STC3115 Datasheet, PDF (18/31 Pages) STMicroelectronics – Gas gauge IC with alarm output for handheld applications

Functional description
STC3115
6.5
Improving accuracy of the initial OCV measurement with the
advanced functions of BATD/CD and RSTIO/BATD pins
The advanced functions of the BATD/CD and RSTIO/BATD pins provide a way to ensure
that the OCV measurement at power-up is not affected by the application startup or by the
charger operation. This occurs as follows:
• The BATD/CD pin is driven high to V_CC voltage which inhibits the charge function
(assuming that the BATD/CD signal is connected to disable input of the charger circuit).
• The RSTIO/BATD pin senses the system reset state and if the system reset is active
(that is RSTIO/BATD is low), the RSTIO/BATD is kept low until the end of the OCV
measurement.
Figure 10 describes the BATD/CD and RSTIO/BATD operation at power-up. Please refer to
the block diagram of Figure 11 for the RSTI, RSTO, BATD_comp_out, and
BATD_drive_high signals.
At the end of the OCV measurement, the BATD/CD and RSTIO/BATD pin are released
(high impedance), the application can start and the charger is enabled.
Figure 10. BATD and RSTIO timing diagram at power-up
VCC
OCV
meas.
SOC
calc.
delay
Application can start,
charge is enabled
UVLO
POR
BATD_comp_out
1.61V
BATD_drive_high
RSTI
RST0
Voltage
measurement
Voltage
register
SOC register
6.5.1
BATD and RSTIO pins
The STC3115 provides platform synchronization signals to provide reliable SOC information
in different cases.
The BATD/CD pin senses the presence of the battery independently of the battery voltage
and it controls the battery charger to inhibit the charge during the initial OCV measurement.
The RSTIO/BATD pin can be used to delay the platform startup during the first OCV
measurement at battery insertion.
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