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TDA4866

Full bridge current driven vertical deflection booster

Philips Electronics 

Philips Semiconductors

Full bridge current driven vertical deflection

booster

Product specification

TDA4866

handbook, halfpage

INA 1

INB 2

VP 3

OUTB 4

GND 5 TDA4866

OUTA 6

VFB 7

GUARD 8

FEEDB 9

MHB936

Fig.2 Pin configuration (SIL version).

INA 1

INB 2

VP 3

OUTB 4

GND 5

OUTA 6

VFB 7

GUARD 8

FEEDB 9

TDA4866J

MHB937

Fig.3 Pin configuration (DBS version).

FUNCTIONAL DESCRIPTION

The TDA4866 consists of a differential input stage, two

output stages, a flyback generator, a protection circuit for

the output stages and a guard circuit.

Differential input stage

The differential input stage has a high CMRR differential

current mode input (pins 1 and 2) that results in a high

electro-magnetic immunity and is especially suitable for

driver units with differential (e.g. TDA485x, TDA4841PS)

and single ended current signals. Driver units with voltage

outputs are simply applicable as well (e.g. two additional

resistors are required).

The differential input stage delivers the driver signals for

the output stages.

Output stages

The two output stages are current driven in opposite phase

and operate in combination with the deflection coil in a full

bridge configuration. Therefore the TDA4866 requires no

external coupling capacitor (e.g. 2200 µF) and operates

with one supply voltage VP and a separate adjustable

flyback supply voltage VFB only. The deflection current

through the coil (Idefl) is measured with the resistor Rm

which produces a voltage drop (Urm) of: Urm ≈ Rm × Idefl.

At the feedback input (pin 9) a part of Idefl is fed back to the

input stage. The feedback input has a current input

characteristic which holds the differential voltage between

pin 9 and the output pin 4 on zero.

Therefore the feedback current (I9) through Rref is:

I9 ≈ R--R---r-m-e--f × Idefl

The input stage directly compares the driver currents into

pins 1 and 2 with the feedback current I9. Any difference of

this comparison leads to a more or less driver current for

the output stages. The relation between the deflection

current and the differential input current (Iid) is:

Iid = I9 ≈ R--R---r-m-e--f × Idefl

Due to the feedback loop gain (VU loop) and internal

bondwire resistance (Rbo) correction factors are required

to determine the accurate value of Idefl:

Idefl = Iid × -R----m---R--+--r--e-R--f---b---o- × 1 – V-----U--1--l-o---o--p-

with Rbo ≈ 70 mΩ and





1

–

V-----U--1--l-o---o--p-

≈ 0.98

for Idefl = 0.7 A.

The deflection current can be adjusted up to ±1 A by

varying Rref when Rm is fixed to 1 Ω.

High bandwidth and excellent transition behaviour is

achieved due to the transimpedance principle this circuit

works with.

2001 Aug 07

4

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