34675 datasheet(13/24 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34675

FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

Figure 26. 34675 Functional Internal Block Diagram

INTEGRATED SUPPLY

Internal Supply and Reference

This block steps down the high input voltage to a lower

voltage which powers all the internal blocks. In addition, this

block generates the reference voltage for the charge-control

block.

SENSING & CONTROL

VIN (Input Voltage) Monitor

The input voltage monitor block monitors the input voltage

for two thresholds, power-on-reset (POR) and over-voltage

protection (OVP). If the input is lower than the POR or higher

than the OVP threshold, this block outputs a logic signal to

disable the charger and the linear regulator.

Current Setting & Monitor

This block sets the charge current in the constant-current

mode, and monitors the actual charge current during the

whole charge cycle.

Charge Control

The charge control block controls the gate voltage of the

power MOSFET to regulate the charge current, the battery

voltage, or the die temperature. It can also completely turn off

the power MOSFET, to stop the current flow between the

input and the battery. Additionally, monitoring of the charge

current and the charger output voltage determines the trickle-

charge mode and the recharge cycle.

EOC (End of Charge)

The EOC block monitors the charge current and the

battery voltage for the EOC conditions. Once the EOC

conditions are reached, this block outputs a logic signal to

indicate the end of the charge.

VIN-BAT Comparator

The VIN-BAT comparator monitors the voltage difference

between the input voltage and the battery voltage. The input

voltage has to be higher than the battery voltage for the

charger to be enabled. If the input voltage falls below the

battery voltage, this block outputs a signal to disable the

charger to prevent the leakage current from the battery to the

input.

MC34675 - Functional Block Diagram

Integrated Supply

Sensing & Control

Outputs

Logic

Integrated Supply

Internal Supply & Reference

Sensing & Control

Logic

Die Temperature Feedback

Current Setting

Current Monitor

Status Indication

VIN - BAT Comparator

VIN Monitor

Charge Control

Logic Control

End of Charge

Outputs

Power MOSFET

Linear Regulator

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