max5528 Maxim Integrated Products, Inc., max5528 Datasheet - Page 9

• Manufacturer Part Number: max5528
• Description: 64-tap, One-time Programmable, Linear-taper Digital Potentiometers
• Manufacturer: Maxim Integrated Products, Inc.

Figure 5. One-Time Program Mode, Serial-Interface Timing Diagram
Table
Change the wiper’s power-up position using the PV
one-time programming sequence after power-up (see
Figure 5). After setting the wiper to the desired power-
up position, perform the following six-step sequence:
1)
2)
3)
4a)
4b)
5)
6)
Factory Default
(Unprogrammed)
Programmed by
Six CS Pulses
Programmed by
Seven CS Pulses
U/D
CS
PV
+11V
0V
One-Time Programmable, Linear-Taper Digital
Set U/D and CS high.
Connect an external voltage source at PV in the
range of +11V to +11.55V.
Pull CS low.
Pulse CS high for six cycles, consisting of CS
starting low and going high for at least t
then low for at least t
power-up position. The wiper remains adjustable.
Pulse CS high for seven cycles, consisting of CS
starting low and going high for at least t
low for at least t
position and lock the wiper in that same position.
The seventh CS pulse is labeled the optional lock-
out bit in Figure 5.
Connect PV to GND or release the voltage source,
leaving PV floating.
Pull CS high.
MODE
1. One-Time Programming Options
_______________________________________________________________________________________
t
Programmed position
Programmed position
PC
POWER-ON RESET
WIPER POSITION
CL
, to change the wiper power-up
Tap 31
CL
t
CH
, to change the wiper
ADJUSTABLE
CH
6 PULSES RECORD WIPER POSITION
t
WIPER
CL
Yes
Yes
No
and then
CH,
and
Pulse CS high for six cycles to change the wiper power-
up position. The wiper position returns to this pro-
grammed position on power-up, but remains adjustable.
Pulse CS high for seven cycles to lock the MAX5527/
MAX5528/MAX5529 to a specific wiper position with no
further adjustments allowed. This effectively converts
the potentiometer to a fixed resistor-divider. The sev-
enth pulse locks the wiper position and disables the
up/down interface. Once locked, connect U/D and CS
high, low, or leave them floating without increasing the
supply current (see Table 1).
The external PV power supply must source at least 5mA
and have a good transient response. Decouple the PV
power supply with a 22µF capacitor to GND. Ensure that
no more than 250µH of inductance and/or 40Ω of para-
sitic resistance exists between the capacitor and the
device (see Figure 6).
Figure 6. PV Power-Supply Decoupling
11V
22µF
Potentiometers
L
< 250µH
PARASITIC
TRACE PARASITICS
R
OPTIONAL 7TH
PARASITIC
LOCKOUT BIT
< 40Ω
t
CP
PV
t
PH
MAX5527
MAX5528
MAX5529
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