TDA9110 datasheet(19/29 Pages) STMICROELECTRONICS

19 / 29 page

H-DRIVE

VCC

Figure 15

II.4 - Output Section

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

shaping block ensuring Ts and H-drive duty cycle

(I2C adjustable) (see Figure 13). In order to secure

the scanning power part operation, the output is

inhibited in the following cases :

- when VCC is 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 transis-

tor. Only the collector is accessible(see Figure 15).

HORIZONTAL

OUTPUT

INHIBITION

VERTICAL

OUTPUT

INHIBITION

Horizontal Flyback

0.7V

XRAY Protection

CC Checking

CC off or I

C Reset

XRAY

Ref

I2C Drive on/off

I2C Ramp on/off

Figure 16 : Safety Functions Block Diagram

OPERATING DESCRIPTION (continued)

The output NPN is in off-state when the power

scanning transistor is also in off-state.

The maximum output current is 30mA, and the

corresponding voltage drop of the output VCEsat is

0.4V typically.

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 of 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). The

consequencies of X-Ray protection are :

- inhibition of H-Drive output

- activation of vertical blanking output.

This protection is reset either by VCC switch off or

by I

2C (see Figure 16).

II.6 - Horizontal and Vertical Dynamic Focus

The TDA9110 delivers a horizontal parabola which

is added on a vertical parabola waveform on Pin

15. This horizontal parabola comes from a saw-

tooth. The phase advance versus Horizontal fly-

back middle is kept constant for each frequency

(about 860ns). This sawtooth is present on Pin 16

where the horizontal focus capacitor is the same

as C0 to obtain a controlled amplitude (from 2 to

4.7V typically).

Symmetry (keystone) and amplitude areI

2C adjust-

able (see Figure 17). 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 has to be connectedto the CRT

focusing grids.

TDA9110

19/29

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