MCP4441 datasheet(41/94 Pages) MICROCHIP

41 / 94 page

 2010 Microchip Technology Inc.

DS22267A-page 41

MCP443X/5X

4.0

FUNCTIONAL OVERVIEW

This data sheet covers a family of four volatile Digital

Potentiometer and Rheostat devices that will be

referred to as MCP44XX. The MCP44X1 devices are

the Potentiometer configuration, while the MCP44X2

devices are the Rheostat configuration.

As the Device Block Diagram shows, there are four

main functional blocks. These are:

• POR/BOR and RESET Operation

• Memory Map

• Resistor Network

• Serial Interface (I2C)

The POR/BOR operation and the Memory Map are

discussed in this section and the Resistor Network and

I2C operation are described in their own sections. The

Device Commands commands are discussed in

Section 7.0.

4.1

POR/BOR and RESET 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 electrical perfor-

mance may not meet the data sheet specifications. In

this region, the device is capable of incrementing, dec-

rementing, reading and writing to its volatile memory if

the proper serial command is executed.

When VDD < VPOR/VBOR or the RESET pin is Low, the

pin weak pull-ups are enabled.

4.1.1

POWER-ON RESET

When the device powers up, the device VDD crosses

the VPOR/VBOR voltage.

When the VDD voltage crosses the VPOR/VBOR voltage,

the following events occur:

• Volatile wiper register is loaded with the default

value

• TCON registers are loaded with their default value

• Device is capable of digital operation

4.1.2

BROWN-OUT RESET

When the device powers down, device VDD will cross

VPOR/VBOR voltage.

When VDD voltage decreases below VPOR/VBOR

voltage, the serial Interface is disabled.

If the VDD voltage decreases below VRAM voltage, the

following events may occur:

• Volatile wiper registers could become corrupted

• TCON registers could become corrupted

As the voltage recovers above the VPOR/VBOR voltage,

the operation is the same as Power-on Reset, as dis-

cussed in the previous subsection.

Serial commands that are not completed because of a

brown-out condition could cause the memory location

to become corrupted.

4.1.3

RESET PIN

The RESET pin can be used to force the device into

the POR/BOR state of the device. When the RESET

pin is forced Low, the device is forced into the Reset

state. This means that the TCON registers are forced

to their default values and the volatile wiper registers

are loaded with the default value. Also the I2C inter-

face is disabled.

This feature allows a hardware method for all registers

to be updated at the same time.

4.1.4

INTERACTION OF RESET PIN AND

BOR/POR CIRCUITRY

Figure 4-1 shows how the RESET pin signal and the

POR/BOR signal interact to control the hardware Reset

state of the device.

FIGURE 4-1:

POR/BOR Signal and

RESET Pin Interaction.

RESET (from pin)

POR/BOR signal

Device Reset

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