ViewSonic E70FSB-2 Service Manual - Page 14

Confidential - Do Not Copy

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4-2 DEFLECTION CIRCUIT The deflection circuit is achieved by a high performance and efficient solution IC 401 (TDA4841) for this monitor. The concept is fully DC controllable and can be used in applications with a micro-controller solutions. The TDA4841 provides sync. Processing with full auto sync. Capability, a flexible SMPS block and an extensive set of geometry control facilities. Further the IC generates the drive waveforms for DC coupled vertical boosters to the TDA4863. Horizontal Oscillator The oscillator is of the relaxation type and requires a capacitor of 1nF C403 at pin29. PLL 1 Phase Detector The phase detector is a standard one using switched current sources. It compares the middle of H-sync. with a fixed point on the oscillator saw-tooth voltage. The PLL loop filter C401, C402, R409 is connected to Pin26. PLL2 Phase Detector The PLL2 detector thus compensates for the delay in the external H-deflection circuit by adjusting the phase of the HDRV output pulses. The phase between H-flyback and H-sync can be controlled at pin30. X-ray Protection The X-ray protection input pin2 provides a voltage detector with a precise threshold. If the voltage exceeds this threshold for a certain time, an internal latch switches the whole IC into protection mode. In this mode several pins are forced into defined states: Pin6 (BDRV) is floating Pin8 (HDRV) is floating Pin12, 13 ( VOUT 12, 13) are floating Vertical Oscillator The vertical free -running frequency is determined by the resistor C613 at pin24. Usually the free-running frequency should be lower than the minimum trigger frequency. ViewSonic Corporation 11 Confidential - Do Not Copy E70f-5_E70fB-5_E70fSB-5

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4-2
DEFLECTION CIRCUIT
The deflection circuit is achieved by a high performance and efficient solution IC 401 (TDA4841) for this
monitor. The concept is fully DC controllable and can be used in applications with a micro-controller solutions.
The TDA4841 provides sync. Processing with full auto sync. Capability, a flexible SMPS block and an extensive
set of geometry control facilities. Further the IC generates the drive waveforms for DC coupled vertical boosters
to the TDA4863.
Horizontal Oscillator
The oscillator is of the relaxation type and requires a capacitor of 1nF C403 at pin29.
PLL 1 Phase Detector
The phase detector is a standard one using switched current sources. It compares the middle of H-sync. with a
fixed point on the oscillator saw-tooth voltage.
The PLL loop filter C401, C402, R409 is connected to Pin26.
PLL2 Phase Detector
The PLL2 detector thus compensates for the delay in the external H-deflection circuit by adjusting the phase of
the HDRV output pulses. The phase between H-flyback and H-sync can be controlled at pin30.
X-ray Protection
The X-ray protection input pin2 provides a voltage detector with a precise threshold. If the voltage exceeds this
threshold for a certain time, an internal latch switches the whole IC into protection mode. In this mode several
pins are forced into defined states:
Pin6 (BDRV) is floating
Pin8 (HDRV) is floating
Pin12, 13 ( VOUT 12, 13) are floating
Vertical Oscillator
The vertical free –running frequency is determined by the resistor C613 at pin24. Usually the free-running
frequency should be lower than the minimum trigger frequency.
ViewSonic Corporation
Confidential – Do Not Copy
E70f-5_E70fB-5_E70fSB-5
11