AD7943/AD7945/AD7948
TERMINOLOGY
Relative Accuracy
Output Capacitance
This is the capacitance from the I
OUT1
pin to AGND.
Output Voltage Settling Time
Relative Accuracy or endpoint linearity is a measure of the
maximum deviation from a straight line passing through the
endpoints of the DAC transfer function. It is measured after
adjusting for zero error and full-scale error and is normally
expressed in Least Significant Bits or as a percentage of full-
scale reading.
Differential Nonlinearity
This is the amount of time it takes for the output to settle to a
specified level for a full-scale input change. For these devices, it
is specified both with the AD843 as the output op amp in the
normal current mode and with the AD820 in the biased current
mode.
Digital to Analog Glitch Impulse
Differential nonlinearity is the difference between the measured
change and the ideal 1 LSB change between any two adjacent
codes. A specified differential nonlinearity of 1 LSB maximum
ensures monotonicity.
Gain Error
Gain Error is a measure of the output error between an ideal
DAC and the actual device output. It is measured with all 1s
in the DAC after offset error has been adjusted out and is ex-
pressed in Least Significant Bits. Gain error is adjustable to
zero with an external potentiometer.
Output Leakage Current
This is the amount of charge injected into the analog output
when the inputs change state. It is specified as the area of the
glitch in nV-s. It is measured with the reference input connected
to AGND and the digital inputs toggled between all 1s and all
0s. As with Settling Time, it is specified with both the AD817
and the AD820.
AC Feedthrough Error
This is the error due to capacitive feedthrough from the DAC
reference input to the DAC I
OUT1
terminal, when all 0s are
loaded in the DAC.
Digital Feedthrough
Output leakage current is current which flows in the DAC lad-
der switches when these are turned off. For the I
OUT1
terminal,
it can be measured by loading all 0s to the DAC and measuring
the I
OUT1
current. Minimum current will flow in the I
OUT2
line
when the DAC is loaded with all 1s.
When the device is not selected, high frequency logic activity on
the device digital inputs is capacitively coupled through the
device to show up as noise on the I
OUT1
pin and subsequently on
the op amp output. This noise is digital feedthrough.
PIN CONFIGURATIONS
DIP/SOP
SSOP
DIP/SOP/SSOP
DIP/SOP/SSOP
I
OUT1 1
I
OUT2
2
16
R
FB
15
V
REF
I
OUT1 1
I
OUT2 2
AGND
3
STB1
4
20
R
FB
19
V
REF
I
OUT1 1
AGND
2
DGND
3
DB11
4
20
R
FB
19
V
REF
I
OUT1 1
AGND
2
DGND
3
CSMSB
4
20
R
FB
19
V
REF
AGND
3
STB1
4
AD7943
14
V
DD
AD7943
18
V
DD
AD7945
18
V
DD
AD7948
18
V
DD
TOP VIEW
13
CLR
(Not to Scale)
12
DGND
LD1
5
11
STB4
10
STB3
9
TOP VIEW
17
CLR
(Not to Scale)
16
NC
NC
5
NC
6
15
NC
14
DGND
13
STB4
12
STB3
11
LD2
TOP VIEW
17
WR
(Not to Scale)
16
CS
DB10
5
DB9
6
DB8
7
DB7
8
DB6
9
DB5
10
15
DB0
14
DB1
13
DB2
12
DB3
11
DB4
TOP VIEW
17
WR
(Not to Scale)
16
CSLSB
DF/DOR
5
CTRL
6
DB7 (MSB)
7
DB6
8
DB5
9
DB4
10
15
LDAC
14
DB0 (LSB)
13
DB1
12
DB2
11
DB3
SRO
6
SRI
7
LD1
7
SRO
8
SRI
9
STB2
10
STB2
8
LD2
NC = NO CONNECT
–8–
REV. B
AD [ ANALOG DEVICES ]
