MCP4725 Microchip Technology, MCP4725 Datasheet - Page 32

• Manufacturer Part Number: MCP4725
• Description: 12-Bit Digital-to-Analog Converter
• Manufacturer: Microchip Technology

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MCP4725
8.5.4.1
Some applications desires an output step magnitude of
1 mV with an output range of ±2.05V. The following
steps explain the design solution:
1.
2.
3.
4.
DS22039C-page 32
If R
If R
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
the V
4.1V is used, solve for the amplifier’s gain by
setting the DAC to 0, knowing that the output
needs to be -2.05V. The equation can be
simplified to:
Next, solve for R
4096, knowing that the output needs to be
+2.05V.
1
4
= 20 kΩ and R
= 20 kΩ, then R
---------------------- -
(
DD
R
3
12
–
-------- -
R
R
value must be selected first. If a V
+
R
Design a Bipolar DAC using
Example 8-3
4
1
= 4096 for 12-bit resolution.
2
R
=
4
)
–
------------ -
V
2.05
=
DD
2
3
2.05V
----------------------------------------------- -
3
= 10 kΩ, the gain will be 0.5.
and R
= 10 kΩ
=
1.5 V
2
–
------------ -
/R
+
2.05
4.1
4
(
1
⋅
0.5 V
by setting the DAC to
), multiplied by V
→
DD
⋅
R
----- -
R
DD
2
1
=
)
1
-- -
2
=
2
-- -
3
1
+R
DD
DD
2
of
),
,
© 2007 Microchip Technology Inc.