AD5555CRU Analog Devices Inc, AD5555CRU Datasheet - Page 14

• Manufacturer Part Number: AD5555CRU
• Description: IC DAC 14BIT DUAL SRL IN 16TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5555CRU

• Rohs Status: RoHS non-compliant
• Settling Time: 500ns
• Number Of Bits: 14
• Data Interface: Serial
• Number Of Converters: 2
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 55µW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP

AD5545/AD5555
DAC WITH PROGRAMMABLE INPUT
REFERENCE RANGE
Because high voltage references can be costly, users may
consider using one of the DACs, a digital potentiometer, and a
low voltage reference to form a single-channel DAC with a
programmable input reference range. This approach optimizes
the programmable range as well as facilitates future system
upgrades with just software changes. Figure 24 shows this
implementation. V
where:
V
V
D
N = number of bits of DAC
R
resistances and are given by
where D
(0 ≤ D
WB
REF
REF
A
= DAC A digital code in decimal
AB = reference voltage of V
and R
= external reference voltage
V
V
V
R
R
+5V
V
R
R
DD
REF
REF
REF
WB
WA
C
WA
WB
Figure 24. DAC with Programmable Input Reference Range
≤ 127).
AD5555
C
R
R
B
A
FB
AB
≈
= digital potentiometer digital code in decimal
FB
≈
WA
≈
U1A
U1B
B
A
A
A
128
128 −
D
128
GND
GND
are digital potentiometer 128-step programmable
I
I
=
OUT
C
OUT
128
V
D
R
A
B
−
B
REF
A
C
AB
D
D
REF
C
C
×
R
AB is in the feedback network, therefore,
⎛
⎜
⎜
⎝
AB
1
C1
C3
+
U2A
U2B
OP4177
OP4177
R
R
WB
WA
V+
V–
+15V
–15V
⎞
⎟
⎟
⎠
REF
–
POT
3
A and V
⎛
⎜
⎜
⎝
+15V
TEMP
4
–
V
GND
IN
V
2
REF_AB
U3
TRIM
V
AD7376
OUT
ADR03
V
O
REF
A
B
B
5
6
×
D
2
V
U4
N
A
REF
W
×
U2C
R
R
OP4177
C2
WA
B
WB
02918- 0- 024
2.2p
⎞
⎟
⎟
⎠
(10)
Rev. C | Page 14 of 20
(7)
(8)
(9)
V
REF_AB
By putting Equations 7 through 10 together, the following
results:
Table 9 shows a few examples of V
Table 9. V
D
0
32
32
64
64
96
96
The output of DAC B is, therefore,
where D
The accuracy of V
and feedback resistors and, therefore, a digital potentiometer is
used for U4 because of its inherent resistance
matching. The AD7376 is a 30 V or ±15 V, 128-step digital
potentiometer. If 15 V or ±7.5 V is adequate for the application,
a 256-step AD5260 digital potentiometer can be used instead.
C
V
V
OB
REF
B
=
is the DAC B digital code in decimal.
AB
REF
−
V
AB vs. D
=
REF
D
X
0
8192
0
8192
0
8192
V
REF
A
AB
REF
×
AB is affected by the matching of the input
D
2
B
N
B
and D
1
−
⎛
⎜
⎜
⎝
1
D
2
+
N
A
128
C
×
of the AD5555
D
128
−
REF
C
D
D
V
V
1.33 V
1.6 V
2 V
4 V
4 V
–8 V
−
AB of the 14-bit AD5555.
C
C
REF
REF
D
⎞
⎟
⎟
⎠
REF
REF
REF
C
AB
REF
REF
REF
(11)
(12)