L6668

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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.

Note:

1. ESD immunity for pin 1 is guaranteed up to 900V (Human Body Model).

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