L5963 datasheet(6/45 Pages) STMICROELECTRONICS

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Overview

L5963

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DocID028553 Rev 1

Overview

The L5963 integrates two switching mode synchronous step down converters, a linearly

regulated power supply, a protected high side driver and voltage detectors. To guarantee a

robust operation, all the outputs have independent thermal protection and current limitation.

The two switching mode synchronous step-down converters employ voltage mode control

and feed forward functions to provide good load regulation and line regulation. Each

converter has its own enable. The users can adjust the output voltage of the two converters

by an external resistor divider. If the converters need to work with a frequency different from

the free running frequency, in order to consider EMC performance in system level, they can

be synchronized to an external clock by applying it on the SYNCIN pin. The frequency

should be higher than half of the free running frequency. If there are more than one L5963 in

the system they can work in Master-Slave configuration, to make sure all the L5963 have

the same operating frequency of the Master device. This Master-Slave function is

implemented by a dedicated pin SYNCOUT which always gives the operating frequency of

DC/DC1 (for details, see the next chapter)

A dedicated voltage detector is integrated in the first switching converter to monitor DC/DC1

output. When the output voltage of DC/DC1 goes above the threshold, SW1OK is released

and goes back to high with configurable delay set by a capacitor on the SW1OKDLY pin.

The linear regulator can work as standby regulator with low Iq or as a non-standby regulator.

Connecting its enable ENLDO to its supply VINLDO the regulator works as a standby

regulator, while connecting ENLDO to signal lower than 5 V the regulator works as non-

standby regulator, with higher load capability but also higher quiescent current.

In standby state, i.e. only the linear regulator is powered and works as a standby regulator,

with a load below 100 μA the device has a quiescent current of just 25 μA.

The small drop-out voltage of the linear regulator allows its use with low operating supply

voltage.

In many cases, the linear regulator has to provide voltages to devices which need the reset

function, like a MCU: this is provided by the LDOOK output, that is pulled low when

VOUTLDO goes below a threshold. Once VOUTLDO returns above that threshold, with a

specified hysteresis, LDOOK goes back to high with a configurable delay set by a capacitor

on pin LDOOKDLY.

The high side driver is enabled by a dedicated pin and has a very low drop-out voltage.

Protection circuits, like independent thermal protection, OCP, OVP and some special

protections (loss of GND, SPU, short to supply and so on), are implemented to make it very

robust (see next chapter for details).

L5963 also embeds a voltage monitor (VDOUT), adjustable by means of an external resistor

divider, that can be used to sense the battery or other voltages in the system. Sensing

voltage is fed to pin VDIN. For instance, VDOUT might be used to monitor the output of

DC/DC2, realizing in this way the Power Good function for that block. VDOUT is pulled low

when voltage on VDIN goes below the specified threshold. Once VDIN returns above that

threshold, with a specified hysteresis, VDOUT goes back to high with a configurable delay

set by a capacitor on pin LDOOKDLY

Two different packages are available. The PowerSSO-36 slug-down allows to dissipate the

heat on the board and reduce the application size. The slug has to be connected to the

ground plane. This is the package suggested for standard applications. When this is not

enough, because the L5963 is used as pre-regulator for high consuming applications and

both the 2 DC-DC are working at high currents, the PSSO36 slug-up allows the use of a

heat-sink to make easier power dissipation.

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