HA16114P 参数 Datasheet PDF下载

HA16114P/PJ/FP/FPJ, HA16120FP/FPJ

1.2 External Synchronization

These ICs have a sync input pin so that they can be synchronized to a primary-control AC/DC converter.

Pulses from the secondary winding of the switching transformer should be dropped through a resistor

voltage divider to the sync input pin. Synchronization takes place at the falling edge, which is optimal for

multiple-output power supplies that synchronize with a flyback AC/DC converter.

The sync input pin (SYNC) is connected internally through a synchronizing circuit to the sawtooth

oscillator to synchronize the sawtooth waveform (see figure 1.2).

•

Synchronization is with the falling edge of the external sync signal.

•

The frequency of the external sync signal must be in the range f

OSC

< f

SYNC

< f

OSC

×

2.

•

The duty cycle of the external sync signal must be in the range 5% < t

1

/t

2

< 50% (t

1

= 300 ns Min).

•

With external synchronization, V

TH

'

can be calculated as follows.

V

TH

' = (V

TH

−

V

TL

)

×

f

OSC

+ V

TL

f

SYNC

Note: When not using external synchronization, connect the

SYNC

pin to the Vref pin.

V

TH

(1.6 V typ)

Sawtooth wave

(f

OSC

)

V

TL

(1.0 V typ)

V

TH

'

SYNC

pin

(f

SYNC

)

Synchronized

at falling edge

t

1

t

2

1V

Vref

Figure 1.2 External Synchronization

Rev.2.0, Sep.18.2003, page 8 of 37