DS1804_11 Datasheet, PDF (3/10 Pages) Maxim Integrated Products – Nonvolatile Trimmer Potentiometer Operates from 3V or 5V Supplies

DS1804 BLOCK DIAGRAM Figure 1
DS1804
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 three-terminal control port. On power-up, wiper position will be loaded within a maximum time
period of 500µs once the power-supply is stable. Additionally, the three-terminal interface port will be
active after 50ms.
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, Maxim Integrated Products 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 over 0°C to 70ºC before a wear-out
condition. After wear-out the DS1804 will still function and wiper position can be changed during
powered conditions using the three-terminal 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 three-
terminal port can then be prevented by connecting the CS input pin to V_CC. 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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