CAT5122 CATALYST [Catalyst Semiconductor], CAT5122 Datasheet - Page 4

• Manufacturer Part Number: CAT5122
• Description: 16-Tap MiniPot TM Digitally Programmable Potentiometers with 2-Wire Interface
• Manufacturer: CATALYST [Catalyst Semiconductor]

CAT5120, CAT5121, CAT5122
FunCTIOnAl DesCrIPTIOn
The CAT5120/5121/5122 consist of a fixed resistor
and a wiper contact with 6-tap points that are digitally
controlled through a 2-wire up/down serial interface.
Three end-to-end resistance values are available: 10kΩ,
50kΩ and 100kΩ.
The CAT520 is designed to operate as a potentiometer.
In this configuration, the low terminal of the resistor array
is connected to ground (pin 2).
The CAT522 performs as a variable resistor. In this
device, the wiper terminal and high terminal of the
resistor array is connected at pin 5. The CAT52 is
a similar variable resistor, except the low terminal is
connected to pin 5.
DIGITAl InTerFACe OPerATIOn
The Minipots have two modes of operation when the
serial interface is active: increment and decrement mode.
The serial interface is only active when CS is low.
Figure 1. serial Interface Timing Diagram, Increment Mode
Figure 2. serial Interface Timing Diagram, Decrement Mode
Doc. No. 22, Rev. C
CS
U/D
W
Note: "W" is not a digital signal. It represents wiper transitions.
CS
U/D
W
Note: "W" is not a digital signal. It represents wiper transitions.
t
CU
t
CU
t
CI
t
SETTLE
t
CI
t
SETTLE
t
IL
t
IH
4
The CS and U/D inputs control the position of the wiper
along the resistor array. When CS transitions from high
to low, the part will go into increment mode if U/D input
is high, and into decrement mode when U/D input is low.
Once the mode is set, the device will remain in that mode
until CS goes high again. A low-to-high transition at the
U/D pin will increment or decrement the wiper position
depending on the current mode (Figures  and 2).
When the CS input transitions to high (serial interface
inactive), the value of the counter is stored and the wiper
position is maintained.
Note that when the wiper reaches the maximum (or
minimum) tap position, the wiper will not wrap around
to the minimum (or maximum) position.
POWer-On reseT
All parts in this family feature power-on reset (POR)
circuitry that sets the wiper position to midscale at power-
up. By default, the chip is in the increment mode.
t
IH
t
IL
t
SETTLE
Characteristics subject to change without notice
© 2007 by Catalyst Semiconductor, Inc.
t
IC
t
SETTLE
t
IC