MCP4017 datasheet(31/66 Pages) MICROCHIP

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DS22147A-page 31

MCP4017/18/19

4.0

GENERAL OVERVIEW

The MCP4017/18/19 devices are general purpose

digital potentiometers intended to be used in

applications where a programmable resistance with

moderate bandwidth is desired.

This Data Sheet covers a family of three Digital

Potentiometer and Rheostat devices. The MCP4018

device is the Potentiometer configuration, while the

MCP4017 and MCP4019 devices are the Rheostat

configuration.

Applications generally suited for the MCP401X devices

include:

• Set point or offset trimming

• Sensor calibration

• Selectable gain and offset amplifier designs

• Cost-sensitive mechanical trim pot replacement

As the Device Block Diagram shows, there are four

main functional blocks. These are:

• POR/BOR Operation

• Serial Interface - I2C Module

• Resistor Network

The POR/BOR operation and the Memory Map are

discussed in this section and the I2C and Resistor

Network operation are described in their own sections.

The Serial Commands commands are discussed in

Section 5.4.

4.1

POR/BOR Operation

The Power-on Reset is the case where the device is

having power applied to it from VSS. The Brown-out

Reset occurs when a device had power applied to it,

and that power (voltage) drops below the specified

range.

The devices RAM retention voltage (VRAM) is lower

than the POR/BOR voltage trip point (VPOR/VBOR). The

maximum VPOR/VBOR voltage is less then 1.8V.

When VPOR/VBOR < VDD < 2.7V, the Resistor Network’s

electrical performance may not meet the data sheet

specifications. In this region, the device is capable of

reading and writing to its volatile memory if the proper

serial command is executed.

Table 4-1 shows the digital pot’s level of functionality

across the entire VDD range, while Figure 4-1 illustrates

the Power-up and Brown-out functionality.

4.1.1

POWER-ON RESET

When the device powers up, the device VDD will cross

the VPOR/VBOR voltage. Once the VDD voltage crosses

the VPOR/VBOR voltage, the following happens:

• Volatile wiper register is loaded with the default

wiper value (3Fh)

• The device is capable of digital operation

4.1.2

BROWN-OUT RESET

When the device powers down, the device VDD will

cross the VPOR/VBOR voltage. Once the VDD voltage

decreases below the VPOR/VBOR voltage the following

happens:

• Serial Interface is disabled

If the VDD voltage decreases below the VRAM voltage

the following happens:

• Volatile wiper registers may become corrupted

As the voltage recovers above the VPOR/VBOR voltage

see Section 4.1.1 “Power-on Reset”.

Serial commands not completed due to a Brown-out

condition may cause the memory location to become

corrupted.

4.1.3

WIPER REGISTER (RAM)

The Wiper Register is volatile memory that starts

functioning at the RAM retention voltage (VRAM). The

Wiper Register will be loaded with the default wiper

value when VDD will rise above the VPOR/VBOR voltage.

4.1.4

DEVICE CURRENTS

The current of the device can be classified into two

modes of the device operation. These are:

• Serial Interface Inactive (Static Operation)

• Serial Interface Active

Static Operation occurs when a Stop condition is

received. Static Operation is exited when a Start

condition is received.

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