AD7249 Analog Devices, AD7249 Datasheet - Page 8

• Manufacturer Part Number: AD7249
• Description: LC2MOS Dual 12-Bit Serial DACPORT
• Manufacturer: Analog Devices

Specifications of AD7249

• Resolution (bits): 12bit
• Dac Update Rate: 125kSPS
• Dac Settling Time: 7µs
• Max Pos Supply (v): +16.5V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Ser

AD7249
TRANSFER FUNCTION
The internal scaling resistors provided on the AD7249 allow
several output voltage ranges. The part can produce unipolar
output ranges of 0 V to +5 V or 0 V to +10 V and a bipolar
output range of ± 5 V. Connections for the various ranges are
outlined below. Since each DAC has its own R
DACs can be set up for different output ranges.
Unipolar (0 V to +10 V) Configuration
The first of the configurations provides an output voltage range
of 0 V to +10 V. This is achieved by connecting the output
offset resistor R
nary data format is selected by connecting BIN/COMP (Pin 7)
to DGND. In this configuration, the AD7249 can be operated
using either single or dual supplies. Note that the V
REFOUT
REFIN
SYNC
LDAC
SCLK
SDIN
CLR
V
SS
0V OR V
AD7249*
*ADDITIONAL PINS OMITTED FOR CLARITY.
OFSA
SS
, R
OFSB
DON'T
AGND
t
t
DB15
CARE
2
4
t
5
(Pin 3, 16) to AGND. Natural Bi-
V
DD
DON'T
CARE
DB14
DAC A
DAC B
12-BIT
12-BIT
t
1
V
DGND
DD
DON'T
CARE
DB13
DAC A
SELECT
DAC
DB12
A1
A2
=0
2R
2R
2R
2R
OFS
BIN/COMP
DB11
MSB
input the two
DD
R
R
V
0V TO 10V
V
0V TO 10V
OFSA
OFSB
OUTA
OUTB
supply is
LSB
DB0
t
3
t
10
DON'T
CARE
DB15
restricted to +15 V ± 10% for this range in order to maintain
sufficient amplifier headroom. Dual supplies may be used to
improve settling time and give increased current sink capability
for the amplifier. Figure 9 shows the connection diagram for
unipolar operation of the AD7249. Table I shows the digital
code vs. analog output for this configuration.
Unipolar (0 V to +5 V) Configuration
The 0 V to +5 V output voltage range is achieved by tying
R
can be operated using either single or dual supplies. The table
for output voltage versus digital code is as in Table I, with
2REFIN replaced by REFIN. Note, for this range, 1 LSB =
REFIN × (2
Input Data Word
XXXY 1111 1111 1111
XXXY 1000 0000 0001
XXXY 1000 0000 0000
XXXY 0111 1111 1111
XXXY 0000 0000 0001
XXXY 0000 0000 0000
X = Don’t Care.
Y = DAC Select Bit, 0 = DAC A, 1= DAC B.
Note: 1 LSB = 2REFIN/4096.
OFSA
DON'T
CARE
DB14
Table I. Unipolar Code Table (0 V to +10 V Range)
to V
MSB
DON'T
CARE
OUTA
DB13
–12
) = (REFIN/4096).
SELECT
or R
DAC B
DAC
DB12
=1
LSB
OFSB
DB10
MSB
to V
Analog Output, V
+2REFIN × (4095/4096)
+2REFIN × (2049/4096)
+2REFIN × (2048/4096) = +REFIN
+2REFIN × (2047/4096)
+2REFIN × (1/4096)
0 V
OUTB
. Once again, the AD7249
DB0
LSB
t
6
OUT
t
7
t
8
t
9