MX7847AR-T Maxim Integrated, MX7847AR-T Datasheet - Page 8

• Manufacturer Part Number: MX7847AR-T
• Description: Digital to Analog Converters - DAC
• Manufacturer: Maxim Integrated

Specifications of MX7847AR-T

• Number Of Converters: 2
• Number Of Dac Outputs: 2
• Resolution: 12 bit
• Interface Type: Parallel
• Settling Time: 4 us
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-24
• Minimum Operating Temperature: - 40 C
• Output Type: Voltage
• Voltage Reference: External

Figure 7 shows the MX7837/MX7847 connected for
binary operation. The offset-binary coding is shown in
Table 4. When V
4-quadrant multiplication. R1, R2, and R3 resistors
should be 0.01% ratio matched to maintain gain-error
specifications. On the MX7847, the R
resistor is internally connected to V
Table 4. Bipolar Code Table
Complete, Dual, 12-Bit
Multiplying DACs
Figure 6. Unipolar Binary Operation
8
Note : 1LSB
DAC Latch Contents
MSB
1111 1111 1111
1000 0000 0001
1000 0000 0000
0111 1111 1111
0000 0000 0000
_______________________________________________________________________________________
V
IN
* INTERNALLY CONNECTED ON MX7847
V
REFA
DGND
LSB
2048
V
Bipolar Operation (4-Quadrant
IN
DAC A
IN
is an AC signal, the circuit performs
AGNDA V
V
V
DD
DD
0V
V
V
V
V
IN
IN
IN
IN
SS
Analog Output, V
2047
2048
2048
2048
2048
2048
V
V
1
1
SS
SS
OUT
Multiplication)
MX7837
MX7847
.
V
R
OUTA
FBA
FB
V
*
*
IN
OUT
feedback
V
OUT
The use of an uninterrupted ground plane is strongly
recommended. AC or transient voltages between ana-
log and digital grounds (between AGNDA/AGNDB and
DGND) can inject noise into the analog circuitry.
Connect the MX7837/MX7847 AGNDs and DGND
directly to the ground plane or to a star ground to
ensure that they are at the same potential. In complex
systems with separate analog and digital ground
planes, connect two diodes (1N914 or equivalent) in
inverse parallel between the AGND and DGND pins.
To minimize noise, decouple the V
DGND using a 10µF capacitor in parallel with a 0.1µF
ceramic capacitor. Minimize capacitor lead lengths for
best noise rejection.
The MX7837/MX7847 are specified for operation with
V
amplifier requires 2.5V of headroom, so the reference
input should not come within 2.5V of V
maintain accuracy at full scale.
Figure 7. Bipolar Offset Binary Operation
__________Applications Information
DD
V
IN
/V
SS
V
DGND
REFA
= ±11.4V to ±16.5V. However, the output
DAC A
V
V
DD
DD
AGNDA
MX7837
MX7847
Power-Supply Decoupling
20k
R1
Operation with Reduced
Power-Supply Voltages
Ground Management
V
R
OUTA
V
FBA
V
SS
SS
*
10k
R3
DD
* INTERNALLY CONNECTED
DD
ON MX7847
and V
/V
MAX427
SS
20k
R2
SS
in order to
lines to
V
OUT