STC3117 Datasheet, PDF (18/34 Pages) STMicroelectronics – Gas gauge IC with battery charger control for handheld applications

Functional description
STC3117
6.5
Power-up and battery swap detection
When the STC3117 is powered up at first battery insertion (power-on reset) or after a soft
reset condition (PORDET bit set by host), an automatic battery voltage, current and
temperature measurement cycle is made immediately after startup and debounce delay.
This feature enables the system controller to get the SOC of a newly inserted battery based
on the OCV.
The CD pin controls the battery charger to inhibit the charge during the initial OCV
measurement. The CD output is validated during the power-up/restart sequence but is
actually driven high only if the battery is present (BATD < 1.61V) and the battery voltage is
higher than a threshold (Vin > Vinmin_cd) at the beginning of the restart sequence.
The CD pin can be driven high under software control by using the bit FORCE_CD in the
REG_MODE register.
The BATD pin senses the presence of the battery independently of the battery voltage.
Figure 8. BATD and CD internal architecture overview
V_CC
&
CD
CD_drive
+
Vin
-
Vinmin_cd level
BATD
+
1.61 V -
The BATD pin is an analog I/O. The input detection threshold is typically 1.61 V.
The CD pin is an output connected to the V_CC level when active. Otherwise, it is high
impedance.
The BATD pin can be connected to the NTC sensor or to the identification resistor of the
battery pack. By default, the STC3117 provides an internal pull-up resistor for the detection
of battery removal. The internal resistor can be disabled by clearing the bit BATD_PU in the
REG_MODE register. When disabled, an external pull-up resistor or another device has to
pull the BATD pin high.
18/34
DocID025792 Rev 2