MCP453X Datasheet, PDF (63/88 Pages) Microchip Technology – 7/8-Bit Single/Dual I2C Digital POT with Volatile Memory

MCP453X/455X/463X/465X
8.0 APPLICATIONS EXAMPLES
Non-volatile digital potentiometers have a multitude of
practical uses in modern electronic circuits. The most
popular uses include precision calibration of set point
thresholds, sensor trimming, LCD bias trimming, audio
attenuation, adjustable power supplies, motor control
overcurrent trip setting, adjustable gain amplifiers and
offset trimming. The MCP453X/455X/463X/465X
devices can be used to replace the common mechani-
cal trim pot in applications where the operating and
terminal voltages are within CMOS process limitations
(V_DD = 2.7V to 5.5V).
8.1 Techniques to force the HVC pin
to V_IHH
The circuit in Figure 8-1 shows a method using the
TC1240A doubling charge pump. When the SHDN pin
is high, the TC1240A is off, and the level on the HVC
pin is controlled by the PIC^® microcontrollers (MCUs)
IO2 pin.
When the SHDN pin is low, the TC1240A is on and the
V_OUT voltage is 2 * V_DD. The resistor R₁ allows the
HVC pin to go higher than the voltage such that the PIC
MCU’s IO2 pin “clamps” at approximately VDD.
PIC MCU
IO1
IO2
TC1240A
V_IN
C+
SHDN ^C-
C₁
V_OUT
MCP45XX
R₁
HVC ^MCP46XX
C₂
FIGURE 8-1:
Using the TC1240A to
generate the V_IHH voltage.
The circuit in Figure 8-2 shows the method used on the
MCP402X Non-volatile Digital Potentiometer Evalua-
tion Board (Part Number: MCP402XEV). This method
requires that the system voltage be approximately 5V.
This ensures that when the PIC10F206 enters a
brown-out condition, there is an insufficient voltage
level on the HVC pin to change the stored value of the
wiper. The MCP402X Non-volatile Digital Potentiome-
ter Evaluation Board User’s Guide (DS51546) contains
a complete schematic.
GP0 is a general purpose I/O pin, while GP2 can either
be a general purpose I/O pin or it can output the internal
clock.
For the serial commands, configure the GP2 pin as an
input (high impedance). The output state of the GP0 pin
will determine the voltage on the HVC pin (V_IL or V_IH).
For high-voltage serial commands, force the GP0
output pin to output a high level (V_OH) and configure the
GP2 pin to output the internal clock. This will form a
charge pump and increase the voltage on the HVC pin
(when the system voltage is approximately 5V).
PIC10F206
GP0
R₁
MCP4XXX
GP2
C₁
HVC
C₂
FIGURE 8-2:
MCP4XXX Non-Volatile
Digital Potentiometer Evaluation Board
(MCP402XEV) implementation to generate the
V_IHH voltage.
© 2008 Microchip Technology Inc.
DS22096A-page 63