L6574 datasheet(2/10 Pages) STMICROELECTRONICS

2 / 10 page

L6574

2/10

PIN CONNECTION (top view)

THERMAL DATA

Symbol

Parameter

DIP16

SO16N

Unit

Rth j-amb

Thermal Resistance Junction to ambient

Max.

120

°C/W

PIN DESCRIPTION

N°

Function

CPRE

Preheat Timing Capacitor. The capacitor CPRE sets the preheating and the frequency shift time,

according to the relations: tPRE = KPRE · CPRE and tSH = KFS · CPRE (typ. KPRE = 1.5s/µF, KFS =

0.15s/

µF). This feature is obtained by charging CPRE with two different currents. During tPRE

this current is independent of the external components, so CPRE is charged up to 3.5V (preheat

timing comparator threshold). During tSH the current depends on RPRE value (i.e. on the differ-

ence between fPRE and fIGN). In this way tSH is always set at 0.1tPRE. In steady state the voltage

at pin 1 is 5V.

RPRE

Maximum Oscillation Frequency Setting. The resistance connected between this pin and ground

sets the fPRE value, fixing the difference between fPRE and fIGN (fPRE > fIGN). At the end of the

Start-up procedure, the effect current drown from RPRE is over. The voltage at this pin is fixed at

VREF =2V.

Oscillator Frequency Setting. The capacitor CF, along with to RPRE and RIGN, sets fPRE and fING.

In normal operation this pin shows a triangular wave.

RIGN

Minimum Oscillation Frequency Setting. The resistance connected between this pin and ground

sets the fIGN value. The voltage at this pin is fixed at VREF =2V.

OPout

Out of the operational amplifier. To implement a feedback control loop this pin can be connected

to the RIGN pin by means an appropriate circuitry.

OPin-

Inverting Input of the operational amplifier.

OPin+

Non Inverting Input of the operational amplifier.

EN1

Enable 1. This pin (active high), forces the device in a latched shutdown state (like in the under

voltage conditions). There are two ways to resume normal operation:

– the first is to reduce the supply voltage below the undervoltage threshold and then

increase it again until the valid supply is recognised.

– the second is activating EN2 input.

The enable 1 is especially designed for strong fault (e.g. in case of lamp disconnection).

CPRE

RPRE

RING

OPOUT

OPIN+

OPIN-

GND

LVG

N.C.

OUT

HVG

VBOOT

D97IN492

EN1

EN2

L6574 数据表(PDF) 2 Page - STMicroelectronics

L6574 数据表(HTML) 2 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10

数据表下载