TDA9103 datasheet(15/27 Pages) STMICROELECTRONICS

15 / 27 page

H-DRIVE

VCC

H-DRIVE

VCC

Figure 17 : Output stage simplified diagram,

showing the two possibilities of

connection

The output Darlington is in off-state when the power

scanning transistor is also in off-state.

The maximum output current is 20mA, and the

correspondingvoltage drop of the output darlington

is 1.1V typically.

It is evident that the power scanning transistor

cannot be directly driven by the integrated circuit.

An interface has to be designed between the circuit

and the power transistor which can be of bipolar or

MOS type.

Outputs inhibition : the application of a voltage

lower than 1V (typ.) on Pin 2 (duty cycle adjust)

inhibits the horizontal, vertical and SMPS outputs.

This is not memorised.

X-ray protection : the activation of the X-ray protec-

tion is obtained by application of a high level on the

X-ray input (>1.6V). Consequences of X-ray pro-

tection are :

- Inhibition of H drive output.

- Inhibition of SPMS output.

- Activation of safety blanking output.

The reset of this protection is obtained by VCC

switch off.

S Correction. S Outputs

In the case where the ”S correction” of the horizon-

tal scanning is performed using capacitors, it is

necessary to switch capacitors when the frequency

changes.

For this the outputs S1, 2, 3 and 4 (Pins 9, 8, 7 and

16) give an indication about the horizontal frequency

by monitoring thecontrol voltage of the VCO (Pin 12).

The switching of the S outputs occurs for the fol-

lowing value of the control voltage.

S 2

2.4V

S 4

3.7V

The use of comparators with hysteresis avoids

erratic switching of the Sout outputs if the control

voltage of the VCO remains very close to a switch-

ing reference level.

SMPS

This unit generates the supply voltage for the hori-

zontal scanning system. This supply voltage is

approximately proportional to the H frequency in

order to keep the scanning amplitude constant

when the frequency changes. More precisely the

amplitude regulation is obtained by detecting and

regulating the ”flyback” amplitude or EHT value.

The power supply is a step-up converter and it uses

the ”current-mode” regulation principle.

The power supply works in synchronism with the

horizontal scanning. The switching power transis-

tor (external to the TDA9103) is switched on at the

beginning of the positive slope of the horizontal

sawtooth. It is switched off as required by the

integrated regulator. The current in the switching

power transistor is monitored and limited, and the

ratio Ton/Ton+Toff of the power transistor is limited

to 75% typically providing a very good reliability to

the power supply.

TDA9103

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