DS1804
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 3-
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 3-
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.
3 of 7
102699
DALLAS [ DALLAS SEMICONDUCTOR ]
