TDA9109N datasheet(20/32 Pages) STMICROELECTRONICS

20 / 32 page

OPERATING DESCRIPTION (continued)

H-DRIVE

VCC

Figure 13

II.4 - Output Section

The H-drive signal is sent to the output through a

shaping stage which also controls the H-drive duty

cycle (I

2C adjustable) (see Figure 11). In order to

secure the scanning power part operation, the

output is inhibited in the following cases :

- when VCC or VDD are too low,

- when the XRAY protection is activated,

- during the Horizontal flyback,

- when the HDrive I

2C bit control is off.

The output stage consists of a NPN bipolar

transistor. Only the collector is accessible

(see Figure 13 ).

This output stage is intended for ”reverse” base

control, where setting the output NPN in off-state

will control the power scanning transistor in off-

state (see Application Diagram).

BOUT

HORIZONTAL

OUTPUT

INHIBITION

VERTICAL

OUTPUT

INHIBITION

Horizontal Flyback

0.7V

XRAY Protection

CC Checking

CC off or I

C Reset

XRAY

VSCinh

I2C Drive on/off

I2C Ramp on/off

Figure 14 : Safety Functions Block Diagram

The maximum output current is 30mA, and the

corresponding voltage drop of the output VCEsat is

0.4V Max.

Obviously the power scanning transistor cannot be

directly driven by the integrated circuit. An interface

has to be added between the circuit and the power

transistor either of bipolar or MOS type.

II.5 - X-RAY Protection

The X-Ray protection is activated by application of

a high level on the X-Ray input (8V on Pin 25).

It inhibits the H-Drive and B+ outputs.

This protection is latched ; it may be reset either by

VCC switch off or by I

2C (see Figure 14).

II.6 - Horizontal and Vertical Dynamic Focus

The TDA9109/N delivers a horizontal parabola

which is added on a vertical parabola waveform on

Pin 10. This horizontal parabola comes from a

sawtooth in phase with flyback pulse middle.This

sawtooth is present on Pin 9 where the horizontal

focus capacitor should be the same as C0 to obtain

the correct amplitude (from 2 to 4.7V typically).

Symmetry and amplitude are I

2C adjustable

(see Figure 15). The vertical dynamic focus is

tracked with VPOSand VAMP.Its amplitudecan be

adjusted. It is also affected by S and C corrections.

This positive signal once amplified is to be sent to

the CRT focusing grids.

TDA9109/N

20/32

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