L6590A datasheet(2/19 Pages) STMICROELECTRONICS

2 / 19 page

L6590A

2/19

DESCRIPTION (continued)

The MOSFET is source-grounded, thus it is possible

to build flyback, boost and forward converters.

The device is meant to work with secondary feed-

back for tight tolerance of the regulated output volt-

age.

The internal fixed oscillator frequency and the inte-

grated non dissipative start-up generator minimize

the external component count and power consump-

tion.

The device is equipped with a standby function that

automatically reduces the oscillator frequency from

65 to 22 kHz under light load conditions to enhance

efficiency (Pin <1W @ Pout = 0.5W with wide range

mains).

Internal protections like cycle-by-cycle current limit-

ing, latched output overvoltage protection, mains un-

dervoltage

protection

and

thermal

shutdown

generate a 'robust' design solution.

The IC uses a special leadframe with the ground pins

(6, 7 and 8) internally connected in order for heat to

be easily removed from the silicon die. An heatsink

can then be realized by simply making provision of

few cm2 of copper on the PCB. Furthermore, the pin

close to the high-voltage one is not connected to

ease compliance with safety distances on the PCB.

BLOCK DIAGRAM

PIN CONNECTIONS (Top view)

SUPPLY

&UVLO

OVER

VOLTAGE

OVER

CURRENT

2.5V

DRAIN

(1)

VCC

(3)

BOK

(5)

COMP

(4)

GND

(6,7,8)

VREF

1mA

BROWNOUT

PWM

STANDBY

START-UP

OSC

65/22 kHz

THERMAL

S.DOWN

BOK

DRAIN

N.C.

Vcc

COMP

GND

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