MCP4021 datasheet(28/64 Pages) MICROCHIP

28 / 64 page

MCP4021/2/3/4

DS21945E-page 28

4.2

The WiperLock™ Technology

The MCP4021/2/3/4 device’s WiperLock technology

allows application-specific calibration settings to be

secured in the EEPROM without requiring the use of an

additional write-protect pin.

The WiperLock technology prevents the serial

commands from doing the following:

• Incrementing or decrementing the wiper setting

• Writing the wiper setting to the non-volatile

memory

Enabling and disabling the WiperLock technology

feature

requires

high-voltage

serial

commands

(CS =VIHH). Incrementing and decrementing the wiper

requires high-voltage commands when the feature is

enabled. The high-voltage threshold (VIHH) is intended

to prevent the wiper setting from being altered by noise

or intentional transitions on the U/D and CS pins, while

still providing flexibility for production or calibration

environments.

Both the CS and U/D input pins are tolerant of signals

up to 12V. This allows the flexibility to multiplex the

digital pot’s control signals onto application signals for

manufacturing/calibration.

4.3

Power-up

When the device powers up, the last saved wiper

setting is restored.

While VDD < Vmin (2.7V), the electrical performance

may not meet the data sheet specifications (see

Figure 4-2). The wiper may be unknown or initialized to

the value stored in the EEPROM. Also the device may

be capable of incrementing, decrementing and writing

to its EEPROM, if a valid command is detected on the

CS and U/D pins.

The default settings of the MCP4021/2/3/4 device’s

from the factory are shown in Table 4-1.

TABLE 4-1:

DEFAULT FACTORY

SETTINGS SELECTION

It is good practice in your manufacturing flow to

configure the device to your desired settings.

4.4

Brown Out

If the device VDD is below the specified minimum

voltage, care must be taken to ensure that the CS and

U/D pins do not “create” any of the serial commands.

When the device VDD drops below Vmin (2.7V), the

electrical performance may not meet the data sheet

specifications (see Figure 4-2). The wiper may be

unknown or initialized to the value stored in the

EEPROM. Also the device may be capable of

incrementing, decrementing and writing to its EEPROM

if a valid command is detected on the CS and U/D pins.

4.5

Serial Interface Inactive

The serial interface is inactive any time the CS pin is at

VIH and all write cycles are completed.

FIGURE 4-2:

Power-up and Brown-out.

-202

Mid-scale

1Fh

Disabled

2.1 k

-502

Mid-scale

1Fh

Disabled

5.0 k

-103

Mid-scale

1Fh

Disabled

10.0 k

-503

Mid-scale

1Fh

Disabled

50.0 k

VWP

VSS

VDD

2.7V

EEPROM

Write

Protect

Outside

Specified AC/DC

Range

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