TDA8358 View Datasheet(PDF) - Philips Electronics

Part Name

Description

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TDA8358

Full bridge vertical deflection output circuit in LVDMOS with east-west amplifier

Philips Electronics 

Philips Semiconductors

Full bridge vertical deflection output circuit

in LVDMOS with east-west amplifier

Product specification

TDA8358J

Guard circuit

A guard circuit with output pin GUARD is provided.

The guard circuit generates a HIGH-level during the

flyback period. The guard circuit is also activated for one

of the following conditions:

• During thermal protection (Tj ≈ 170 °C)

• During an open-loop condition.

The guard signal can be used for blanking the picture tube

and signalling fault conditions. The vertical

synchronization pulses of the guard signal can be used by

an On Screen Display (OSD) microcontroller.

Damping resistor compensation

HF loop stability is achieved by connecting a damping

resistor RD1 (see Fig.4) across the deflection coil.

The current values in RD1 during scan and flyback are

significantly different. Both the resistor current and the

deflection coil current flow into measuring resistor RM,

resulting in a too low deflection coil current at the start of

the scan.

The difference in the damping resistor current values

during scan and flyback have to be externally

compensated in order to achieve a short settling time.

For that purpose a compensation resistor RCMP is

connected between pins OUTA and COMP. The value of

RCMP is calculated by:

RCMP = -((--V-V---F-F--B-B----–-–---V-V----ll-o-o--s-s-s-s--(-(-F-F--B-B--)-)--–-–----V-I-c--P-o--)-i-l--(×-p---e-R--a--D-k---)1---×-×---R--(--R-c---o-S-i--l-)+----×-3----0R---0-M---)

where:

• Rcoil is the coil resistance

• Vloss(FB) is the voltage loss between pins VFB and OUTA

at flyback.

East-west amplifier

The east-west amplifier is a current driver sinking the

current of a diode modulator circuit. A feedback

resistor REWF (see Fig.4) has to be connected between

the input and output of the inverting east-west amplifier in

order to convert the east-west correction input current into

an output voltage. The output voltage of the east-west

circuit at pin OUTEW is given by:

Vo ≈ Ii × REWF + Vi

The maximum output voltage is Vo(max) = 68 V, while the

maximum output current of the circuit is Io(max) = 750 mA.

1999 Dec 22

5

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