MCP4922T-E/ST Microchip Technology, MCP4922T-E/ST Datasheet - Page 30

• Manufacturer Part Number: MCP4922T-E/ST
• Description: IC,D/A CONVERTER,DUAL,12-BIT,TSSOP,14PIN
• Manufacturer: Microchip Technology

Specifications of MCP4922T-E/ST

• Rohs Compliant: YES
• Settling Time: 4.5µs
• Number Of Bits: 12
• Data Interface: Serial, SPI™
• Number Of Converters: 2
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power Dissipation (max): -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: MCP4922T-E/ST; MCP4922T-E/STRTR; MCP4922T-E/STRTR; MCP4922T-E/STTR

MCP4902/4912/4922
6.5
Bipolar operation is achievable using the MCP4902/
4912/4922 family of devices by using an external
operational amplifier (op amp). This configuration is
desirable due to the wide variety and availability of op
amps. This allows a general purpose DAC, with its cost
and availability advantages, to meet almost any
desired output voltage range, power and noise
performance.
EXAMPLE 6-3:
6.5.1
An output step magnitude of 1 mV with an output range
of ±2.05V is desired for a particular application.
The following steps show the details:
Step 1: Calculate the range: +2.05V – (-2.05V) = 4.1V.
Step 2: Calculate the resolution needed:
Step 3:The amplifier gain (R
DS22250A-page 30
(a) Single Output DAC:
(b) Dual Output DAC:
V
V
V
OUT
IN+
O
4.1V/1 mV = 4100
desired.
must be equal to the desired minimum output
to achieve bipolar operation. Since any gain
can be realized by choosing resistor values
(R
mined first. If a V
the gain by setting the DAC to 0, knowing that
the output needs to be -2.05V. The equation
can be simplified to:
Since 2
Bipolar Operation
=
1
=
+R
=
V
DESIGN EXAMPLE: DESIGN A BIPOLAR
DAC USING EXAMPLE 6-3 WITH 12-BIT
MCP4922 OR MCP4921
IN+
V
------------------- -
R
2
V
OUT
3
), the V
REF


+
12
1
R
R
+
4

4
= 4096, 12-bit resolution is
R
----- -
R
G
2
1
DIGITALLY-CONTROLLED BIPOLAR VOLTAGE SOURCE


REF

MCP4902
MCP4912
MCP4922
MCP4911
MCP4921
MCP4901
D
------
2
–
REF
N
n
V
source needs to be deter-
DD
2
of 4.1V is used, solve for
/R


R
----- -
R
1
2
1
), multiplied by V


SPI
V
REF
3
REF
V
DD
D
G = Gain selection (1x or 2x)
N = DAC Bit Resolution
DAC
,
n
= Digital value of DAC (0-255) for MCP4901/MCP4902
= Digital value of DAC (0-1023) for MCP4911/MCP4912
= Digital value of DAC (0-4095) for MCP4921/MCP4922
Example 6-3
configuration. R
while R
offset. Note that R4 can be tied to V
if a higher offset is desired. Also note that a pull-up to
V
desired.
Step 4: Next, solve for R
V
If R
If R
REF
OUT
1
4
could be used instead of R
= 20 k and R
= 20 k, then R
3
–
-------- -
4096, knowing that the output needs to be
+2.05V.
R
R
and R
1
R
---------------------- -

2
R
3
R
=
3
illustrates a simple bipolar voltage source
R
4
+
V
–
------------ -
4
V
4
1
R
2.05
REF
REF
and R
4
shift the DAC’s output to a selected

=
2
=
3
= 10 k, the gain will be 0.5.
R
2.05V
-----------------------------------------
2
= 10 k
 2010 Microchip Technology Inc.
–
------------ -
3
1
allow the gain to be selected,
4.1
0.1 µF
2.05
and R
V
1.5V
IN
+
+
0.5V
REF
4
V
V
4
by setting the DAC to
CC
CC
, if a higher offset is
R
----- -
R
REF
2
REF
2
1
+
–
=
instead of V
=
1
-- -
2
2
-- -
3
V
O
SS
,