BQ27505-J2 Datasheet, PDF (21/42 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

bq27505-J2
www.ti.com
System-Side Impedance Track™ Fuel Gauge
SLUS924 – APRIL 2009
4.4 ACCESS MODES
The bq27505 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control
data flash access permissions, according to Table 4-6. Data Flash refers to those data flash locations,
specified in Table 4-7, that are accessible to the user. Manufacture Information refers to the three 32-byte
blocks.
Security Mode
FULL ACCESS
UNSEALED
SEALED
Table 4-6. Data Flash Access
Data Flash
R/W
R/W
None
Manufacture Information
R/W
R/W
R(A); R/W(B)
Although FULL ACCESS and UNSEALED modes appear identical, only FULL ACCESS allows the
bq27505 to write access-mode transition keys.
4.5 SEALING/UNSEALING DATA FLASH
The bq27505 implements a key-access scheme to transition between SEALED, UNSEALED, and
FULL-ACCESS modes. Each transition requires that a unique set of two keys be sent to the bq27505 via
the Control( ) control command. The keys must be sent consecutively, with no other data being written to
the Control( ) register in between. Note that to avoid conflict, the keys must be different from the codes
presented in the CNTL DATA column of Table 4-2 subcommands.
When in SEALED mode, the CONTROL_STATUS [SS] bit is set, but when the UNSEAL keys are
correctly received by the bq27505, the [SS] bit is cleared. When the full-access keys are correctly
received, then the CONTROL_STATUS [FAS] bit is cleared.
Both the sets of keys for each level are 2 bytes each in length and are stored in data flash. The UNSEAL
key (stored at Unseal Key 0 and Unseal Key 1) and the FULL-ACCESS key (stored at Full-Access Key
0 and Full-Access Key 1) can only be updated when in FULL-ACCESS mode. The order of the keys is
Key 1 followed by Key 0. The order of the bytes entered through the Control( ) command is the reverse of
what is read from the part. For example, if the Key 1 and Key 0 of the Unseal Keys returns 0x1234 and
0x5678, then the Control( ) should supply 0x3412 and 0x7856 to unseal the part.
4.6 DATA FLASH SUMMARY
Table 4-7 summarizes the data flash locations available to the user, including their default, minimum, and
maximum values.
Class
Configuration
Configuration
Configuration
Configuration
Configuration
Configuration
Configuration
Configuration
Configuration
Configuration
Configuration
Subclass
ID
2
2
2
2
2
2
Subclass
Safety
Safety
Safety
Safety
Safety
Safety
32
Charge Inhibit
Temp Low
32
Charge Inhibit
Temp High
32
Temp
Hysteresis
34
Charge
34
Charge
Table 4-7. Data Flash Summary
Offset
Name
0
OT Chg
2
OT Chg Time
3
OT Chg Recovery
5
OT Dsg
7
OT Dsg Time
8
OT Dsg Recovery
Data
Type
I2
U1
I2
I2
U1
I2
0
Charge Inhibit Temp Low
I2
2
Charge Inhibit Temp High
I2
4
Temp Hys
I2
2
Charging Voltage
I2
4
Delta Temp
I2
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Min
Value
0
0
0
0
0
0
–400
–400
0
0
0
Max
Value
1200
60
1200
1200
60
1200
Default
Value
550
2
500
600
2
550
Units
0.1°C
s
0.1°C
0.1°C
s
0.1°C
1200
0
0.1°C
1200
450
0.1°C
100
50
0.1°C
4600
500
4200
50
mV
0.1°C
GENERAL DESCRIPTION
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