Deflection Circuit; The Oscillation And Deflection Control Integrated Circuit; Digital Signal Processor (Dsp); 1Bit D/A Converter (1Bit Dac) - NEC MultiSync FP1370 Service Manual

2. DEFLECTION CIRCUIT

2-1. The oscillation and deflection control integrated circuit

The oscillation and the deflection circuit is generated by IC501. IC501 has digital signal processor (DSP)
and generates variety of correction signals by calculations. The feature of IC501 are low tolerance and low
drift of temperature compared with current analog circuit. The functions of IC501 are Horizontal oscillation,
Vertical oscillation, Horizontal position control, Distortion correction, Dynamic focus control, Moire canceler,
and Convergence correction. These correction signals generated by DSP are converted to analog signal by
the D/A converter, and these signals are output from IC output terminal.

1) Digital Signal Processor (DSP)

The digital signal processor generates variety of correction signals by calculations based on MPU (IC801)
data. The DSP generate saw wave by MPU data. The signal, after the AGC in this saw wave, is moved to
the reference signal. This reference signal generates various correction signals. All the signal wave shape
formation inside DSP are done by the operation. The output signals from DSP are converted to analog
signal by the D/A converter, and then these signals are output from IC output terminal.
DATA
MPU

2) 1bit D/A converter (1bit DAC)

Most of the signals which are generated by DSP are output from 1 bit D/A converter. The 1bit D/A
converter is pulse width modulation (PWM) circuit which is operated with 25MHz internal clock signal. The
3.3Vp-p signal which is modulated by pulse width is output from the 1bit D/A converter output terminal.
This signal is integrated by integration circuit which is composed of resistor and capacitor and creates
vertical periodic wave. The vertical dynamic focus control, distortion correction, convergence correction
and moire canceler signals are output from the 1bit D/A converter.
V.sync
DSP
AGC
Reference
signal
(Fig. 2.1) Digital Signal Processor (DSP)
1bit D/A OUTPUT
3.3Vp-p
IC501
Vertical saw wave
Distortion correction wave
Moire cancel wave
Dynamic focus wave
Convergence correction wave
Integration circuit
Operated by 25MHz clock.
(Fig. 2.2) 1bit D/A converter
8-7
D/A
converter