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DACPOT™ CookBook - A Collection of Simple and Cost-Effective Applications |
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Download
the entire Applications Note in
PDF format.
Background
The
digitally controlled potentiometer (DCP) is widely
used today as a reliable alternate or replacement
for the mechanical potentiometer
(Figure
1).
The wiper position is 'moved' by enabling one of the transfer gates thereby selecting a single resistor node (including the endpoints, RH and RL) in a manner similar to adjusting the mechanical potentiometer. The DCP may have as few as 3 distinct resistors (4 possible wiper settings) to as many or more than 255 (256 possible wiper settings). Setting of the wiper position is performed digitally via the Control Inputs. The simplest form of control uses an UP/DWN digital input. More sophisticated DCPs use a serial interface such as I2C or SPI. On-board E2PROM is used on more sophisticated units to retain the wiper setting after power-down.
NEXTGEN DCP: " The DACPOT ™ " Like its mechanical counterpart, the DCP suffers in 3 key areas:
To eliminate these shortcomings, Summit's line of DACPOTS™ include a unity gain voltage buffer stage between the wiper and the output pin (Figure 2). The buffer sets the output voltage at each and every tap thereby eliminating end-to-end resistance tolerance and loading of the resistive string.
 Figure 2: Improving the DCP: The DACPOT™
The result is a device that outputs an extremely accurate and temperature stable (± 15ppm/oC) voltage capable of sinking or sourcing current. As an example, Figure 3 displays the S9518 Non-Volatile 256 Position DACPOT™ Block Diagram. Dual and quad 1024 position settings are also available (see the Nonvolatile DACPOT™ Potentiometer Product Summary in Table 1 or on the Summit web site at www.summitmicro.com).
The following list of Figures contain example applications for all of Summit Microelectronics' DACPOT™ product line. Anywhere a programmable resistor or potentiometer is needed, a DACPOT™ can be incorporated to improve noise, accuracy and temperature stability.
SUMMIT Microelectronics, Inc. reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. SUMMIT Microelectronics, Inc. assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained herein reflect representative operating parameters, and may vary depending upon a user's specific application. While the information in this publication has been carefully checked, SUMMIT Microelectronics, Inc. shall not be liable for any damages arising as a result of any error or omission. SUMMIT Microelectronics, Inc. does not recommend the use of any of its products in life support or aviation applications where the failure or malfunction of the product can reasonably be expected to cause any failure of either system or to significantly affect their safety or effectiveness. Products are not authorized for use in such applications unless SUMMIT Microelectronics, Inc. receives written assurances, to its satisfaction, that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; and (c) potential liability of SUMMIT Microelectronics, Inc. is adequately protected under the circumstances.
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