AD7874
REV. C
–4–
TERMINOLOGY
ACQUISITION TIME
Acquisition Time is the time required for the output of the
track/hold amplifiers to reach their final values, within
±1/2
LSB, after the falling edge of INT (the point at which the track/
holds return to track mode). This includes switch delay time,
slewing time and settling time for a full-scale voltage change.
APERTURE DELAY
Aperture Delay is defined as the time required by the internal
switches to disconnect the hold capacitors from the inputs. This
produces an effective delay in sample timing. It is measured by
applying a step input and adjusting the CONVST input position
until the output code follows the step input change.
APERTURE DELAY MATCHING
Aperture Delay Matching is the maximum deviation in aperture
delays across the four on-chip track/hold amplifiers.
APERTURE JITTER
Aperture Jitter is the uncertainty in aperture delay caused by
internal noise and variation of switching thresholds with signal
level.
DROOP RATE
Droop Rate is the change in the held analog voltage resulting
from leakage currents.
CHANNEL-TO-CHANNEL ISOLATION
Channel-to-Channel Isolation is a measure of the level of
crosstalk between channels. It is measured by applying a full-
scale 1 kHz signal to the other three inputs. The figure given is
the worst case across all four channels.
SNR, THD, IMD
See DYNAMIC SPECIFICATIONS section.
PIN CONFIGURATIONS
DIP and SOIC
V
IN1
V
IN2
V
IN4
V
IN3
REF IN
AGND
DB0 (LSB)
V
DD
V
SS
REF OUT
CLK
DB1
V
DD
DB2
DB11 (MSB)
DB3
DB10
DB4
DB9
DB5
DB8
DB6
DGND
DB7
13
18
1
2
28
27
5
6
7
24
23
22
3
4
26
25
821
920
10
19
11
12
17
16
14
15
TOP VIEW
(Not to Scale)
AD7874
INT
CONVST
RD
CS
LCCC
V
DD
CLK
V
DD
V
IN4
V
IN2
V
IN1
DB9
DB8
DB6
DGND
DB7
REF OUT
REF IN
DB1
AGND
DB0 (LSB)
DB10
DB11 (MSB)
DB4
DB5
V
SS
V
IN3
DB3
DB2
AD7874
27
1
28
226
3
4
25
22
24
23
21
19
20
18
17
12 13
16
14 15
11
10
9
8
7
6
5
TOP VIEW
(Not to Scale)
CONVST
RD
CS
INT
