LM3655 datasheet(7/21 Pages) NSC

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11.0 Charge Control Functions (Continued)

The Shunt Regulator (Z1) on the V

DETECT pin is designed to sink a limited amount of current while maintaining certain levels of

regulation. These are specified below. When there is excessive current flowing into the V

DETECT pin above which Z1 can regulate,

then current can flow through D1 into the cell pin. When the cell pin voltage exceeds V

SHUNT,ICELL_SHUNT turns on. The

CELL_SHUNT circuit is implemented redundantly. ICELL_SHUNT shunts current to ground through effectively 100

Ω when both

redundant circuits are operating.

DETECT circuit parametric specs are summarized below. These specs apply to the entire Normal Temperature Range.

Parameter

Description

Min

Typ

Max

Units

DETECTMIN1

Min V

DETECT pin current to allow detection of a charger

100

µA

UNDETECTMAX

Maximum current into the V

DETECT pin for the charger to be not

detected.

3µA

DETECTMIN2

Once a charger is detected, it will remain detected unless the

current into the V

DETECT pin goes below this threshold

µA

CELL_SHUNT

CELL current.

With V

CELL = 4.5V (> VSHUNT)

DETECTMAX

Max V

DETECT pin current that can maintain VDETECTMAX1

DETECTMAX1

Normal V

DETECT regulation voltage, IDETECTMIN < IDETECT <

DETECTMAX

CELL

–5 mV

CELL

± 50 mV

DETECTMAX2

Secondary V

DETECT voltage limit, IDETECTMAX < IDETECT

< 30 mA

CELL 1V

11.2.2 Debounce Function

The charger debounce detects a temporary disconnect/connect of the charging power supply. This can occur when the end-user

inserts the power supply to the phone and the connection is not made cleanly, or if the connection is disturbed (such as dropping

the phone).

When the IC first senses the power supply input voltage it will delay

DEBOUNCE_ON before the charger detect signal is confirmed.

If there is disconnect of the charge power supply, the IC will delay

DEBOUNCE_OFF before the disconnection is confirmed. The IC

will ignore the interruptions of duration shorter than specified. These specs apply to the entire Normal Temperature Range.

20111505

FIGURE 2. V

DETECT Circuit

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