MCP42010-I/ST Microchip Technology Inc., MCP42010-I/ST Datasheet - Page 15

• Manufacturer Part Number: MCP42010-I/ST
• Description: Pot, Digital; Rest 10 Kilohms; Digital; 256 Pos; 14 Pins; 2 Ch; Pkg TSSOP
• Manufacturer: Microchip Technology Inc.
• Type: Digitalr

Specifications of MCP42010-I/ST

• Bandwidth: 1 MHz
• Current, Power Supply: 500 μA
• Nominal Resistance: 10 Kilohms
• Number Of Channels: 2
• Number Of Pins: 14
• Number Of Positions: 256
• Package Type: TSSOP
• Resolution: 8 Bits
• Temperature, Operating, Maximum: +85 °C
• Temperature, Operating, Minimum: -40 °C
• Voltage, Range: 2.7 to 5.5 VDC
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

4.2
4.2.1
Potentiometers are often used to adjust system refer-
ence levels or gain. Programmable gain circuits using
digital potentiometers can be realized in a number of
different ways. An example of a single-supply, inverting
gain amplifier is shown in Figure 4-4. Due to the high
input impedance of the amplifier, the wiper resistance
is not included in the transfer function. For a single-sup-
ply, non-inverting gain configuration, the circuit in
Figure 4-5 can be used.
.
FIGURE 4-4:
programmable, inverting gain amplifier using a
digital potentiometer.
FIGURE 4-5:
programmable, non-inverting gain amplifier.
R
R
D
Where:
2003 Microchip Technology Inc.
V
V
A
AB
n
IN
IN
=
=
=
Wiper setting forD
R
R
D
Where:
R
-------------------------------------- -
V
Typical Applications
Total Resistance of pot
A
AB
n
AB
V
OUT
MCP41010
PROGRAMMABLE SINGLE-ENDED
AMPLIFIERS
REF
=
=
A
W
=
256 D
256
RA
Wiper setting forD
MCP41010
R
-------------------------------------- -
=
Total Resistance of pot
AB
+IN
–
–
-IN
+IN
-IN
W
V
256 D
B
256
IN
RB
n
+
-
MCP606
Single-supply,
+
MCP606
Single-supply,
-
R
------ -
R
–
B
A
R
n
V
n
B
V
=
V
V
SS
V
+
DD
SS
OUT
=
0 to 255
DD
V
R
REF
R
----------------- -
n
B
256
AB
=
=
=
0 to 255
D
1
V
n
R
----------------- -
IN
+
AB
256
R
------ -
R
1
B
A
D
+
n
V
R
------ -
R
V
OUT
B
A
OUT
In order for these circuits to work properly, care must be
taken in a few areas. For linear operation, the analog
input and output signals must be in the range of V
V
the op-amp. The circuit in Figure 4-4 requires a virtual
ground or reference input to the non-inverting input of
the amplifier. Refer to Application Note 682, “Using
Single-Supply Operational Amplifiers in Embedded
Systems” (DS00682), for more details. At power-up or
reset (RS), the resistance is set to mid-scale, with R
and R
circuit, the gain is -1 V/V. As the code is increased and
the wiper moves towards the A terminal, the gain
increases. Conversely, when the wiper is moved
towards the B terminal, the gain decreases. Figure 4-6
shows this relationship. Notice the pseudo-logarithmic
gain around decimal code 128. As the wiper
approaches either terminal, the step size in the gain
calculation
mismatched ratio of R
low codes, small increments in wiper position can
dramatically affect the gain. As shown in Figure 4-3,
recommended gains lie between 0.1 and 10 V/V.
FIGURE 4-6:
and differential amplifier circuits.
4.2.2
An example of a differential input amplifier using digital
potentiometers is shown in Figure 4-7. For the transfer
function to hold, both pots must be programmed to the
same code. The resistor-matching from channel-to-
channel within a dual device can be used as an advan-
tage in this circuit. This circuit will also show stable
operation over temperature due to the low potentiome-
ter temperature coefficient. Figure 4-6 also shows the
relationship between gain and code for this circuit. As
the wiper approaches either terminal, the step size in
the gain calculation increases dramatically. This circuit
is recommended for gains between 0.1 and 10 V/V.
DD
for the potentiometer and input and output rails of
B
MCP41XXX/42XXX
0.1
10
matching. Based on the transfer function for the
1
0
PROGRAMMABLE DIFFERENTIAL
AMPLIFIER
increases
64
Decimal code (0-255)
A
Gain vs. Code for inverting
and R
dramatically.
128
B
at the extreme high and
DS11195C-page 15
192
Due
to
256
SS
the
to
A