MCP4716 datasheet(53/70 Pages) MICROCHIP

53 / 70 page

 2012 Microchip Technology Inc.

DS25154A-page 53

MCP47A1

8.6.2

PCB AREA REQUIREMENTS

In some applications, PCB area is a criteria for device

selection.

Table 8-2

shows

the

typical

package

dimensions and area for the different package options.

TABLE 8-2:

PACKAGE FOOTPRINT (1)

8.6.3

PINOUT/FOOTPRINT

COMPATIBILITY

The MCP47A1 has a pinout and footprint compatibility

to the MCP40D18 and MCP4018 devices.

The MCP40D18/MCP4018’s W pin is analogous to the

MCP47A1’s

VOUT

pin,

while

the

MCP40D18/

MCP4018’s A pin is analogous to the MCP47A1’s VREF

pin. The MCP40D18 and MCP47A1 share the same

I2C command protocol structure.

8.6.4

CONNECTING TO I2C BUS USING

PULL-UP RESISTORS

The SCL and SDA pins of the MCP47A1 devices are

open-drain configurations. These pins require a pull-up

resistor as shown in Figure 8-9.

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

I2C 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 k

and 10 kranges for standard

and fast modes.

8.6.4.1

Device Connection Test

The user can test the presence of the device on the I2C

bus line using a simple I2C command. This test can be

achieved by checking an acknowledge response from

the device after sending a read or write command.

Figure 8-10 shows an example with a read command.

The steps are:

Set the R/W bit “High” in the device’s address

byte.

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.

Send Stop bit.

FIGURE 8-10:

I2C Bus Connection Test.

Package

Package Footprint

Type

Code

Dimensions (mm)

Length

Width

SC70

3.10

3.20

9.92

Note 1: Does not include recommended Land

Pattern dimensions. Dimensions are Max

values.

SCL

SDA

1A2 A1 A0 1

Start

Bit

Address Byte

Address bits

Device Code

R/W

Stop

Bit

Device

Response

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