LCS705LG datasheet(3/30 Pages) POWERINT

3 / 30 page

Rev. G 05/15

LCS700-708

www.power.com

Pin Functional Description

VCC Pin

IC power pin. In a typical application, VCC is connected to the 12 V

system standby supply via a 5 W resistor. This resistor helps provide

filtering and improves noise immunity.

Note: The system standby supply return should be connected to the

B- bus and not to the GROUND pin.

VREF Pin

3.4 VREF pin. An internal voltage reference network used as a

voltage source for FEEDBACK pin and DT/BF pin pull-up resistor.

GROUND (G) Pin

G is the return node for all analog small signals. All small signal pin

bypass capacitors must be returned to this pin through short traces,

with the exception of the D-S high-voltage bypass capacitor, and the

VCCH bypass capacitor. It is internally connected to the SOURCE pins

to provide a star connection. Do not connect the GROUND pin to

the SOURCE pins, nor to the B- bus, in the PCB layout.

OV/UV Pin

Overvoltage/Undervoltage pin. B+ is sensed by this pin through a

resistor divider. The OV/UV pin implements brown-in, brown-out, and

overvoltage lockout with hysteresis. Pulling this pin down to ground

will implement a remote-off function.

FEEDBACK (FB) Pin

Current fed into this pin determines LLC switching frequency; higher

current programs higher switching frequency. The pin V-I character-

istic resembles a diode to ground during normal switching. An RC

network between the VREF pin and FEEDBACK pin determines the

minimum operating frequency, start-up frequency, soft-start time, and

delay before start-up.

DEAD-TIME/BURST FREQUENCY (DT/BF) Pin

A resistor divider from VREF to ground programs dead-time,

maximum switching frequency at start-up, and burst-mode threshold

frequencies.

CURRENT-SENSE (IS) Pin

The CURRENT-SENSE pin is used for sensing transformer primary

current, to detect overload and fault conditions, through a current

sense resistor or a capacitive divider plus sense resistor circuit. It

resembles a reverse diode to ground, and does not require a rectifier

circuit for preventing negative pulses from reaching the pin, provided

the reverse current is limited to <5 mA.

SOURCE (S1), (S2) Pins

SOURCE pins of internal low-side MOSFET. These should be

connected together on the PCB, and connected to the B- from the

PFC bulk capacitor or input high-voltage DC return.

HB Pin

This is the output of the half-bridge connected MOSFETs (Source of

high-side MOSFET, Drain of low-side MOSFET), to be connected to

the LLC power train (transformer primary and series resonant

capacitor).

VCCH Pin

Floating bootstrap supply pin for the LLC high-side driver. This pin is

referenced to the HB pin, which in turn is internally connected to the

SOURCE pin of the high-side MOSFET. A bypass/storage capacitor

between VCCH and HB pins, and a boot strap diode with a series

resistor from the standby supply, are required. The storage capacitor

is refreshed every time the lower MOSFET turns on or its body diode

conducts.

DRAIN (D) Pin

DRAIN pin of the internal high-side MOSFET. This connects to the B+

from the PFC bulk capacitor or input high-voltage DC bus.

Figure 3. Pin Numbering and Designation.

PI-6757-120214

H Package (eSIP-16J)

(Front View)

L Package (eSIP-16K)

(Front View)

1314

9 10

3 4 5 6 7

Exposed Metal (Both H and L

Packages) (On Package Edge)

Internally Connected

Pin 1 I.D.

LCS705LG Datasheet(PDF) 3 Page - Power Integrations, Inc.

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