MAX5487 MAXIM [Maxim Integrated Products], MAX5487 Datasheet - Page 10

• Manufacturer Part Number: MAX5487
• Description: Dual, 256-Tap, Nonvolatile, SPI-Interface, Linear-Taper Digital Potentiometers
• Manufacturer: MAXIM [Maxim Integrated Products]

This command may affect one potentiometer at a time,
or both simultaneously, depending on the state of A1
and A0. Alternatively, the “write NV register” command
can be used to store the current position of the wiper to
the NV register.
This command (C1, C0 = 11) restores the wiper position
to the previously stored position in the NV register. This
command may affect one potentiometer at a time, or both
simultaneously, depending on the state of A1 and A0.
The internal EEPROM consists of a nonvolatile register
that retains the last stored value prior to power-down.
The nonvolatile register is programmed to midscale at
the factory. The nonvolatile memory is guaranteed for
200,000 wiper write cycles and 50 years for wiper data
retention.
Upon power-up, the MAX5487/MAX5488/MAX5489
load the data stored in the nonvolatile wiper register
into the volatile memory register, updating the wiper
position with the data stored in the nonvolatile wiper
register. This initialization period takes 5µs.
Dual, 256-Tap, Nonvolatile, SPI-Interface,
Linear-Taper Digital Potentiometers
Figure 3. Digital-Interface Format
10
Copy NV Register to Wiper Register (Command 11)
B) 8-BIT COMMAND WORD
A) 16-BIT COMMAND/DATA WORD
______________________________________________________________________________________
SCLK
SCLK
DIN
DIN
CS
CS
1
1
2
2
C1
3
C1
3
Nonvolatile Memory
C0
4
C0
4
5
5
Power-Up
6
6
7
7
A1
A1
8
8
A0
A0
The MAX5487/MAX5488/MAX5489 feature a low-power
standby mode. When the device is not being pro-
grammed, it enters into standby mode and supply cur-
rent drops to 0.5µA (typ).
The MAX5487/MAX5488/MAX5489 are ideal for circuits
requiring digitally controlled adjustable resistance,
such as LCD contrast control (where voltage biasing
adjusts the display contrast), or for programmable fil-
ters with adjustable gain and/or cutoff frequency.
Figures 4 and 5 show an application where the
MAX5487/MAX5488/MAX5489 provide an adjustable,
positive LCD-bias voltage. The op amp provides buffer-
ing and gain to the resistor-divider network made by
the potentiometer (Figure 4) or by a fixed resistor and a
variable resistor (Figure 5).
Figure 6 shows the MAX5487/MAX5488/MAX5489 in a
1st-order programmable-filter application. Adjust the gain
of the filter with R
9
D7
10
D6
11
D5
Applications Information
2
, and set the cutoff frequency with R
12
D4
Positive LCD Bias Control
13
D3
Programmable Filter
14
D2
15
D1
16
D0
Standby
3
.