ds2786 Maxim Integrated Products, Inc., ds2786 Datasheet - Page 15

• Manufacturer Part Number: ds2786
• Description: Ds2786 Standalone Ocv-based Fuel Gauge
• Manufacturer: Maxim Integrated Products, Inc.

DS2786 Standalone OCV-Based Fuel Gauge
The Learn Delta Percent Threshold allows the application to select how large of a cell capacity change is required
before the new cell capacity value is learned. The difference between the present OCV measurement and the Last
OCV measurement must be greater than the Learn Delta Percent Threshold value for a Learn to occur. This
prevents IC measurement resolution from adding error to the Learned Cell Capacity value. It is recommended this
register be set to a value of at least 50%.
Figure 20. Learn Delta Percent Threshold
Address 7Eh
7
6
5
4
3
2
1
0
2
2
2
2
2
2
2
2
MSb
LSb
Units: 0.5%
MEMORY MAP
The DS2786 has memory space with registers for instrumentation, status, and control. When the MSB of a two-
byte register is read, both the MSB and LSB are latched and held for the duration of the read data command to
prevent updates during the read and ensure synchronization between the two register bytes. For consistent results,
always read the MSB and the LSB of a two-byte register during the same read data command sequence.
Memory locations 60h through 7Fh are EEPROM storage locations. EEPROM memory is shadowed by RAM to
eliminate programming delays between writes and to allow the data to be verified by the host system before being
copied to EEPROM. The Read Data and Write Data protocols to/from EEPROM memory addresses access the
shadow RAM. Setting the RCALL bit in the Command Register (FEh) initiate data transfer from the EEPROM to the
shadow RAM.
Setting the COPY bit in the Command Register initiates data transfer from the shadow RAM to the EEPROM. An
external voltage supply must be provided on the VPROG pin prior to writing the COPY bit. The DS2786 requires
the COPY bit be reset to 0 within the t
time window to properly program EEPROM. Resetting COPY too soon
PROG
may prevent a proper write of the cells. Resetting COPY too late may degrade EEPROM Copy Endurance.
The DS2786 uses shadow RAM data for fuel gauge calculations. Fuel gauge information can be changed in the
application by writing the shadow RAM locations. Afterwards the SOCV bit should be written to reset the fuel
gauge. Note that any reset of the I.C. will cause the Shadow RAM data to be restored from EEPROM.
Figure 21. EEPROM Access via Shadow RAM
Copy
EEPROM
Write
Recall
Serial
Shadow RAM
Read
Interface
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