BQ27541-V200_1007 Datasheet, PDF (27/43 Pages) Texas Instruments – Single Cell Li-Ion Battery Fuel Gauge for Battery Pack Integration

bq27541-V200
www.ti.com
SLUSA11 – FEBRUARY 2010
DETAILED PIN DESCRIPTIONS
System Shutdown Enable (SE Pin)
By using SE pin, the fuel gauge can be made to power-off through an external circuit. This feature is useful to
shutdown the fuel gauge in a deeply discharged battery to protect the battery.
The following bits are used to configure and control SE pin:
• Two Control Status bits signals the operation of the SE pin:
– SE – bit 15 – Status bit indicating the SE pin is active. Default is 0
– SHUTDOWN – bit 7 – Indicates the shutdown feature is enabled. Default is 0 (disabled)
• Two Control Subcommands enable or disable shutdown functionality:
– SET_SHUTDOWN (0x0013) – enables SE pin functionality (sets SHUTDOWN status bit)
– CLEAR_SHUTDOWN (0x0014) – disables SE pin functionality (clears SHUTDOWN status bit)
• Two Data Flash bits in pack configuration register control the operation of the SE pin:
– SE_PU – low byte bit 3 – Pull-up enable for SE pin when SE pin state is 1
– SE_POL – low byte bit 2 – Polarity for SE pin when shutdown is enabled.
By default the SE pin is in normal state for all modes of operation. By sending SET_SHUTDOWN subcommand
or setting [SE_EN] bit in Pack Configuration Register, the [SHUTDOWN] bit is set and enables shutdown feature.
When this feature is enabled, the SE pin can be in normal state or shutdown state. The shutdown state can only
be entered in HIBERNATE mode, all other modes will default SE pin to normal state. Table 10 shows the SE pin
state for different states.
Note, the bq27541 SE pin will be high impedance at POR, the SE_POL does not affect the state of SE pin at
POR. Also SE_PU configuration change will only take effect after POR.
SE_PU BIT
0
0
1
1
SE_POL BIT
0
1
0
1
Table 11. SE Pin State
SE PIN
IN NORMAL OPERATION
High Impedance
0
1
0
SE PIN STATE
TO SHUTDOWN THE GAUGE
0
High Impedance
0
1
The Pack Configuration Register
Some bq27541 pins are configured via the Pack Configuration data flash register, as indicated in Table 12. This
register is programmed/read via the methods described in Section 1.2.1: Accessing the Data Flash. The register
is located at subclass =64, offset = 0.
High Byte
Low Byte
bit7
RESCAP
–
Table 12. Pack Configuration Bit Definition
bit6
–
RESFACTSTEP
bit5
–
SLEEP
bit4
–
RMFCC
bit3
GNDSEL
SE_PU
bit2
IWAKE
SE_POL
bit1
RSNS1
SE_EN
bit0
RSNS0
TEMPS
RESCAP = No-load rate of compensation is applied to the reserve capacity calculation. True when set. Default is 0.
GNDSEL = The ADC ground select control. The Vss (Pin 6) is selected as ground reference when the bit is clear. Pin 7 is
selected when the bit is set. Default is 0.
IWAKE/RSNS1/RSNS0 = These bits configure the current wake function (see Table 13). Default is 0/0/1.
ResFactStep = Enables Ra step up/down to Max/Min Res Factor before disabling Ra updates. Default is 1
SLEEP = The fuel gauge can enter sleep, if operating conditions allow. True when set. Default is 1.
RMFCC = RM is updated with the value from FCC, on valid charge termination. True when set. Default is 1.
SE_PU = Pull-up enable for SE pin. True when set (push-pull). Default is 0.
SE_POL = Polarity bit for SE pin. SE is active low when clear (makes SE low when gauge is ready for shutdown).
Default is 1 (makes SE high when gauge is ready for shutdown).
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): bq27541-V200
Submit Documentation Feedback
27