STC3117 datasheet(18/34 Pages) STMICROELECTRONICS

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Functional description

STC3117

18/34

DocID025792 Rev 2

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

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 VCC 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.

BATD

VCC

CD_drive

1.61 V

Vinmin_cd level

Vin

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