CAT5251

© Catalyst Semiconductor, Inc.

3

Doc. No. MD-2017 Rev. F

Characteristics subject to change without notice

SERIAL BUS PROTOCOL

The

CAT5251

supports

the

SPI

bus

data

transmission protocol. The synchronous Serial

Peripheral Interface (SPI) helps the CAT5251 to

interface directly with many of today's popular

microcontrollers. The CAT5251 contains an 8-bit

instruction register. The instruction set and the

operation codes are detailed in Table 3, Instruction

Set on page 8.

After the device is selected with CS

¯¯¯ going low the

first byte will be received. The part is accessed via

the SI pin, with data being clocked in on the rising

edge of SCK. The first byte contains one of the six

op-codes that define the operation to be performed.

DEVICE OPERATION

The CAT5251 is four resistor arrays integrated with an

SPI serial interface logic, four 8-bit wiper control

registers and sixteen 8-bit, non-volatile memory data

registers. Each resistor array contains 255 separate

resistive elements connected in series. The physical

ends of each array are equivalent to the fixed terminals

are symmetrical and may be interchanged. The tap

positions between and at the ends of the series

resistors are connected to the output wiper terminals

for each potentiometer is connected to its wiper terminal

at a time and is determined by the value of the wiper

control register. Data can be read or written to the wiper

control registers or the non-volatile memory data

registers via the SPI bus. Additional instructions allow

data to be transferred between the wiper control

registers and each respective potentiometer's non-

volatile data registers. Also, the device can be

instructed to operate in an "increment/decrement"

mode.

ABSOLUTE MAXIMUM RATINGS (1)

Parameter

Ratings

Units

Temperature Under Bias

-55 to +125

°C

Storage Temperature

-65 to +150

°C

(2)(3)

V

-2.0 to +7.0

V

1.0

W

Lead Soldering Temperature (10 secs)

300

°C

Wiper Current

±6

mA

Recommended Operating Conditions

Notes:

(1) Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings

only, and functional operation of the device at these or any other conditions outside of those listed in the operational sections of this

specification is not implied. Exposure to any absolute maximum rating for extended periods may affect device performance and reliability.

(2) The minimum DC input voltage is –0.5V. During transitions, inputs may undershoot to –2.0V for periods of less than 20ns. Maximum DC

Parameter

Ratings

Units

Operating Ambient Temperature (Industrial)

-40 to +85

°C