Datasheet

Detailed Description
The MAX5386/MAX5388 dual, 256-tap, volatile low-
voltage linear taper digital potentiometers offer three end-
toend resistance values of 10kΩ, 50kΩ, and 100kΩ. Each
potentiometer consists of 255 fixed resistors in series
between terminals H and L. The potentiometer wiper, W,
is programmable to access anyone of the 256 tap points
on the resistor string.
The potentiometers in each device are programmable
independently of each other. The MAX5386/MAX5388
have an SPI interface.
SPI Digital Interface
The MAX5386/MAX5388 include an SPI interface, which
provides a 3-wire write-only serial data interface to control
the wiper tap position through inputs chip select (CS),
data in (DIN), and data clock (SCLK). Drive CS low to load
data from DIN synchronously into the serial shift register
on the rising edge of each SCLK pulse. The MAX5386/
MAX5388 load the last 9 bits of clocked data once CS
transitions high. See Figures 2 and 3. After all the data
bits are shifted in, data are latched into the appropriate
potentiometer control register when CS goes from low
to high. Data written to a memory register immediately
updates the wiper position. Keep CS low during the entire
data stream to prevent the data from being terminated.
The first bit A0 (address bit) addresses one of the two
potentiometers; writing a zero in A0 addresses control
register A and writing a one in A0 addresses control reg-
ister B. See Table 1. The power-on reset (POR) circuitry
sets the wiper to midscale (D[7:0] 1000 0000).
The 8 data bits (D7–D0) indicate the position of the wiper.
For D[7:0] = 0000 0000, the wiper moves to the position
closest to L. For D[7:0] = 1111 1111, the wiper moves clos-
est to H. D[7:0] is 1000 0000 following poweron for both
registers A and B.
Register A: The data byte writes to register A, and the
wiper of potentiometer A moves to the appropriate posi-
tion at the rising edge of CS. D[7:0] indicates the position
of the wiper. D[7:0] = 0000 0000 moves the wiper to the
position closest to L. D[7:0] = 1111 1111 moves the wiper
to the position closest to H. D[7:0] is 1000 0000 following
power-on.
Register B: The data byte writes to register B, and the
wiper of potentiometer B moves to the appropriate posi-
tion at the rising edge of CS. D[7:0] indicates the position
of the wiper. D[7:0] = 0000 0000 moves the wiper to the
position closest to L. D[7:0] = 1111 1111 moves the wiper
to the position closest to H. D[7:0] is 1000 0000 following
power-on.
Table 1. SPI Register Map
Bit Number 1 2 3 4 5 6 7 8 9
Bit Name A0 D7 D6 D5 D4 D3 D2 D1 D0
Write Wiper Register A 0 D7 D6 D5 D4 D3 D2 D1 D0
Write Wiper Register B 1 D7 D6 D5 D4 D3 D2 D1 D0
MAX5386/MAX5388 Dual, 256-Tap, Volatile, Low-Voltage
Linear Taper Digital Potentiometers
www.maximintegrated.com
Maxim Integrated │ 8