L6928D View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

L6928D

High efficiency monolithic synchronous step-down regulator

STMicroelectronics 

L6928

6

Additional features and description

Additional features and description

6.1

Dropout operation

The Li-Ion battery voltage ranges from approximately 3 V and 4.1 V to 4.2 V (depending on

the anode material). If the regulated output voltage is from 2.5 V and 3.3 V, close to the

end of the battery life, the battery voltage goes down to the regulated one. In this case the

device stops switching, working at 100% of duty cycle, so minimizing the dropout voltage

and the device losses.

6.2

PGOOD

A Power Good output signal is available. The VFB pin is internally connected to a

comparator with a threshold set at 90% of the reference voltage (0.6 V). Since the output

voltage is connected to the VFB pin by a resistor divider, when the output voltage goes

lower than the regulated value, the VFB pin voltage goes lower than 90% of the internal

reference value. The internal comparator is triggered and the PGOOD pin is pulled down.

The pin is an open drain output and so, a pull-up resistor should be connected to him. If the

feature is not required, the pin can be left floating.

6.3

Adjustable output voltage

The output voltage can be adjusted by an external resistor divider from a minimum value of

0.6 V up to the input voltage. The output voltage value is given by the below equation:

Equation 4:

VOUT

=

0.6

.

(1 + R-----2-

R1

)

6.4

OVP (overvoltage protection)

The device has an internal overvoltage protection circuit to protect the load. If the voltage

on the feedback pin goes higher than an internal threshold set 10% (typ.) higher than the

reference voltage, the low-side power MOSFET turns on until the feedback voltage goes

lower than the reference one. During the overvoltage circuit intervention, the zero-crossing

comparator is disabled so that the device is also able to sink current.

6.5

Thermal shutdown

The device has also a thermal shutdown protection active when the junction temperature

reaches 150 °C. In this case both the high-side MOSFET and the low-side turn off. Once

the junction temperature goes back lower than 95 °C, the device restarts the normal

operation.

DocID11051 Rev 9

13/21

Share Link: