NTE7134 데이터 시트보기 (PDF) - NTE Electronics
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NTE7134 Datasheet PDF : 17 Pages
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Functional Description (Cont’d):
Supply Voltage Stabilizer, Reference and Protection (Cont’d)
When protection mode is active, several pins of the ASDC are forced into a defined state:
HDRV (Horizontal Driver Output) is floating
BDRV (B+ Control Driver Output) is floating
VOUT1 and VOUT2 (Vertical Outputs) are floating
CLBL provides a continuous blanking signal
The capacitor at HPLL2 is discharged
If the protection mode is activated via the supply voltage at Pin9, all thesae actions will be performed
in a well defined sequence. For activation via X–ray protection or HPLL2 all actions will occur simulta-
neously.
The return to normal operation is performed in accordance with the start–up sequence, if the reset
was caused by the supply voltage at Pin9. The first action with increasing supply voltage is the activa-
tion of continuous blanking at CLBL. When the threshold for activation of HDRV is passed, an internal
current begins to sharge the external capacitor at HPLL2 and PLL2 soft start sequence is performed.
In the beginning of this phase the horizontal driver stage generates very small output pulses. The
width of these pulses increases with the voltage at HPLL2 until the final duty cycle is reached. Then
the PLL2 voltage passes the threshold for activation of BDRV, VOUT1 and VOUT2.
For activation of these pins not only the PLL2 voltage, but also the supply voltage, must have passed
the appropriate threshold. A last pair of thresholds has to be passed by PLL2 voltage and supply volt-
age before the continuous blanking is finally removed, and the operation of PLL2 and frequency–
locked loop is enabled.
A return to the normal operation by releasing the voltage at HPLL2 will lead to a slightly different se-
quence. Here the activation of all functions is influenced only by the voltage at HPPL2.
Application hint: Internal discharge of the capacitor at HPLL2 will only be performed, if the protec-
tion mode was activated via the supply voltage or X–ray protection.
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