SABRE-LL-I datasheet(69/141 Pages) STMICROELECTRONICS

69 / 141 page

SABRE-LL-I

Power bridges

69/141

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 S.A.B.Re will enter in reset state

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

of its internal blocks.

Battery charger regulator application (CC-CV).

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 next battery

charger profile) will not be considered during start up sequence.

Voltage regulation

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

VREF_FB pin. S.A.B.Re 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

Reference voltages values can be changed using a metal layer change in order to adapt

them to customer system.

The first, second and third reference voltage has been chosen to regulate 3.3V, 4.2V and

5V with the same resistor divider network, such that the commutation between different

regulated voltages can be done on the fly in the application.

Current regulation

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 the

regulated current: the voltage provided at the IREF_FB pin will be compared to the internal

reference. S.A.B.Re has the possibility to choose between four voltage references using the

serial interface, writing the SelCurrRef[1:0] bits in the Aux3SwCfg1 register according to the

following the table:

Table 47.

Battery charger control loop FBRef specification

Aux3SwCfg1

Reference voltage (FBRef)

Comments

SelFBref[1]

SelFBref[0]

Min

Typ

Max

Unit

1.370

1.412

1.455

1.746

1.8

1.854

Default state

2.079

2.143

2.207

2.425

2.5

2.575

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