MCP4641-104ESLASHST datasheet(44/92 Pages) MICROCHIP

44 / 92 page

MCP454X/456X/464X/466X

DS22107A-page 44

5.2

Wiper

Each tap point (between the RS resistors) is a

connection point for an analog switch. The opposite

side of the analog switch is connected to a common

signal which is connected to the Terminal W (Wiper)

pin.

A value in the volatile wiper register selects which

analog switch to close, connecting the W terminal to

the selected node of the resistor ladder.

The wiper can connect directly to Terminal B or to

Terminal A. A zero-scale connections, connects the

Terminal W (wiper) to Terminal B (wiper setting of

000h). A full-scale connections, connects the Terminal

W (wiper) to Terminal A (wiper setting of 100h or 80h).

In these configurations the only resistance between the

Terminal W and the other Terminal (A or B) is that of

the analog switches.

A wiper setting value greater than full-scale (wiper

setting of 100h for 8-bit device or 80h for 7-bit devices)

will also be a Full-Scale setting (Terminal W (wiper)

connected to Terminal A). Table 5-1 illustrates the full

wiper setting map.

Equation 5-2 illustrates the calculation used to deter-

mine the resistance between the wiper and terminal B.

EQUATION 5-2:

RWB CALCULATION

TABLE 5-1:

VOLATILE WIPER VALUE VS.

WIPER POSITION MAP

5.3

WiperLock™ Technology

The MCP4XXX 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. There are two WiperLock Technology

configuration bits (WL0 and WL1). These bits prevent

the Non-Volatile and Volatile addresses and bits for the

specified resistor network from being written.

The

WiperLock

technology

prevents

the

serial

commands from doing the following:

• Changing a volatile wiper value

• Writing to a non-volatile wiper memory location

• Changing the volatile TCON register value

For either Resistor Network 0 or Resistor Network 1

(Potx), the WLx bit controls the following:

• Non-Volatile Wiper Register

• Volatile Wiper Register

• Volatile TCON register bits RxHW, RxA, RxW,

and RxB

High Voltage commands are required to enable and

disable WiperLock. Please refer to the Modify Write

Protect or WiperLock Technology (High Voltage)

command for operation.

5.3.1

POR/BOR OPERATION WHEN

WIPERLOCK TECHNOLOGY

ENABLED

The WiperLock Technology state is not affected by a

POR/BOR event. A POR/BOR event will load the

Volatile Wiper register value with the Non-Volatile

Wiper register value, refer to Section 4.1.

Wiper Setting

Properties

7-bit Pot 8-bit Pot

3FFh

081h

3FFh

101h

Reserved (Full-Scale (W = A)),

Increment and Decrement

commands ignored

080h

100h

Full-Scale (W = A),

Increment commands ignored

07Fh

041h

0FFh

081

W = N

040h

080h

W = N (Mid-Scale)

03Fh

001h

07Fh

001

W = N

000h

Zero Scale (W = B)

Decrement command ignored

ABN

256

()

--------------R

N = 0 to 256 (decimal)

ABN

128

()

--------------R

N = 0 to 128 (decimal)

8-bit Device

7-bit Device

MCP4641-104E/ST 数据表(PDF) 44 Page - Microchip Technology

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