MCP4921-E/SN Microchip Technology, MCP4921-E/SN Datasheet - Page 30

• Manufacturer Part Number: MCP4921-E/SN
• Description: IC DAC 12BIT SNGL W/SPI 8SOIC
• Manufacturer: Microchip Technology

Specifications of MCP4921-E/SN

• Number Of Converters: 1
• Package / Case: 8-SOIC (3.9mm Width)
• Settling Time: 4.5µs
• Number Of Bits: 12
• Data Interface: Serial, SPI™
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Resolution: 12 bit
• Interface Type: Serial (3-Wire, SPI, Microwire)
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2.7 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Package: 8SOIC N
• Architecture: Resistor-String
• Digital Interface Type: Serial (3-Wire, SPI, Microwire)
• Number Of Outputs Per Chip: 1
• Output Type: Voltage
• Full Scale Error: 1 %FSR
• Integral Nonlinearity Error: ±12 LSB
• Maximum Settling Time: 4.5(Typ) us
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power Dissipation (max): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MCP4901/4911/4921
6.5
Bipolar operation is achievable using the MCP4901/
4911/4921 family 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:
1.
2.
3.
DS22248A-page 30
If R
(a) Single Output DAC:
(b) Dual Output DAC:
Calculate the range: +2.05V – (-2.05V) = 4.1V.
Calculate the resolution needed:
4.1V/1 mV = 4100
Since 2
The amplifier gain (R
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:
1
V
V
V
= 20 k and R
OUT
IN+
O
1
–
-------- -
+ R
R
Bipolar Operation
=
R
1
2
=
=
V
DESIGN EXAMPLE: DESIGN A BIPOLAR
DAC USING EXAMPLE 6-3 WITH 12-BIT
MCP4912 OR MCP4922
12
2
=
IN+
), the V
V
------------------- -
R
V
= 4096, 12-bit resolution is desired.
OUT
3
–
------------ -
V
REF


2.05
+
REF
1
R
R
+
4

4
R
----- -
R
REF
2
G
=
REF
2
1
= 10 k, the gain will be 0.5
DIGITALLY-CONTROLLED BIPOLAR VOLTAGE SOURCE.



MCP4902
MCP4912
MCP4922
–
------------ -
MCP4911
MCP4921
MCP4901
D
------
2
–
2.05
4.1
source needs to be deter-
N
n
2
V
of 4.1V is used, solve for
/R
DD
1
), multiplied by V


R
----- -
R
2
1


R
----- -
R
2
1
=
1
-- -
2
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. Note that a pull-up to V
could be used, instead of R
desired.
4.
V
If R
OUT
Next, solve for R
4096, knowing that the output needs to be
+2.05V.
4
= 20 k, then R
3
and R
R
---------------------- -

R
3
R
3
illustrates a simple bipolar voltage source
R
4
+
V
4
4
1
R
REF
and R
4
shift the DAC's output to a selected

=
3
3
R
and R
2.05V
-----------------------------------------
2
= 10 k
 2010 Microchip Technology Inc.
1
allow the gain to be selected,
0.1 µF
V
1.5V
IN
4
+
+
4
by setting the DAC to
0.5V
REF
, if a higher offset is
V
V
CC
CC
REF
REF
+
–
instead of V
=
2
-- -
3
V
O
REF
SS