Datasheet

Detailed Description
Each potentiometer consists of 255 fixed resistors in
series between pins H
B
and L
B
for the 3-terminal
potentiometer and between W
A
and L
A
for the 2-termi-
nal variable resistor (Figure 1). The potentiometer wiper
(pin W
X
) can be programmed to access any one of the
256 different tap points on the resistor string. The
MAX5403/MAX5404/MAX5405 require nine bits to pro-
gram the wiper position. The 1st bit is an address code,
allowing one or the other potentiometers to be selected
for programming. The potentiometers are programmed
independently of each other.
The MAX5403/MAX5404/MAX5405 use a 3-wire serial
data interface to control the wiper tap position. This
write-only interface contains three inputs: Chip Select
(CS), Data In (DIN), and Data Clock (SCLK). When CS
is taken low, data from the DIN pin is synchronously
loaded into the serial shift register on each rising edge
MAX5403/MAX5404/MAX5405
Dual 256-Tap, Low-Drift,
Digital Potentiometers in 10-µMAX
_______________________________________________________________________________________ 7
Pin Description
PIN NAME FUNCTION
1 GND Ground
2L
B
Low Terminal of Resistor B
3H
B
High Terminal of Resistor B
4W
B
Wiper Terminal of Resistor B
5 CS SPI Chip Select
6 DIN SPI Serial Data Input
7 SCLK SPI Clock Input
8V
DD
Power Supply, +2.7V to +5.5V. Connect a 0.1µF capacitor to GND.
9W
A
Wiper Terminal of Resistor A
10 L
A
Low Terminal of Resistor A
V
DD
GND
DIN
SCLK
9-BIT
SHIFT
REGISTER
R
8-BIT
LATCH
R
8-BIT
LATCH
R
SR
DECODE
CS
88
8
256
256
W
A
L
A
L
B
H
B
W
B
POR
DECODE
DECODE
MAX5403
MAX5404
MAX5405
Figure 1. MAX5403/MAX5404/MAX5405 Functional Diagram: 2-Terminal Variable Resistor and 3-Terminal Potentiometers in 10-µMAX
Configuration