Rainbow Electronics DS1804 User Manual
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DS1804
NV Trimmer Potentiomete
FEATURES
Single 100-position taper potentiometer
Nonvolatile “on-demand” wiper storage
Operates from 3V or 5V supplies
Up/down, increment-controlled interface
Available in 8-pin (300-mil) DIP, 8-pin
(150-mil) SOIC, 8-pin (118-mil) µSOP, and
Flip Chip packages
Operating Temperature:
– Industrial: -40ºC to +85ºC
Standard Resistance Values:
– DS1804-010 10 kΩ
– DS1804-050 50 kΩ
– DS1804-100 100 kΩ
PIN DESCIPTION
H - High-Terminal of Potentiometer
L - Low-Terminal of Potentiometer
W - Wiper of Potentiometer
VCC - 3V or 5V Power Supply
CS - Chip Select
U/ D - Up/Down Control
INC - Increment/Decrement Wiper Control
GND - Ground
PIN ASSIGNMENT
INC 1 8 V
U/D 2 7 CS
H 3 6 L
GND 4 5 W
8-Pin DIP (300-mil)
8-Pin SOIC (150-mil)
8-Pin uSOP (118-mil)
8-Pin Flip Chip Package
See Mech. Drawings Section
CC
DESCRIPTION
The DS1804 NV Trimmer Potentiometer is a nonvolatile digital potentiometer having 100 positions. The
device provides an ideal method for low-cost trimming applications using a CPU or manual control input
with minimal external circuitry. Wiper position of the DS1804 can be stored in EEPROM memory on
demand. The device’s wiper position is manipulated by a 3-terminal port that provides an increment/
decrement counter controlled interface. This port consists of the control inputs CS , INC , and U/ D . The
DS1804 is available in three resistor grades, which include a 10 kΩ, 50 kΩ, and 100 kΩ. The device is
provided in an industrial temperature grade. Additionally, the DS1804 will operate from 3V or 5V
supplies and is ideal for portable application requirements. Three packaging options are available and
include the 8-pin (300-mil) DIP, 8-pin (150-mil) SOIC, 8-pin (118-mil) uSOP, and the Flip Chip
Package.
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DS1804
OPERATION
The DS1804 is a single nonvolatile potentiometer. The device has a total of 100 tap-points including the
L- and H- terminals. A total of 99 resistive segments exist between the L- and H- terminals. These tappoints are accessible to the W-terminal, whose position is controlled via a 3-terminal control port. A
block diagram of the DS1804 is shown in Figure 1.
The 3-terminal port of the DS1804 provides an increment/decrement interface which is activated via a
chip select input. This interface consists of the input signals CS , INC , and U/ D . These input signals
control a 7-bit up/down counter. The output of the 7-bit up/down counter controls a 1 of 100 decoder to
select wiper position. Additionally, this interface provides for a wiper storage operation using the CS and
INC input control pins. The timing diagram for the 3-terminal interface control is shown in Figure 2.
PIN DESCRIPTIONS
VCC - Power Supply. The DS1804 will support supply voltages ranging from +2.7 to +5.5 volts.
GND - Ground.
H - High-Terminal Potentiometer. This is the high terminal of the potentiometer. It is not required that
this terminal be connected to a potential greater than the L-terminal. Voltage applied to the H-terminal
can not exceed the power-supply voltage, V
, or go below ground.
CC
L - Low-Terminal Potentiometer. This is the low terminal of the potentiometer. It is not required that this
terminal be connected to a potential less than the H-terminal. Voltage applied to the L-terminal cannot
exceed the power-supply voltage, VCC, or go below ground.
W - Wiper of the Potentiometer. This pin is the wiper of the potentiometer. Its position on the resistor
array is controlled by the 3-terminal control port. Voltage applied to the wiper cannot exceed the powersupply voltage, VCC, or go below ground.
CS - Chip Select. The CS input is used to activate the control port of the DS1804. This input is active
low. When in a high-state, activity on the INC and U/ D port pins will not affect or change wiper
position.
INC - Wiper Movement Control. This input provides for wiper position changes when the CS pin is low.
Wiper position changes of the W-terminal will occur one position per high-to-low transition of this input
signal. Position changes will not occur if the CS pin is in a high state.
U/ D - Up/Down Control. This input sets the direction of wiper movement. When in a high state and CS
is low, any high-to-low transition on INC will cause a one position movement of the wiper towards the
H-terminal. When in a low state and CS is low, any high-to-low transitions on INC will cause the
position of the wiper to move towards the L-terminal.
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DS1804 BLOCK DIAGRAM Figure 1
POWER-UP/POWER-DOWN CONDITIONS
On power-up the DS1804 will load the value of EEPROM memory into the wiper position register (or 1
of 100 decoder). The value of this register can then be set to another wiper position if desired, by using
the 3-terminal control port. On power-up, wiper position will be loaded within a maximum time period of
500 µs once the power-supply is stable. Additionally, the 3-terminal interface port will be active after 50
ms.
On power-down, the wiper position register data will be lost. On the next device power-up, the value of
EEPROM memory will be loaded into the wiper position register.
On shipment from the factory, Dallas Semiconductor does not guarantee a specified EEPROM memory
value. This value should be set by the customer as needed.
NONVOLATILE WIPER STORAGE
Wiper position of the DS1804 can be stored using the INC and CS inputs. Storage of the wiper position
takes place, whenever the CS input transitions from low-to-high while the INC is high. Once this
condition has occurred the value of the current wiper position will be written to EEPROM memory.
The DS1804 is specified to accept 50,000 writes to EEPROM before a wear-out condition. After wear-out
the DS1804 will still function and wiper position can be changed during powered conditions using the 3terminal control port. However, on power-up the wiper-position will be indeterminate.
ONE TIME PROGRAMMABILITY (OTP)
The DS1804 can be easily used as an OTP device. The user of the DS1804 can trim the desired value of
the wiper position and set this position for storage as described above. Any activity through the 3-
terminal port can then be prevented by connecting the CS input pin to VCC. Also, an OTP application
does not adversely affect the number of times EEPROM is written, since EEPROM will only be loaded
and not written during a power-up or power-down condition.
On power-up the DS1804 will load the current value of EEPROM memory into the wiper position
register.
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