MCP4531 datasheet(37/88 Pages) MICROCHIP

37 / 88 page

DS22096A-page 37

MCP453X/455X/463X/465X

4.0

FUNCTIONAL OVERVIEW

This Data Sheet covers a family of thirty-two Digital

Potentiometer and Rheostat devices that will be

referred to as MCP4XXX. The MCP4XX1 devices are

the Potentiometer configuration, while the MCP4XX2

devices are the Rheostat configuration.

As the Device Block Diagram shows, there are four

main functional blocks. These are:

• POR/BOR 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 “Device Commands”.

4.1

POR/BOR Operation

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

having power applied to it starting from the VSS level.

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 than 1.8V.

When VPOR/VBOR < VDD < 2.7V, the electrical

performance

may

not

meet

the

data

sheet

specifications. In this region, the device is capable of

incrementing, decrementing, reading and writing to its

volatile memory if the proper serial command is exe-

cuted.

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 value in the

corresponding non-volatile wiper register

• The TCON register is loaded it’s default value

• 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 Serial Interface is disabled.

If the VDD voltage decreases below the VRAM voltage

the following happens:

• Volatile wiper registers may become corrupted

• TCON register 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 volatile memory location to

become corrupted.

4.2

Memory Map

The device memory map supports 16 locations, of

which 3 locations are used. Each location is 9-bits wide

(16x9 bits). This memory space is shown in Table 4-1.

TABLE 4-1:

MEMORY MAP

4.2.1

VOLATILE MEMORY (RAM)

There are four Volatile Memory locations. These are:

• Volatile Wiper 0

• Volatile Wiper 1

(Dual Resistor Network devices only)

• Terminal Control (TCON) Register

• Reserved

The volatile memory starts functioning at the RAM

retention voltage (VRAM).

4.2.1.1

Address 05h (Reserved)

This memory location is Reserved and is mapped to

the Status Register of the Non-Volatile MCP45XX/

46XX devices. Since the Non-Volatile devices bits are

not used by the volatile device, this location is

reserved. Reading this address wil result in a value of

1F7h.

Address

Function

Memory Type

00h

Volatile Wiper 0

RAM

01h

Volatile Wiper 1

RAM

02h

Reserved

—

03h

Reserved

—

04h

Volatile TCON Register

RAM

05h

Reserved

RAM

06h - 0Fh Reserved

—

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