MCP4432-503ESLASHML datasheet(46/94 Pages) MICROCHIP

46 / 94 page

MCP443X/5X

DS22267A-page 46

 2010 Microchip Technology Inc.

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 connection, 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

determine 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

Shutdown

Shutdown is used to minimize the device’s current

consumption. The MCP44XX has one method to

achieve this. This is:

• Terminal Control Register (TCON)

This is different from the MCP42XXX devices in that the

Hardware Shutdown Pin (SHDN) has been replaced by

a RESET pin. The Hardware Shutdown Pin function is

still available via software commands to the TCON

5.3.1

TERMINAL CONTROL REGISTER

(TCON)

The Terminal Control (TCON) register is a volatile

resistor network terminal pin (A, B, and W) to the

Resistor Network. These registers are shown in

The RxHW bits forces the selected resistor network

into the same state as the MCP42X1’s SHDN pin.

Alternate low power configurations may be achieved

with the RxA, RxW, and RxB bits.

When the RxHW bit is ‘0’:

• The P0A, P1A, P2A, and P3A terminals are

disconnected

• The P0W, P1W, P2W, and P3W terminals are

simultaneously connect to the P0B, P1B, P2B,

and P3B terminals, respectively (see Figure 5-2)

The RxHW bit does NOT corrupt the values in the

Volatile Wiper Registers nor the TCON register. When

the Shutdown mode is exited (RxHW bit = 1):

• The device returns to the Wiper setting specified

by the Volatile Wiper value

• The TCON register bits return to controlling the

terminal connection state

FIGURE 5-2:

Resistor Network Shutdown

State (RxHW = ‘

0’).

Wiper Setting

Properties

7-bit

8-bit

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 –

081h

W = N

040h

080h

W = N (Mid Scale)

03Fh –

001h

07Fh –

001h

W = N

000h

Zero Scale (W = B)

Decrement command ignored

RWB

RABN

256



--------------

N = 0 to 256 (decimal)

RWB

RABN

128



--------------

N = 0 to 128 (decimal)

8-bit Device

7-bit Device

Note:

When the RxHW bit forces the resistor

network into the hardware SHDN state,

the state of the TCON0 or TCON1

overridden (ignored). When the state of

the RxHW bit no longer forces the resistor

network into the hardware SHDN state,

the TCON0 or TCON1 register’s RxA,

RxW, and RxB bits return to controlling the

terminal connection state. In other words,

the RxHW bit does not corrupt the state of

the RxA, RxW, and RxB bits.

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