L6460 datasheet(76/139 Pages) STMICROELECTRONICS

76 / 139 page

Power bridges

L6460

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Doc ID 17713 Rev 1

14.1.8

Battery charger or switching regulator (Bridge 4)

The functionality of this circuit is obtained by using the bridge 4 output stage. This circuit is

powered directly from VSupply and it is intended to be used as a battery charger or a

switching regulator.

The control loop block diagram is shown in the Figure 21.

Figure 21.

Battery charger control loop block diagram

The battery charger control loop implements an asynchronous switching regulator intended

to be used as a constant voltage/constant current programmable source.

When used as a simple switching regulator, it could be a system regulator depending on

startup configurations

When a system regulator under-voltage event is detected L6460 will enter in reset state

signaling this event to the microcontroller by pulling low the nRESET pin and disabling most

of its internal blocks.

When the control loop is intended to be used as a battery charger, the Aux3BatteryCharge

bit must be written in the Aux3SwCfg1 register. This is because in this case the

undervoltage event that will be sure present when charging a battery (see battery charger

profile in Figure 22) will not be considered during start up sequence.

The regulated output voltage will be externally set by a resistor divider network connected to

VREF_FB pin. L6460 has the possibility to choose between four voltage references (and, as a

consequence, four under-voltage thresholds) using the serial interface. The feedback

reference voltage selection is made by writing the SelFBRef[1:0] bits in the Aux3SwCfg1

The regulation of the output current can be done externally, by using a sense resistor

connected in series on the path that provides current to the load. By using an external

differential amplifier the customer can set the desired V = f(I) characteristic, and therefore

IREF_FB

VREF_FB

COMP_I

COMP_V

PULSE SKIPPING

BURST

CONTROL LOGIC

PEAK CURRENT

MODE CONTROL

LOGIC

BRIDGE 4

PARALLELED

POWER

STAGE

SelFBRef<1:0>

DC4_plus

DC4_minus

SelCurrRef<1:0>

DIFF

AMPLI

LOAD

FBRef

CurrRef

Ilimit

PWM

L6460

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