L6668

2/23

2

Description

L6668 is a current-mode primary controller IC, designed to build single-ended converters.

The IC drives the system at fixed frequency at heavy load and an improved Standby function causes a

smooth frequency reduction as the load is progressively reduced. At very light load the device enters a

special operating mode (burst-mode with fixed, externally programmed peak current) that, in addition to

the on-board high-voltage start-up and the very low quiescent current, helps keep low the consumption

from the mains and be compliant with energy saving regulations. To allow meeting compliance with these

standards in power-factor-corrected systems too, an interface with the PFC controller is provided that en-

ables to turn off the pre-regulator when the load level falls below a threshold.

The IC includes also a programmable soft-start, slope compensation for stable operation at duty cycles

greater then 50%, a disable function, a leading edge blanking on current sense to improve noise immunity,

latched disable for OVP or OTP shutdown and an effective two-level OCP able to protect the system even

in case the secondary diode fails short.

Table 2. Absolute Maximum Ratings

Table 3. Thermal Data

Figure 3. Pin Connection (Top view)

Symbol

Pin

Parameter

Value

Unit

5

IC Supply voltage (Icc = 20 mA)

Self-limited

V

1

High-voltage start-up generator voltage range

-0.3 to 700

V

1

High-voltage start-up generator current

Self-limited

A

---

Analog Inputs & Outputs, except pin 14

-0.3 to 8

V

14

Max. sink current (low state)

2

mA

14

Max. voltage (open state)

16

V

Power Dissipation @Tamb = 50°C

0.75

W

Junction Temperature Operating range

-25 to 150

°C

Storage Temperature

-55 to 150

°C

Symbol

Parameter

Value

Unit

Thermal Resistance Junction to AmbientMax

120

°C/W

VREF

SKIPADJ

HV

HVS

GND

OUT

Vcc

N.C.

DIS

RCT

S-COMP

PFC_STOP

STBY

ISEN

SS

COMP

VREF

SKIPADJ

HV

HVS

GND

OUT

Vcc

N.C.

DIS

RCT

S-COMP

PFC_STOP

STBY

ISEN

SS

COMP