STCC5011 Datasheet, PDF (16/37 Pages) STMicroelectronics – Constant current mode overcurrent protection

Application information
STCC5011, STCC5021
5.5
Attach detection
The STCC5011-STCC5021 can detect peripheral device attachments when the host system
is in S4/S5 deep sleep states or in G3 shutdown state.
In these states, when no peripheral device is attached, the host system can save power by
switching off the high-power DC-DC converter and switching on a low-power LDO on the IN pin of
the device. When an attach event is detected, the device asserts the CHARGING/ATTACH
output allowing the host system to turn off the low power LDO and turn on the high power DC-
DC converter and start charging.
The attach detection feature is enabled with the combination of logic low level on EN and
logic high on ATTACH_EN (see Table 6). The devices already attached when activating the
attach detection circuit (EN = 0, ATTACH_EN = 1) are ignored and their current consumption is
limited to 500 μA. Only devices attached after activation of the attach detection circuit are
detected.
ATTACH_EN
0
1
1
Table 6. Attach detector truth table
EN
x
1
0
Attach detector
OFF
OFF
ON
The attach detection block is supplied by the V_DD power supply pin. It has a very low
consumption (12 µA typ.) and accepts a wide supply voltage range (1.7 V up to 5.5 V). The
V_DD power supply must be provided by a dedicated low power LDO.
The attach detector monitors voltage drop across a bypass switch between V_DD and the
OUT pin. The bypass switch is enabled only when the attach detector is turned on. This
voltage drop is caused either by the supply current of the attached device or by inrush
current for charging device internal capacitors.
The open drain active low output CHARGING/ATTACH is asserted upon device detection,
alerting the host system of device attachment. It stays asserted for the t_ATTACH delay
(25 s typically). During this time, the host system may switch the IN pin from low power LDO
to 5 V high-power supply and set proper CTLx configuration (see Figure 6).
The attached device can start charging keeping CHARGING/ATTACH asserted. If charging
does not occur, the flag is deasserted after the t_ATTACH (the attached device removed or
charging current drops below threshold or safety timer expires - see Section 5.6).
The supply voltage of the low-power LDO connected to the IN pin, when the system is in
power saving mode, must not be lower than the V_DD power supply voltage level and must
not be greater than 5.5 V.
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