THE L6569 AND ITS APPLICATIONS

The L6569

The L6569 is able to directly control a symmetric

half bridge inverter of a fluorescent lamp ballast,

or a low voltage halogen lamp transformer.Two

270mA buffers drive the inverter MOSFETs in

complementary fashion with a 1.25

µs built-in

dead time to prevent cross conduction. The buffer

for the upper Mosfet is driven through a 600V

level shifter realized in BCD off line technology.

The oscillator, similar to a CMOS 555 timer, oper-

ates from 25 to 150 kHz with a +/-5% maximum

tolerance. The internal 15V shunt regulator has a

9V Under Voltage Lock Out with an 1V hysteresis,

and the circuit requires only 150

µA at power up.

The L6569 integrates a high voltage Lateral

DMOS transistor in place of the usual external di-

ode [2] to charge the bootstrap capacitor for the

upper buffer. Figure 5 shows DMOS operating as

a synchronous rectifier.

The applications

The primary application for the L6569 is the Com-

pact Fluorescent Lamp. With the oscillator, the

supply and the Mosfet drivers it is the core of the

application, and designers can customize the cir-

cuit to their requirements.

RF

CF

HVG

OUT

LVG

BOOT

VS

GND

LEVEL

SHIFTER

LOGIC CONTROL

with DEAD TIME

LOW

SIDE

DRIVER

HIGH

SIDE

DRIVER

CHARGE

PUMP

UVLO

Figure 3: Block diagram of the L6569.

AC LINE

180K

Ω

L6569

10K

Ω

22

Ω

22

Ω

10

µF

10

µF

STD4NK50Z

LAMP

1nF

100nF

D02IN1385

Figure 4: Basic application diagram using the L6569 and two STD4NK50Z MOSFETs.

AN880 APPLICATION NOTE

2/14