Circuito integrato STV9381 - ST

CLASS-D VERTICAL DEFLECTION AMPLIFIER FOR TV AND MONITOR APPLICATION
FEATURES

HIGH EFFICIENCY POWER AMPLIFIER NO HEATSINK SPLIT SUPPLY INTERNAL FLYBACK GENERATOR OUTPUT CURRENT TO 3 APP SUITABLE FOR DC COUPLING APPLICATION FEW EXTERNAL COMPONENTS PROTECTION AGAINST LOW Vcc

DESCRIPTION

Designed for monitors and TVs, the is a class-D vertical deflection booster assembled in PDIP20 Package. It operates with supplies to 18V, provides to 3 App output current to drive the yoke. The internal flyback generator avoids the need for an extra power supply.

-VCC OUT CFLY + CFLY BOOT VREG FEEDCAP FREQ

Pin Number Name -VCC OUT CFLY+ CFLYBOOT VREG FEEDCAP FREQ SGND ININ+ EA out +VCC +VCCPOW -VccPOW -VCC Negative supply Negative supply Negative supply PWM Output Flyback capacitor Flyback capacitor Bootstrap capacitor Internal voltage regulator Feed-back integrating capacitor Frequency setting resistor Signal Ground Error amplifier inverting input Error amplifier non-inverting input Error amplifier output Positive supply Positive Power supply Negative Power supply Negative supply Negative supply Negative supply Function

The is a vertical deflection circuit operating in class D. The class is a modulation method where the output transistors work in switching mode at high frequency. The output signal is restored by filtering the output square wave with an external LC filter. The major interest of this IC is the low power dissipation comparatively to traditional amplifiers operating in class AB, eliminating the need of an heatsink. Except for the output stage which uses the class D modulation, the circuit operation is similar to the one of a traditional linear vertical amplifier. A reference signal (sawtooth) has to be applied to the circuit which can accept a differential or single ended signal. This sawtooth is amplified and applied as a current to the deflection yoke. This current is measured by means of a low value resistor. The resulting voltage is used as a feed-back signal to guarantee the conformity of the yoke current with the reference input signal. The overvoltage necessary for a fast retrace is obtained with a chemical capacitor charged at the power supply voltage of the circuit. At the flyback moment this capacitor is connected in series with the output stage power supply. This method, used for several years with the linear vertical boosters and called "internal flyback" or "flyback generator", avoids the need of an additional power supply, while reducing the flyback duration. The circuit uses a BCD process that combines Bipolar, CMOS and DMOS devices. DMOS transistors are used in the output stage due to the absence of second breakdown.

VREG -VCC 100nF 8 Vref Flyback detection Flyback generator 5 6 CFLY+ CFLYBACK 100µF

IN+ 13 1k Input signal 12 EA out 1k 11 SGND FEEDCAP 4.7nF 9 Pins 1,2,3,18,19,20 10 FREQ 10k -VCC + _ Modulator Output drive