BQ24100 Datasheet, PDF (21/26 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

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PCB LAYOUT CONSIDERATION (continued)
bq24100, bq24103
bq24105, bq24108
bq24113, bq24115
SLUS606C – JUNE 2004 – REVISED SEPTEMBER 2005
Fast Charge: This is captured during the constant-current phase. The two negative spikes are the result of the
short delay when switching between the top and bottom FETs. The break-before-make action prevents current
shoot-through and results in a body diode drop below ground potential during the break time.
Charge during Voltage Regulation and Approaching Termination: Note that this waveform is similar to the
precharge waveform. The difference is that the battery voltage is higher so the duty cycle is slightly higher. The
bottom FET stays on longer because there is more of a current load than during precharge; it takes longer for the
inducator current to ramp down to the current threshold where the synchronous FET is disabled.
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