STV9381

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1

PIN FUNCTIONS

2

FUNCTIONAL DESCRIPTION

The STV9381 is a vertical deflection circuit operating in class D. The class D is a modulation method

where the output transistors work in switching mode at high frequency. The output signal is restored by fil-

tering the output square wave with an external LC filter. The major interest of this IC is the low power dis-

sipation 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 end-

ed signal. This sawtooth is amplified and applied as a current to the deflection yoke. This current is meas-

ured 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 “in-

ternal 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.

Pin

Number

Name

Function

Negative supply

Negative supply

Negative supply

4

OUT

PWM Output

5

CFLY+

Flyback capacitor

6

CFLY-

Flyback capacitor

7

BOOT

Bootstrap capacitor

8

VREG

Internal voltage regulator

9

FEEDCAP

Feed-back integrating capacitor

10

FREQ

Frequency setting resistor

11

SGND

Signal Ground

12

IN-

Error amplifier inverting input

13

IN+

Error amplifier non-inverting input

14

EA out

Error amplifier output

15

Positive supply

16

Positive Power supply

17

-VccPOW

Negative Power supply

18

Negative supply

19

Negative supply

20

Negative supply

2