AN2865 datasheet(14/17 Pages) STMICROELECTRONICS

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Software detection and hardware detection

AN2865

14/17

Doc ID 15283 Rev 1

Software detection and hardware detection

If the battery voltage is not high enough to wake up the application controller but is higher

than 2.2 V, the STUSBCD01B can perform an automatic detection to allow the user to start

charging the battery and make its voltage reach a value which will wake up the ASIC. This

automatic detection is called hardware detection while the ASIC controlled detection is

referred to as software detection.

When the ASIC wakes up, the result of the hardware detection is available until the

STUSBCD01B is reset.

The hardware detection mode is automatically entered when the VIO voltage is not available.

In this mode of operation all VIO referred inputs are ignored and the detection method is set

using the default method pin as described in Table 1 on page 5.

As in the software detection mode, the start of the detection process is triggered by the

VBUS voltage going high. If the detection fails but the VBUS voltage is still present, a new

detection is performed once per second in an infinite loop as shown in the simplified

flowchart in figure 9. This periodic detection is stopped only if:

– the detection result is positive;

–the VBUS voltage drops under the VTH_VBUS threshold;

–the VIO voltage goes high.

Figure 9.

HW/SW detection flowchart

BUS goes

HIGH

Is V

IO High?

detection

Yes

End

detection

Is DET(*)

High?

Yes

End

Start

1s timer

Yes

Timer expired

Or V

IO high?

Yes

(*) DET = Detect. High if charger detected

BUS goes

HIGH

Is V

IO High?

detection

Yes

End

detection

Is DET(*)

High?

Yes

End

Start

1s timer

Yes

Timer expired

Or V

IO high?

Yes

(*) DET = Detect. High if charger detected

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