STCC5021 datasheet(17/37 Pages) STMICROELECTRONICS

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STCC5011, STCC5021

Application information

Figure 6. Attach and charging detection - Timing diagram

5.6

Charging detection and safety timer

The STCC5011-STCC5021 devices continuously monitor current drawn by the portable

device. While programmed in CDP or DCP mode, the STCC5011-STCC5021 devices send

a charging flag to the system if the current through the USB power switch is above the

charging threshold, set at 20 mA typ.: open drain active low output CHARGING/ATTACH is

asserted.

Note:

In CDP mode the charging flag is asserted only if the CDP handshaking between the

portable device and the host is performed before the current is above threshold.

If the CHARGING/ATTACH output is already asserted because of attachment detection

(while the host is in S4/S5 states or G3 state), this output stays unchanged.

For systems in S5 providing current charge while being battery supplied, there is a safety

timer integrated into the STCC5011-STCC5021 devices. This timer is started only after an

attach event with input ATTACH_EN enabled.

The safety timer is stopped in the following conditions:

•

Charging current below threshold (see Figure 7). The CHARGING/ATTACH output is

deasserted.

•

End of 3 hours (timer expires). The CHARGING/ATTACH output is deasserted.

•

ATTACH_EN transition to 0 (see Figure 8). The CHARGING/ATTACH output is intact

and the charging can continue without any time limit.

STCC5021 数据表(PDF) 17 Page - STMicroelectronics