MAX5429 Maxim Integrated Products, MAX5429 Datasheet - Page 6

• Manufacturer Part Number: MAX5429
• Description: (MAX5427 - MAX5429) Linear-Taper Digital Potentiometers
• Manufacturer: Maxim Integrated Products

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The value of the counter is then stored and the wiper
position is maintained.
The wiper performs a make-before-break transition,
ensuring that there is never an open circuit during a tran-
sition 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).
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 fea-
ture. After the wiper is moved to the desired position,
the programming sequence is initiated by setting U/D
high, applying 11V to V
pulses on CS (consisting of CS starting from low and
going high for t
device (Figure 4). The programming voltage should
then be taken to zero. After the device is programmed,
V
position is still adjustable, but always returns to this
programmed position on power-up.
One-Time Programmable, Linear-Taper
Digital Potentiometers
Figure 2. Increment Mode Serial Interface Timing Diagram
Figure 3. Decrement Mode Serial Interface Timing Diagram
6
PP
_______________________________________________________________________________________
can be set to zero or be allowed to float. The wiper
V
U/D
CS
V
DD
W
V
U/D
CS
V
DD
W
CH
and then low for t
PP
One-Time Programming
, and then taking CS low. Five
t
UP
t
UP
t
CU
t
CU
CL
t
) program the
CI
t
CI
t
IW
t
IH
t
IL
If the intent is to program the device to a specific wiper
position and not to allow further adjustments, then six
programming pulses are required (as opposed to five),
as shown in Figure 4. The sixth pulse locks the wiper
position and disables the serial interface. This also
allows U/D and CS to float without any increase in sup-
ply current. Once the lockout bit is set, no further
adjustment to the potentiometer is possible, effectively
changing the potentiometer into a fixed resistor-divider
(Table 1).
Table 1. One-Time Programming Options
Factory Default
(Unprogrammed)
Programmed
(5 Programming Pulses)
Lock-Bit Set
(6 Programming Pulses)
t
IW
MODE
t
IL
t
IH
RESET WIPER
Programmed
Programmed
POWER-ON
t
POSITION
IC
position
position
Tap 16
t
IC
ADJUSTABLE
WIPER
Yes
Yes
No
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