It is recommended that the user either use six CS puls-
es (convert to a fixed voltage-divider) or five pulses
(program the initial power-up value of the device, but
still be able to adjust the wiper). If the device is pro-
grammed with five pulses and later it is desired to dis-
able the interface (convert to a fixed voltage-divider),
then care must be taken to ensure that the wiper is in
the same position as it was originally set to (when pro-
grammed with five pulses). The full six programming
pulses must be applied. If the wiper is not in its original
programmed position prior to disabling the interface,
the final locked-out position is correct. Note that once
the six-pulse program occurs, no further programming
is possible.
The V
PP
power supply must be able to source at least
5mA and have a good transient response. The V
PP
power
supply should be decoupled with 22µF and have no more
than 250µH of inductance and/or 40Ω of parasitic resis-
tance between the capacitors and the device (Figure 5).
The device does not require decoupling capacitors near
V
PP
, provided the above guidelines are met.
MAX5427/MAX5428/MAX5429
One-Time Programmable, Linear-Taper
Digital Potentiometers
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