BQ2014_15 Datasheet, PDF (15/27 Pages) Texas Instruments – Gas Gauge IC with External Charge Control

Not Recommended For New Designs
bq2014
Reset Register (RST)
The reset register (address=39h) provides the means to
perform a software-controlled reset of the device. By
writing the RST register contents from 00h to 80h, a
bq2014 reset is performed. Setting any bit other than
the most-significant bit of the RST register is not al-
lowed, and results in improper operation of the bq2014.
Resetting the bq2014 sets the following:
n LMD = PFC
n CPI, VDQ, NAC, and NACL = 0
n CI and BRP = 1
Note: Self-discharge is disabled when PROG5 = H.
Display
The bq2014 can directly display capacity information us-
ing low-power LEDs. If LEDs are used, the program
pins should be resistively tied to VCC or VSS for a pro-
gram high or program low, respectively..
The bq2014 displays the battery charge state in relative
mode. In relative mode, the battery charge is repre-
sented as a percentage of the LMD. Each LED segment
represents 20% of the LMD.
The capacity display is also adjusted for the present bat-
tery temperature. The temperature adjustment reflects
the available capacity at a given temperature but does
not affect the NAC register. The temperature adjust-
ments are detailed in the TMPGG register description.
When DISP is tied to VCC, the SEG1–5 outputs are inac-
tive. Note: DISP must be tied to VCC if the LEDs
are not used. When DISP is left floating, the display
becomes active whenever the NAC registers are count-
ing at a rate equivalent to VSRO < -4mV or charge cur-
rent is detected, VSRO > VSRQ. When pulled low, the seg-
ment outputs become active immediately. A capacitor
tied to DISP allows the display to remain active for a
short period of time after activation by a push-button
switch.
The segment outputs are modulated as two banks of
three, with segments 1, 3, and 5 alternating with seg-
ments 2 and 4. The segment outputs are modulated at
approximately 100Hz, with each segment bank active
for 30% of the period.
SEG1 blinks at a 4Hz rate whenever VSB has been de-
tected to be below VEDV1 (EDV1 = 1), indicating a low-
battery condition. VSB below VEDVF (EDVF = 1) disables
the display output.
Microregulator
The bq2014 can operate directly from 3 or 4 cells. To facili-
tate the power supply requirements of the bq2014, an REF
output is provided to regulate an external low-threshold n-
FET. A micropower source for the bq2014 can be inexpen-
sively built using the FET and an external resistor; see
Figure 1.
15