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Detailed Description

The DS3503 contains two potentiometers whose out-

puts can be stepped up and down by configuring the

control registers. One potentiometer, with output RW, is

controlled by the Initial Value Register/Wiper Register

(IVR/WR). The other potentiometer is fixed at setting

40h, and its output is on the Y pin. By using the config-

uration registers and the SYNC pin, the outputs from

these two potentiometers can be stepped up and

down.

Digital Potentiometers

The RW potentiometer consists of 127 resistors in

series connected between the RH and RL pins.

Between each resistance and at the two end points, RH

and RL, solid-state switches enable RW to be connect-

ed within the resistive network. The wiper position and

the output on RW are decoded based on the value in

WR. If RH, RL, and RW are externally connected in a

voltage-divider configuration, the voltage on RW can be

easily calculated using the following equation:

Where WR is the wiper position in decimal (0–127). The

factory default setting for this potentiometer is 40h.

The Y potentiometer is also referenced to the RH and

RL terminals, but is centered at a 40h setting.

Memory Map

The DS3503 contains three registers for controlling the

outputs of the two potentiometers, pins RW and Y.

Table 1 shows the memory map. IVR/WR is accessed

at register address 00h and contains the power-on and

current values of the RW potentiometer. The Step

Control Register (SCR) controls the stepping function

for both potentiometers. The Control Register (CR) con-

trols the write functionality of the IVR/WR.

Initial Value Register/Wiper Register

(IVR/WR)

Programming IVR sets the initial power-up value of the

RW wiper position. IVR/WR can be visualized as a

volatile register (WR) in parallel with a nonvolatile regis-

ter (IVR). On power-up, the data stored in IVR is loaded

into WR, which sets the position of the potentiometer’s

wiper. The factory default value for IVR is 40h. See the

Stepping section for information about clamping.

VV

WR

VV

RW

RL

RH

RL

=+

×

−

127

()

NAME

ADDRESS

(HEX)

ACCESS

NONVOLATILE

VOLATILE

IVR/WR

00h

R/W

Initial Value Register (IVR),

factory setting = 40h

Wiper Register (WR)

SCR

01h

R/W

Step Control Register,

factory setting = 00h

—

CR

02h

R/W

Control Register

—

Soft-POR

AAh

R/W

—

Soft Power-On Reset

Register

Table 1. Memory Map