MCP4725 datasheet(27/42 Pages) MICROCHIP

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DS22039C-page 27

MCP4725

8.0

TYPICAL APPLICATIONS

The MCP4725 device is one of Microchip’s latest DAC

device family with non-volatile EEPROM memory. The

device is a general purpose resistive string DAC

intended to be used in applications where a precision,

and low power DAC with moderate bandwidth is

required.

Since the device includes non-volatile EEPROM

memory, the user can use this device for applications

that require the output to return to the previous set-up

value on subsequent power-ups.

Applications generally suited for the MCP4725 device

family include:

• Set Point or Offset Trimming

• Sensor Calibration

• Portable Instrumentation (Battery Powered)

• Motor Speed Control

8.1

Connecting to I2C BUS using

Pull-Up Resistors

The SCL and SDA pins of the MCP4725 are open-drain

configurations. These pins require a pull-up resistor as

shown in Figure 8-1. The value of these pull-up

resistors depends on the operating speed (standard,

fast, and high speed) and loading capacitance of the

I2C bus line. Higher value of pull-up resistor consumes

less power, but increases the signal transition time

(higher RC time constant) on the bus. 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 bus line or high number of

devices connected to the bus, a smaller pull-up resistor

is needed to compensate the long RC time constant.

The pull-up resistor is typically chosen between 1 k

and 10 k

Ω ranges for standard and fast modes, and

less than 1 k

Ω for high speed mode.

FIGURE 8-1:

I2C Bus Interface

Connection with A0 pin tied to VSS.

Two devices with the same A2 and A1 address bits can

be connected to the same I2C bus by utilizing the A0

address pin (Example: A0 pin of device A is tied to VDD,

and the other device’s pin is tied to VSS.)

8.1.1

DEVICE CONNECTION TEST

The user can test the presence of the MCP4725 on the

I2C bus line without performing the data conversion.

This test can be achieved by checking an acknowledge

response from the MCP4725 after sending a read or

write command. Here is an example using Figure 8-2:

(a) Set the R/W bit “HIGH” in the address byte.

(b) If the MCP4725 is connected to the I2C bus line, it

will then acknowledge by pulling SDA bus LOW

during the ACK clock and then release the bus

back to the I2C Master.

from the Master and I2C communication can con-

tinue.

FIGURE 8-2:

I2C Bus Connection Test.

MCP4725

VOUT

SCL

VSS

VDD

SDA

10 µF

0.1 µF

Analog

VDD

To MCU

(MASTER)

Output

Note 1: R is the pull-up resistor. Typically

1 ~ 10 k

2: A0 can be tied to V

SS, VDD or driven by

MCU

SCL

SDA

0A2 A1 A0 1

Start

Bit

Address Byte

Address bits

Device bits

R/W

Start

Bit

MCP4725

Response

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