max5402euat Maxim Integrated Products, Inc., max5402euat Datasheet - Page 6

• Manufacturer Part Number: max5402euat
• Description: Max5402 256-tap, ?pot Low-drift, Digital Potentiometer
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5402 consists of 255 fixed resistors in series
between pins H and L. The potentiometer wiper (pin W)
can be programmed to access any one of the 256 dif-
ferent tap points on the resistor string. The MAX5402
has an SPI-compatible 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 8-bit
serial shift register on the rising edge of each SCLK
pulse (Figure 1). The MSB is shifted in first, as shown in
Figure 3. Note that if CS is not kept low during the entire
data stream, the data will be corrupted and the device
256-Tap, µPoT, Low-Drift,
Digital Potentiometer
Figure 1. Serial Interface Timing Diagram
Figure 2. Detailed Serial Interface Timing Diagram
6
_______________________________________________________________________________________
SCLK
CS
DIN
t
CSO
TIME
CS
SCLK
DIN
Detailed Description
t
CSS
t
DS
MSB
t
DH
D7
1ST CLOCK PULSE
D6
t
CL
D5
t
CH
D4
will need to be reloaded. After all 8 data bits have been
loaded into the shift register, they are latched into the
decoder once CS is taken high. The decoder switches
the potentiometer wiper to the tap position that corre-
sponds to the 8-bit input data. Each resistor cell is
10kΩ/255 or 39.2Ω for the MAX5402.
The MAX5402 features POR circuitry. This sets the
wiper to the midscale position at power-up by loading a
binary value of 128 into the 8-bit latch. The MAX5402
can be used as a variable resistor by connecting pin W
to either pin H or L.
D3
D2
8TH CLOCK PULSE
t
CP
D1
LSB
D0
POT REGISTER LOADED
t
CSH
t
CS1
t
CSW