CAT5126ZI-50-GT3(2007) 查看數據表（PDF） - Catalyst Semiconductor => Onsemi

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CAT5126ZI-50-GT3
(Rev.:2007)

One-Time Digitally Programmable 32 Tap Potentiometer

Catalyst Semiconductor => Onsemi 

CAT5126

DETAILED DESCRIPTION

The CAT5126 devices are 10kΩ/50kΩ/100kΩ (end-to-

end resistance) digitally controlled potentiometers.

They have 32 tap positions that are accessible to the

wiper along the resistor array between RH and RL.

The wiper (RW) position is adjusted sequentially

through the tap positions using a simple 2-wire

interface. These digital potentiometers have an optional

one-time programmable feature that sets the POR

position of the wiper. The 2-wire interface can then be

disabled, permanently preventing unwanted

adjustment.

DIGITAL INTERFACE OPERATION

The CAT5126 devices have two modes of operation

when the serial interface is active: increment mode

and decrement mode. The serial interface is only

active when C¯¯S¯ is low.

The C¯¯S¯ and U/D¯ inputs control the position of the

wiper along the resistor array. When C¯¯S¯ transitions

from high to low, the part goes into increment mode if

U/D¯ is high (Figure 1), and into decrement mode if

U/D¯ is low (Figure 2). Once the mode is set, the

device remains in that mode until C¯¯S¯ goes high. A

low-to-high transition at the U/D¯ increments or

decrements the wiper position depending on the

current mode.

The value of the counter is then stored and the wiper

position is maintained till the device is Powered down.

The wiper performs a make-before-break transition,

ensuring that there is never an open circuit during a

transition from one resistor tap to another. When the

wiper is at either end (max/min) of the resistor array,

additional transitions in the direction of the endpoint

do not change the counter value (the counter does not

wrap around).

One-Time Programming

The factory-set default position of the wiper on power-

up is tap 16. However, the power-up position can be

changed once using the one-time programming feature.

After the wiper is moved to the desired position, the

programming sequence is initiated by setting U/D¯ high,

applying 10V to VPP, and then taking ¯C¯S¯ low. Five

pulses on ¯C¯S¯ (consisting of ¯C¯S¯ starting from low and

going high for tCH and then low for tCL) program the

device (Figure 3). The programming voltage should

then be taken to zero. After the device is programmed,

VPP can be set to zero or be allowed to float. The wiper

position is still adjustable, but always returns to this

programmed position on power-up.

Figure 1: Increment Mode Serial Interface Timing Diagram

VDD

CS

U/D

VW

tUP

tCU

tCI

tIL

tIH

tIW

Figure 2: Decrement Mode Serial Interface Timing Diagram

VDD

CS

U/D

VW

tUP

tCU

tCI

tIH

tIL

tIW

tIC

tIC

Doc. No. 2129 Rev. A

6

© 2007 Catalyst Semiconductor, Inc.

Characteristics subject to change without notice

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