TEA1504 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TEA1504

GreenChip™ SMPS control IC

Philips Electronics 

Philips Semiconductors

GreenChip™ SMPS control IC

Preliminary specification

TEA1504

(2)

11 V

VVaux

(4)

8.05 V

(3)

(1)

t

Vo

VG

(power

MOSFET)

off

switching

t

t

MGS572

(1) Start-up current source charges Caux.

(2) Start-up voltage.

(3) UVLO level.

(4) Auxiliary winding charges Caux.

Fig.4 Normal start-up waveforms.

Reference

All reference voltages are derived from a temperature

compensated, on-chip, band-gap. The band-gap

reference voltage is also used with an external

resistor (RREF) connected to REF (pin 8), to generate

accurate, temperature independent, IC internal

bias currents. IREF = R-V----RR----EE---FF- [A] .

RREF also affects the frequency of the oscillator (see

Section “Oscillator”).

Sample-and-hold

The TEA1504 uses voltage feedback with an innovative

sample-and-hold circuit to regulate the output voltage.

In a primary feedback configuration, the sample-and-hold

circuit samples the current into DEM (pin 13), fed by RDEM,

which relates to the output voltage (Vo) during the period

that current flows in the secondary winding.

aVo = IREF × RDEM + Vclamp(DEM)(pos).

Vclamp(DEM)(pos) is specified in Chapter “Characteristics”;

‘a’ = a constant determined by the turns ratio of the

transformer.

The sampled current is held in the external capacitor

(CCTRL). The PWM uses the voltage on CCTRL to set the

operating duty cycle of the power MOSFET. When the

TEA1504 is used in a secondary feedback configuration,

the feedback voltage is provided by an opto-coupler.

handbook, full pagewidth

VVaux

normal operation

fault condition

(1)

VG

(power

MOSFET)

(1) Start-up current source charges Caux.

switching off

Fig.5 Safe-restart mode waveforms.

1999 Dec 07

6

MGS647

t

t

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