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Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 4291
Maxim > Design Support > Technical Documents > Application Notes > General Engineering Topics > APP 4291
Maxim > Design Support > Technical Documents > Application Notes > Signal Generation Circuits > APP 4291
Keywords: Initial, accuracy, digital, pots, potentiometer, end-to-end, tolerance, resistance, voltage,
dividers, ratiometric, ratio, steps, LSB, taps, error, temperature, coefficient, series, resistor, noise,
change, reference, buffer, amplifier, NPN, PNP, low, pass
APPLICATION NOTE 4291
Stack References for Higher Adjustable Voltages
from a Digital Pot
By: Bill Laumeister, Strategic Applications Engineer
Sep 24, 2008
Abstract: This application note presents three designs that use references with digital potentiometers to
adjust voltages. As the designs increase in complexity and number of references, the voltage can be
adjusted even higher. The MAX5436 family of digital pots serves as the example devices.
Introduction
There are ways to create a 30V adjustable voltage from a digital potentiometer that is limited to a 5V
power-supply range. The easiest methods use a member of the MAX5436 digital pot family. Featuring
digital logic-control voltages, which are independent of the pot voltages, these digital pots can withstand
more than plus or minus 30V.
This application note discusses how to reduce step voltage, increase accuracy, and improve temperature
performance with a digital pot. A circuit using any digital pot without the special MAX5436 high-voltage
capability is shown. This allows existing digital pots with up to 1024 taps to produce a voltage higher
than their original specified power-supply voltage.
The Easy Way
Figure 1 shows a simple way to create a 30V adjustable voltage. The control voltages (2.7V to 5V) of
the MAX5436–MAX5439 digital pots are independent of the pot voltages (+10V to +30V and -28V to -
10V. or ±5V to ±15V).
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