MCP4812T-E/MS Microchip Technology, MCP4812T-E/MS Datasheet - Page 28

• Manufacturer Part Number: MCP4812T-E/MS
• Description: Dual 10-bit DAC With SPI Interace And Internal Vref 8 MSOP 3x3mm T/R
• Manufacturer: Microchip Technology

Specifications of MCP4812T-E/MS

• Settling Time: 4.5µs
• Number Of Bits: 10
• 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: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power Dissipation (max): -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MCP4802/4812/4822
6.6
Bipolar
MCP4802/4812/4822 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
DS22249A-page 28
(a) Single Output DAC:
(b) Dual Output DAC:
V OUT
V
desired.
scale V
desired minimum output to achieve bipolar
operation. Since any gain can be realized by
choosing resistor values (R
value must be selected first. If a V
is used (G=2), solve for the amplifier’s gain by
setting the DAC to 0, knowing that the output
needs to be -2.05V.
4.1V/1 mV = 4100
Since 2
Bipolar Operation
IN+
V
operation
operational
O
DESIGN EXAMPLE: DESIGN A
BIPOLAR DAC USING
WITH 12-BIT MCP4822 OR
MCP4821
=
=
=
2.048 G
V
------------------- -
V
OUT
R
12
OUT
IN+
3
+
MCP4801
MCP4811
MCP4821
MCP4802
MCP4812
MCP4822


= 4096, 12-bit resolution is
(4.096V), must be equal to the
R
R

1
4
DIGITALLY-CONTROLLED BIPOLAR VOLTAGE SOURCE
4
is
+
amplifier

R
----- -
R
D
------
2
2
1
N


n
achievable
–
2
V
/R
DD
1
), multiplied by full-


(op
R
----- -
R
1
EXAMPLE 6-3
2
1
SPI
+R


REF
2
amp).
), the V
using
of 4.096V
3-wire
This
V
D
REF
G
the
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
V
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
OUT
DD
If R
could be used instead of R
1
= 20 k and R
----------------------- -

3
4096, knowing that the output needs to be
+2.05V.
R
R
and R
3
3
R
R
+
–
-------- -
If R
R
4
4
R
illustrates a simple bipolar voltage source
R
V
1
2
4
DD
4
4
1

=
= 20 k, then R
and R
shift the DAC's output to a selected
=
---------------- -
4.096V
–
2.05V
-------------------------------------------------------
2.05
R
2
1
2
V
= 10 k, the gain will be 0.5.
0.1 µF
 2010 Microchip Technology Inc.
3
allow the gain to be selected,
IN
1.5 4.096V
and R
+
+


0.5 4.096V
V
V
4,
4
R
CC
CC
3

or in addition to R
by setting the DAC to
2
R
----- -
R
= 10 k
+
–
DD
2
1
=
, instead of V
1
-- -
2

=
2
-- -
3
V
O
4
SS
, if
,