TDA8354Q View Datasheet(PDF) - Philips Electronics

Part Name

Description

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TDA8354Q

Full bridge current driven vertical deflection output circuit in LVDMOS

Philips Electronics 

Philips Semiconductors

Full bridge current driven vertical

deflection output circuit in LVDMOS

Product specification

TDA8354Q

Guard circuit

A guard circuit with output signal Vo(guard) is provided.

The guard circuit generates an active HIGH level during

the flyback period. The guard circuit is also activated for

one or more of the following conditions:

• When the thermal protection is activated (Tj ≈ 170 °C)

• During short circuit of the output pins (pins 5 and 9)

to VP or ground

• During open coil

• During open loop

• During short circuit of the input pins to VP or ground.

An active HIGH level of the guard signal is also generated

for the following conditions:

• No drive signal

• Short circuit of the coil.

However, for these events, the signal is generated via an

internal timer circuit. The guard signal set via this timer has

a delay of ≈120 ms. The delay time is given by the lowest

applicable field frequency.

The guard signal can be used to blank the picture tube

screen and signal a fault condition. The guard signal can

also be used as a vertical synchronisation input pulse for

an On Screen Display (OSD) microcontroller.

Damping resistor compensation

For HF loop stability, a damping resistor is connected

across the deflection coil. There is a large difference in

current in the damping resistor Rp during scan and flyback.

The resistor current is summed to the current in the

deflection coil via the measuring resistor RM, which results

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

scan.

To reach a short settling time, the difference in the current

during scan and flyback in the damping resistor can be

compensated by external means. For this purpose, a

resistor (Rcomp) of about 1 MΩ can be connected between

the output of output stage A (pin 9) and pin 13 (Icomp).

For a more accurate calculation of Rcomp, we have:

Rcomp = -(--V-(--V-f--l-b-f-l--b–----–-V---V-l-o--l-s-o--s-s--s–----–-V----IP-L---)-×--×---R--R---L--p-)---××----R-R----c-M--o--n-

2001 Jul 11

5

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