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STC3117

Functional description

34

Figure 9. Timing diagram details of the power-up and restart sequence

Battery swap detection

A battery swap can be detected in two ways:

•

the battery voltage drops below the undervoltage lockout (UVLO) for more than tdel

•

the BATD signal rises above the BATD threshold (1.61 V typ) for more than tdel

The tdel delay is 0.5 s.

Using the 0.5 s filter provides robust battery swap detection and prevents false battery swap

detection if short contact bouncing occurs at the battery terminals due to mechanical

vibrations or shocks. This also prevents false detections in case of short battery voltage

drops and protects the application against high surge currents at low temperatures.

Following a battery swap detection and after the battery voltage goes back above UVLO

and the BATD level returns to low level, the STC3117 is on hold with new voltage and

current measurements in the corresponding registers. The system has to restart the

STC3117 by doing a device soft reset i.e. by setting the PORDET bit to 1 in the REG_CTRL

register and restoring the parameters (if needed). To recover the event, either use the

measured voltage and current to define a new OCV voltage, or restore a previous SOC

state.

The occurrence of the battery swap event is indicated by the BATFAIL and UVLOD bits in

the REG_CTRL register.

VCC

UVLO

Internal 1mA

sink current

Voltage

measurement

delay

CD pin

(low means HiZ)

OCV

meas.

Application can start,

charge is enabled

Current

measurement

Temperature

measurement

125

ms

Conversion

counter

X

0

1

23

Vinmin_cd

Ibat

meas.

(arbitrary Vcc

waveforms only to

illustrate the function)

“Dead”

battery

“Good”

battery

GAMS1601141520CB

“Good” battery

“Dead” battery

375 ms

125

ms

125

ms

250

ms

100

ms