Datasheet

© 2011-2012 Microchip Technology Inc. DS22272C-page 63
MCP4706/4716/4726
8.0 TYPICAL APPLICATIONS
The MCP47X6 family of devices are general purpose,
single channel voltage output DACs for various
applications where a precision operation with
low-power and nonvolatile EEPROM memory is
needed.
Since the devices include a nonvolatile EEPROM
memory, the user can utilize these devices for
applications that require the output to return to the
previous set-up value on subsequent power-ups.
Applications generally suited for the devices are:
• Set Point or Offset Trimming
• Sensor Calibration
• Portable Instrumentation (Battery Powered)
• Motor Control
8.1 Connecting to I
2
C BUS using
Pull-Up Resistors
The SCL and SDA pins of the MCP47X6 devices are
open-drain configurations. These pins require a pull-up
resistor as shown in Figure 8-2.
The pull-up resistor values (R1 and R2) for SCL and
SDA pins depend on the operating speed (standard,
fast, and high speed) and loading capacitance of the
I
2
C bus line. A higher value of the pull-up resistor
consumes less power, but increases the signal
transition time (higher RC time constant) on the bus
line. Therefore, it can limit the bus operating speed.
The lower resistor value, on the other hand, consumes
higher power, but allows higher operating speed. If the
bus line has higher capacitance due to long metal
traces or multiple device connections to the bus line, a
smaller pull-up resistor is needed to compensate the
long RC time constant. The pull-up resistor is typically
chosen between 1 kΩ and 10 kΩ ranges for Standard
and Fast modes, and less than 1 kΩ for High-Speed
mode.
8.1.1 DEVICE CONNECTION TEST
The user can test the presence of the device on the I
2
C
bus line using a simple I
2
C command. This test can be
achieved by checking an acknowledge response from
the device after sending a Read or Write command.
Figure 8-1 shows an example with a Read command.
The steps are:
a) Set the R/W
bit “High” in the device’s address
byte.
b) Check the ACK bit of the address byte.
If the device acknowledges (ACK = 0) the
command, then the device is connected,
otherwise it is not connected.
c) Send Stop bit.
FIGURE 8-1: I
2
C Bus Connection Test.
123456789
SCL
SDA
1
1
0
1 A2 A1 A0
1
Start
Bit
Address Byte
Address bits
Device Code
R/W
Stop
Bit
Device
ACK
Response