Datasheet

Detailed Description
The MAX5422/MAX5423/MAX5424 contain a resistor
array with 255 resistive elements. The MAX5422 has a
total end-to-end resistance of 50kΩ; the MAX5423 has
an end-to-end resistance of 100kΩ; and the MAX5424
has an end-to-end resistance of 200kΩ. The
MAX5422/MAX5423/MAX5424 allow access to the high,
low, and wiper terminals for a standard voltage-divider
configuration. H, L, and W can be connected in any
desired configuration as long as their voltages fall
between GND and V
DD
.
A simple, 3-wire, SPI serial interface moves the wiper
among the 256 tap points. The nonvolatile memory
stores the wiper position and recalls the stored wiper
position upon power-up. The nonvolatile memory is
guaranteed for 50 years for wiper data retention and up
to 200,000 wiper store cycles.
Analog Circuitry
The MAX5422/MAX5423/MAX5424 consist of a resistor
array with 255 resistive elements; 256 tap points are
accessible to the wiper, W, along the resistor string
between H and L. Select the wiper tap point by pro-
gramming the potentiometer through the 3-wire (SPI)
interface. Eight data bits, and a control byte program
the wiper position. The H and L terminals of the
MAX5422/MAX5423/MAX5424 are similar to the two
end terminals of a mechanical potentiometer. The
MAX5422/MAX5423/MAX5424 feature power-on reset
circuitry that loads the wiper position from the non-
volatile memory at power-up.
Digital Interface
The MAX5422/MAX5423/MAX5424 use a 3-wire, SPI-
compatible, serial data interface (Figure 1 and 2). This
write-only interface contains three inputs: chip-select
MAX5422/MAX5423/MAX5424
256-Tap, Nonvolatile, SPI-Interface,
Digital Potentiometers
_______________________________________________________________________________________ 7
PIN NAME FUNCTION
1V
DD
Power-Supply Input. Bypass V
DD
with a 0.1µF capacitor from V
DD
to GND.
2 SCLK Serial-Interface Clock Input
3 DIN Serial-Interface Data Input
4 CS Active-Low Digital-Input Chip Select
5 GND Ground
6L
Low Terminal. The voltage at L can be greater than or less than the voltage at H. Current can flow into or
out of L.
7 W Wiper Terminal
8H
High Terminal. The voltage at H can be greater than or less than the voltage at L. Current can flow into or
out of H.
— EP Exposed Pad. The exposed pad is not internally connected. Connect to GND or leave floating.
Pin Description
SCLK
CS
DIN
t
CS0
t
DS
t
CL
t
CH
t
DH
t
CP
t
CSH
t
CS1
t
CSW
t
CSS
Figure 1. Digital Interface and Timing Diagram