L6571AD datasheet(4/8 Pages) STMICROELECTRONICS

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OSCILLATOR FREQUENCY

The frequency of the internal oscillator can be programmed using external resistor and capacitor.

The nominal oscillator frequency can be calculated using the following equation:

Where RF and CF are the external resistor and capacitor.

The device can be driven in "shut down" condition keeping the CF pin close to GND, but some cares have to be

taken:

1. When CF is to GND the high side driver is off and the low side is on

2. The forced discharge of the oscillator capacitor CF must not be shorter than 1us: a simple way to do this is to

limit the current discharge with a resistive path imposing R · CF >1µs(see fig.1)

Figure 1.

Figure 2. Waveforms

Duty Cycle, Ratio Between Dead

Time + Conduction Time of High

Side and Low Side Drivers

0.45

0.5

0.55

IAVE

Average Current from Vs

No Load, fs = 60KHz

1.2

1.5

fout

Oscillation Frequency

RT = 12K; CT = 1nF

kHz

Symbol

Parameter

Test Condition

Min.

Typ.

Max.

Unit

OSC

In2

⋅⋅

⋅

-----------------------------------------

1.3863 R

⋅⋅

------------------------------------------

GNDM

fault signal

VCF

LVG

D96IN434

VSUVP

ELECTRICAL CHARACTERISTCS (continued)

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