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CAT5126 Folha de dados(PDF) 6 Page - Catalyst Semiconductor

Nome de Peças. CAT5126
descrição  One-Time Digitally Programmable 32 Tap Potentiometer
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Fbricantes  CATALYST [Catalyst Semiconductor]
Página de início  http://www.catalyst-semiconductor.com
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CAT5126 Folha de dados(HTML) 6 Page - Catalyst Semiconductor

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CAT5126
Doc. No. 2129 Rev. A
6
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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 CS
¯¯¯ is low.
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 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 CS
¯¯¯ 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 CS
¯¯¯ low. Five
pulses on CS
¯¯¯ (consisting of CS
¯¯¯ 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
Figure 2: Decrement Mode Serial Interface Timing Diagram
VDD
U/D
CS
VW
tUP
tCU
tCI
tIL
tIH
tIC
tIW
VDD
U/D
CS
VW
tUP
tCU
tCI
tIL
tIH
tIC
tIW


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