Rainbow Electronics MAX5128 - Manual (Page 10)

MAX5128
Standby Mode
The MAX5128 operates in standby mode while the seri-
al interface is inactive. Programming the MAX5128
increases the average operating current to 400µA
(max). When in standby mode, the static supply current
reduces to less than 0.5µA (typ).
Power-Up
Upon power-up, the MAX5128 updates the wiper posi-
tion with the data stored in the nonvolatile memory. This
initialization period takes 2µs (typ). For proper opera-
tion, limit the supply voltage slew rate to
≥ 10µs.
Applications Information
Use the MAX5128 for applications requiring digitally
controlled adjustable resistance or voltage, such as
LCD contrast control (where voltage biasing adjusts the
display contrast), or DC-DC converters with adjustable
outputs. The 22k
Ω end-to-end resistance is divided into
128 tap points of 172 Ω each. Use the MAX5128 in a
voltage-divider or variable-resistor configuration.
V
COM
Generator
Figure 6 shows an application using the MAX4238 and
the MAX5128 to generate the V
COM voltage for a LCD
panel. Adjusting the resistor value of the MAX5128
changes the V
COM
voltage. Adjusting the V
COM
volt-
age changes the contrast for the LCD panel.
DC-DC Converter Applications
Figures 7 and 8 show two applications using the
MAX5128 to adjust the output voltage of a DC-DC con-
verter. Figure 7 shows the MAX5128 in the grounded
potentiometer configuration. Figure 8 shows the
MAX5128 in a floating potentiometer configuration. The
grounded potentiometer configuration forces the output
voltage range of the DC-DC converter to fall within the
supply voltage range of the MAX5128. Use the floating
potentiometer configuration to allow the DC-DC con-
verter’s output to exceed the supply voltage range of
the MAX5128. The floating potentiometer configuration
increases the output voltage range and increases the
precision of the output voltage adjustment range.
LED Bias Adjustment
Figure 9 shows a LED bias adjustment application
using a MAX5128 to set the current of the LEDs that the
MAX1574 drives. Use the MAX5128 for an adjustable
LED current drive of 10mA to 60mA.
Chip Information
PROCESS: BiCMOS
128-Tap, Nonvolatile, Linear-Taper Digital
Potentiometer in 2mm x 2mm µDFN Package
10 ______________________________________________________________________________________
t IMMU
UP
DN t IMMU t IMMU
t IMMU
PULSES WITH WIDTHS LESS THAN t IMMU ARE IGNORED.
Figure 4. Glitch-Immunity Timing Diagram
MAX5128
IN1
IN2
OUT1
OUT2
GND
V CC
5V
MECHANICAL
SWITCH
UP
DN
H
L
W
V CC
GND
5V
MECHANICAL
SWITCH
V
CC
V
CC
MAX6817
Figure 5. Debouncing the MAX5128’s Digital Inputs