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DS1809-010-DS1809U-010-DS1809U-050-DS1809U-100-DS1809Z-010
Dallastat, 64-position linear taper
FEATURES 64-position linear taper Two nonvolatile wiper storage options§ Operates from +2.7 to +5.5-volt supplies Operating Temperature Range:
- Industrial: -40°C to +85°C Electronic interface provides either digital or
pushbutton control§ Low-cost alternative to mechanical solutions Standard Resistance Values
- DS1809-01010 kW
- DS1809-05050 kW
- DS1809-100100 kW
PIN DESCIPTIONVCC-Supply Voltage
RH - High End of Resistor
RL - Low End of Resistor
RW - Wiper TerminalUC - Up Control Input
DC - Down Control Input
STR - Storage Enable Input
GND-Ground
PIN ASSIGNMENT
DESCRIPTIONThe DS1809 Dallastat is a nonvolatile digitally controlled potentiometer that provides 64 uniform wiper
positions over the entire resistor range; including the high-end and low-end terminals of the device. The
DS1809 is a low power, low voltage device capable of operating from power supplies of +2.7V to +5.5V.
The device is ideal for low-power, portable, or battery powered applications.
Wiper position is maintained in the absence of power. This is accomplished via the use of an EEPROM
cell array. The device provides for two storage methods, which include an auto-store capability and a
command-initiated storage function. The EEPROM cell array is specified to accept greater than 50kwrites. Storage of the wiper position is discussed in the Wiper Storage section of this datasheet.
Wiper positioning is controlled via a patented dual pushbutton (or contact closure) interface. For simple
pushbutton-controlled applications or CPU-generated control signals, external debounce circuitry is not
needed. The control interface will support both repetitive pulse inputs and continuous pulse (“push-and-
Dallastat
DS1809
The DS1809 is available in standard 10 kW, 50 kW, and 100 kW resistor versions. The DS1809 is
provided as an industrial temperature grade part only. Available packaging for the DS1809 include an 8-
lead (300-mil) DIP an 8-lead (150-mil) SOIC, and an 8-lead (118-mil) mSOP.
BLOCK DIAGRAM Figure 1
OPERATIONThe DS1809 Dallastat is a digitally controlled, nonvolatile potentiometer. A block diagram of the
DS1809 is shown in Figure 1. The DS1809 is a linear potentiometer providing 64-uniform wiper
positions over the entire resistor range including the end-terminals. All three potentiometer terminals of
the device are accessible. These terminals include RH, RL, and RW. RH and RL are the end-terminals of the
potentiometer. These terminals will have a constant resistance between them as defined by the
potentiometer value chosen: 10 kW, 50 kW, or the 100 kW version. Functionally, RH and RL are
interchangeable. The wiper terminal, RW, is the multiplexed terminal and can be set to one of the 64 total
positions that exist on the resistor ladder including the RH and RL terminals.
Control of the wiper (RW) position setting is accomplished via the two inputs UC and DC. The UC andDC control inputs, when active, determine the direction on the resistor array that the wiper position will
move. The UC (up control) control input is used to move the wiper position towards the RH terminal. The
DC (down control) control input is used to move wiper position towards the RL terminal.
The control inputs UC and DC are active low inputs which interpret input pulse widths as the means of
controlling wiper movement. Internally, these inputs are pulled up to VCC via a 100 kW resistance. A
transition from a high-to-low on these inputs is considered the beginning of pulse input activity.
A single pulse on the UC or DC input is defined as being greater than 1 millisecond but lasting no longer
that ½ second. This type pulse input will cause the wiper position of the Dallastat to move one position.
Multiple pulse inputs (repetitive pulse inputs) can be used to step through each wiper position of the
device. The requirement for a repetitive pulse train on the UC or DC inputs is that pulses must be
separated by a minimum high time of 1 millisecond. If this is not the case the Dallastat will ignore that
pulse input.
DS1809
A continuous pulse input (“push and hold”) is defined as lasting longer that ½ second. A continuous pulse
input will cause the wiper position to move one position every 100 milliseconds following the initial ½-
second hold time. The total time to transcend the entire potentiometer given a continuous pulse input is
provided by the equation:
½(second) + 62 X 100 ms = 6.7 (seconds)
If the wiper position of the DS1809 is incremented to an end-position, it will stay at that position until the
device receives an opposite direction input pulse command over the UC or DC inputs. For example, if the
wiper position is incremented to the RH terminal using the UC input control, it will stay at that positionuntil UC is first deactivated, and then the DC input is activated to move the wiper position towards the RL
terminal.
The UC and DC control inputs are designed to support simple pushbutton inputs or CPU generated
inputs. Figure 2 illustrates the requirements for pushbutton generated controls. For manual pushbuttoncontrols all that is required are the desired pushbuttons to implement contact closure. No external
debounce or timing circuitry is needed to support the pushbutton operation.
Applications using CPU generated controls must power the UC and DC control pins in a high state to
avoid any inadvertent wiper position movement. To help prevent inadvertent wiper position movementduring a power-up, the DS1809 locks out the control port inputs for a minimum time of 10 ms.
WIPER STORAGEAs stated earlier, the DS1809 provides for two methods of nonvolatile wiper storage using internal
EEPROM memory cells. These two methods include an autostore configuration and a command initiated
storage operation, both of which utilize the STR input pin. The EEPROM cell array of the DS1809 isdesigned to accept greater than 50k writes.
AutostorageThe autostore configuration is designed to provide wiper position storage as the part powers down;
writing the current wiper position into memory. The configuration for initiating the automatic storage
capability of the DS1809 is shown in Figure 3. As shown in this configuration, two external devices are
required to insure proper wiper storage. This includes a Schottky diode and a 10-uf capacitor. Theautomatic store configuration will cause the DS1809 to initiate storage of wiper position when power
(VCC) to the device is removed. The 10-uF capacitor and Schottky diode are used to provide supplemental
power for wiper storage.
Command-Initiated Wiper StorageThe DS1809 will also support a command-initiated wiper storage operation during powered conditions.
For command initiated storage the STR pin should be held in a low state on power-up; otherwise the part
will assume an autostore configuration. As shown in Figure 5, a low-to-high pulse lasting at least 1 ms onthe STR input will cause the DS1809 to initiate the storage of the current wiper position into EEPROM
when VCC is present.
DS1809
PUSHBUTTON CONFIGURATION Figure 2It is assumed that the STR input will be controlled by either external logic or CPU driven. No external
capacitors or diodes are needed for the command-initiated storage operation.
The STR input will take precedence over the pushbutton inputs UC and DC.
AUTOSTORE CONFIGURATION Figure 3
PUSHBUTTON TIMING DIAGRAMS Figure 4
DS1809
If during any pushbutton activity the STR input is activated, pushbutton operation will be suspended until
the storage of EEPROM has been completed. Once complete, pushbutton inputs, if still active, will
resume from the point of suspension. Command initiated storage operations will require a minimum of 4
ms to complete the storage operation. This 4 ms is measured from the rise of STR input (see Figure 5).
For applications not requiring or using the nonvolatile memory feature of the DS1809, it is recommendedthat the STR input be connected to GND.
COMMAND INITIATED WIPER STORAGE - Figure 5
DS1809
ABSOLUTE MAXIMUM RATINGS*Voltage on Any Pin Relative to Ground-1.0V to +7.0VOperating Temperature-40°C to +85°C; industrial
Storage Temperature-55°C to +125°C
Soldering Temperature260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or any other conditions above
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS (-40°C to +85°C)
DC ELECTRICAL CONDITIONS(-40°C to +85°C)
