L6924U(2008) 查看數據表（PDF） - STMicroelectronics

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L6924U
(Rev.:2008)

USB compatible battery charger system with integrated power switch for Li-Ion/Li-Polymer

STMicroelectronics 

Operation description

L6924U

Neglecting the voltage drop across the charger (∆VMOS) when the device operates in this

condition, its input voltage is equal to the battery one, and so a very low operating input

voltage (down to 2.5 V) is required. The power dissipated by the device during this phase is:

Equation 4

PCH = RDS (on) × I LIM 2

When the battery voltage approaches the final value, the charger gets back the control of

the current, reducing it. Due to this, the upstream adapter exits the current limit condition

and its output goes up to the regulated voltage VADP. This is the worst case in power

dissipation:

Equation 5

PDIS = (VADP −VBAT ) × I LIM

In conclusion, the advantage of the linear charging approach is that the designer has the

direct control of the charge current, and consequently the application can be very simple.

The drawback is the high power dissipation.

The advantage of the quasi-pulse charging method is that the power dissipated is

dramatically reduced. The drawback is that a dedicated upstream adapter is required.

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