Pin 18): Shift Clock. This clock synchronizes the
serial data transfer.
ACLK (Pin 19): A/D Conversion Clock. This clock con-
trols the A/D conversion process.
VCC (Pin 20): Positive Supply. This supply must be kept
free of noise and ripple by bypassing directly to the analog
ground plane.
BLOCK DIAGRAM
VCC 20
17
DIN
INPUT
SHIFT
REGISTER
CH0 1
2
CH1
3
CH2
CH3 4
CH4 5
6
CH5
CH6 7
CH7 8
9
COM
ANALOG
INPUT MUX
SAMPLE
AND
HOLD
COMP
12-BIT
CAPACITIVE
DAC
10
DGND
11
AGND
12
13
V–
REF–
14
REF+
18
SCLK
OUTPUT
SHIFT
REGISTER
16 DOUT
12-BIT
SAR
CONTROL
AND
TIMING
19
ACLK
15
CS
LTC1289 BD
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