TDA9109A datasheet(32/47 Pages) STMICROELECTRONICS

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TDA9109A

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2.4 Output Section

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

shaping stage which also controls the H-drive duty

cycle (I2C adjustable) (see Figure 11). In order to

secure the scanning power part operation, the out-

put is inhibited in the following cases:

• when V

CC or VDD are too low

• when the XRAY protection is activated

• during the Horizontal flyback

• when the HDrive I2C bit control is off

The output stage consists of a NPN bipolar tran-

sistor. Only the collector is accessible

(see Figure 13).

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.

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 inter-

face has to be added between the circuit and the

power transistor either of bipolar or MOS type.

2.5 X-RAY Protection

The X-Ray protection is activated by application of

a high level on the X-Ray input (8.2V on Pin 25). It

inhibits the H-Drive and B+ outputs.

This activation is internally delayed by 2 lines to

avoid erratic detection (short parasitics).

This protection is latched; it may be reset either by

VCC switch off or by I

2C (see Figure 14).

Figure 14. Safety Functions Block Diagram

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