HA16114FP View Datasheet(PDF) - Hitachi -> Renesas Electronics

Part Name

Description

Manufacturer

HA16114FP

Switching Regulator for Chopper Type DC/DC Converter

Hitachi -> Renesas Electronics 

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 fOSC < fSYNC < fOSC × 2.

• The duty cycle of the external sync signal must be in the range 5% < t1/t2 < 50% (t1 = 300 ns Min).

• With external synchronization, VTH' can be calculated as follows.

VTH’ = (VTH − VTL) ×

fOSC

fSYNC

+ VTL

Note: When not using external synchronization, connect the SYNC pin to the Vref pin.

VTH (1.6 V typ)

Sawtooth wave

(fOSC)

VTL

(1.0 V typ)

SYNC pin

(f SYNC )

Synchronized

t1

at falling edge

t2

Figure 1.2 External Synchronization

VTH

Vref

1V

8

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