max5121beee Maxim Integrated Products, Inc., max5121beee Datasheet - Page 15

• Manufacturer Part Number: max5121beee
• Description: 3v/5v, 12-bit, Serial Voltage-output Dacs With Internal Reference
• Manufacturer: Maxim Integrated Products, Inc.

The settling time is the amount of time required from the
start of a transition until the DAC output settles to its new
output value within the converter’s specified accuracy.
Digital feedthrough is noise generated on the DAC’s
output when any digital input transitions. Proper board
layout and grounding will significantly reduce this
noise, but there will always be some feedthrough
caused by the DAC itself.
Figure 9 shows the MAX5120/MAX5121 setup for
unipolar, Rail-to-Rail
1.6384V/V. With its +2.5V internal reference, the
MAX5120 can generate a unipolar output range of 0V
to +4.095V. The MAX5121 produces a range of 0V to
+2.0475V with its on-board +1.25V reference. Table 5
lists example codes for unipolar output voltages. An off-
set to the output voltage can be achieved by simply
connecting the appropriate voltage to the OS pin, as
shown in Figure 10.
The MAX5120/MAX5121 can be configured for unity-
gain bipolar operation (OS = OUT) using the circuit
shown in Figure 11. The output voltage V
given by the following equation:
where NB is the numeric value of the DAC’s binary
input code, V
nal) precision reference, and G is the overall gain. The
application circuit in Figure 11 uses a low-cost opera-
tional amplifier (MAX4162) external to the MAX5120/
MAX5121 in a unity-gain configuration. This provides
an overall circuit gain of 2V/V. Table 6 lists example
codes for bipolar output voltages.
The MAX5120/MAX5121 DACs offer a clear pin (CLR)
that resets the output to a certain value, depending
upon how RSTVAL is set. RSTVAL = DGND sets the
output to 0, and RSTVAL = V
scale when CLR is pulled low.
The CLR pin has a minimum input resistance of 40k
series with a diode to the supply voltage (V
digital voltage is higher than the supply voltage for the
part, a small input current may flow, but this current will
be limited to (V
Note: Clearing the DAC will also cause the part to exit
software shutdown (PD = 0).
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Reset (RSTVAL) and Clear (
V
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
OUT
REF
CLR
= V
is the voltage of the internal (or exter-
______________________________________________________________________________________
REF
- V
DD
· [ {G · (NB / 4096)} - 1]
®
- 0.5V) / 40k .
operation with a gain of
DD
sets the output to mid-
Digital Feedthrough
Unipolar Output
CLR ) Functions
Bipolar Output
OUT
Settling Time
DD
is thereby
). If the
in
with Internal Reference
Figure 9. Unipolar Output Circuit (OS = AGND) Using Internal
(1.25V/2.5V) or External Reference. With external reference,
pull REFADJ to V
Figure 10. Circuit for Adding Offset to the DAC’s Output
Figure 11. Unity-Gain Bipolar Output Circuit Using Internal
(+1.25V/+2.5V) or External Reference. With external reference,
pull REFADJ to V
REF
DAC
MAX5120
MAX5121
GAIN = 1.638V/V
REF
REF
DD
DD
+5V/+3V
DAC
DAC
DGND
MAX5120
MAX5121
V
MAX5120
MAX5121
.
.
DD
REFADJ
0.6384R
AGND
AGND
R
AGND
+5V/+3V
+5V/+3V
V
V
OUT
DD
OS
DD
0.6384R
0.6384R
50k
OS
DGND
R
OS
DGND
R
V+
V-
50k
OUT
MAX4162
OUT
V
OS
V
OUT
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