MCP4821-E/P Microchip Technology, MCP4821-E/P Datasheet - Page 28

• Manufacturer Part Number: MCP4821-E/P
• Description: IC DAC 12BIT W/SPI 8DIP
• Manufacturer: Microchip Technology

Specifications of MCP4821-E/P

• Number Of Converters: 1
• Package / Case: 8-DIP (0.300", 7.62mm)
• 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: Through Hole
• 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: Through Hole
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power Dissipation (max): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MCP4801/4811/4821
6.6
Bipolar
MCP4801/4811/4821 family of devices by utilizing an
external
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:
6.6.1
An output step magnitude of 1 mV, with an output range
of ±2.05V, is desired for a particular application.
Step 1: Calculate the range: +2.05V – (-2.05V) = 4.1V.
Step 2: Calculate the resolution needed:
Step 3: The amplifier gain (R
DS22244B-page 28
(a) Single Output DAC:
(b) Dual Output DAC:
4.1V/1 mV = 4100
Since 2
scale V
minimum output to achieve bipolar operation.
Since any gain can be realized by choosing
resistor values (R
selected first. If a V
solve for the amplifier’s gain by setting the DAC to
0, knowing that the output needs to be -2.05V.
V OUT
V
Bipolar Operation
IN+
operation
V
operational
DESIGN EXAMPLE: DESIGN A
BIPOLAR DAC USING
WITH 12-BIT MCP4821 OR
MCP4822
OUT
O
12
=
=
=
= 4096, 12-bit resolution is desired.
(4.096V), must be equal to the desired
2.048 G
V
------------------- -
R
V
MCP4801
MCP4811
MCP4821
MCP4802
MCP4812
MCP4822
OUT
IN+
3
+


R
R
DIGITALLY-CONTROLLED BIPOLAR VOLTAGE SOURCE
1
1

is
+R
4
4
amplifier
+
REF

R
----- -
R
2
D
------
2
), the V
2
1
achievable
N
n


of 4.096V is used (G=2),
2
–
/R
V
DD
1
), multiplied by full-
REF
(op


R
----- -
R
EXAMPLE 6-3
2
1


value must be
SPI
amp).
using
3-wire
This
V
the
D
G
N
DD
DAC
n
=
=
=
=
=
Gain selection (1x or 2x)
Digital value of DAC (0-255) for MCP4801/MCP4802
Digital value of DAC (0-1023) for MCP4811/MCP4812
Digital value of DAC (0-4095) for MCP4821/MCP4822
DAC bit resolution
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
a higher offset is desired.
The equation can be simplified to:
Step 4: Next solve for R
V
DD
OUT
If R
4096, knowing that the output needs to be +2.05V.
could be used instead of R
1
= 20 k and R
----------------------- -

3
R
and R
R
3
R
+
3
–
-------- -
If R
R
R
4
R
illustrates a simple bipolar voltage source
R
4
1
2
V
4
4
4
1

DD
=
= 20 k, then R
and R
shift the DAC’s output to a selected
=
---------------- -
4.096V
–
2.05V
-------------------------------------------------------
2.05
2
R
2
= 10 k, the gain will be 0.5.
 2010 Microchip Technology Inc.
3
1
V
0.1 µF
allow the gain to be selected,
1.5 4.096V
and R
IN
+
+


0.5 4.096V
4
4
V
, or in addition to R
V
3

by setting the DAC to
R
CC
CC
R
----- -
R
= 10 k
2
DD
2
1
+
–
=
, instead of V
1
-- -
2

=
2
-- -
3
V
O
4
SS
, if
,