Datasheet

MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I
2
C-Interface,
Digital Potentiometers
10 ______________________________________________________________________________________
Detailed Description
The MAX5477/MAX5478/MAX5479 contain two resistor
arrays with 255 elements in each array. The MAX5477
has a total end-to-end resistance of 10kΩ , the
MAX5478 has an end-to-end resistance of 50kΩ, and
the MAX5479 has an end-to-end resistance of 100kΩ.
The MAX5477/MAX5478/MAX5479 provide access to
the high, low, and wiper terminals for a standard volt-
age-divider configuration. Connect H_, L_, and W_ in
any desired configuration as long as their voltages
remain between GND and V
DD
.
A simple 2-wire I
2
C-compatible serial interface moves
the wiper among the 256 tap points (Figure 2). A non-
volatile memory stores the wiper position and recalls
the stored wiper position upon power-up. The non-
volatile memory is guaranteed for 50 years for wiper
data retention and up to 200,000 wiper store cycles.
Analog Circuitry
The MAX5477/MAX5478/MAX5479 consist of two resistor
arrays with 255 resistive elements; 256 tap points are
accessible to the wipers, along the resistor string
between H_ and L_. The wiper tap point is selected by
programming the potentiometer through the I
2
C inter-
face. An address byte, a command byte, and 8 data bits
program the wiper position for each potentiometer. The
H_ and L_ terminals of the MAX5477/MAX5478/
MAX5479 are similar to the two end terminals of a
mechanical potentiometer. The MAX5477/MAX5478/
MAX5479 feature power-on reset circuitry that loads the
wiper position from the nonvolatile memory at power-up.
256-POSITION
DECODER
H_
L_
R
255
S
255
S
254
S
3
S
2
S
1
S
256
R
254
R
2
R
1
W_
R
W
WIPER
CODE 02h
Figure 2. Potentiometer Configuration
ADDRESS INPUTS
A2 A1 A0
SLAVE ADDRESS
GND GND GND 0101000
GND GND V
DD
0101001
GND V
DD
GND 0101010
GND V
DD
V
DD
0101011
V
DD
GND GND 0101100
V
DD
GND V
DD
0101101
V
DD
V
DD
GND 0101110
V
DD
V
DD
V
DD
0101111
Table 1. Slave Addresses