8-12

Application Information

The CA1391 and CA1394 contain the oscillator, phase

detector, and predriver sections necessary for the television

horizontal oscillator and AFC loop.

The oscillator is an RC type with Terminal 7 used to control the

capacitor connected from Terminal 7 to ground charges through

an external resistance connected between Terminals 6 and 7. As

soon as the voltage at Terminal 7 exceeds the potential set at the

that exceeds the bias set at Terminal 8. By adjusting the poten-

tial at Terminal 8, the duty cycle at the pre-drive output (Termi-

nal 1) may be changed. The phase detector is isolated from the

and the sawtooth waveform at Terminal 4, which is derived from

the horizontal flyback pulse. If there is no phase difference

between the sync and sawtooth, equal currents flow in the col-

for balanced conditions. When a phase offset occurs, current

flows either in or out of Terminal 5. In circuit applications, this

terminal is connected to Terminal 7 through an external low

pass filter, thereby controlling the oscillator.

POSITIVE PULSE WIDTH AT TERMINAL 1 (

µs)

70

60

50

40

30

20

10

0

2.0

2.5

3.0

3.5

4.0

4.5

5.0

FREE RUNNING FREQUENCY = 15734Hz

FIGURE 2. DUTY CYCLE AT THE PRE-DRIVE OUTPUT (TERMINAL

1) AS IT IS AFFECTED BY THE INPUT AT TERMINAL 8

87

6

5

4

3

2

1

CA1394

2

470

µF

0.47

µF

0.01

µF

3k

Ω

620

Ω

24V

V+

470pF

120k

Ω

6800pF

14k

Ω

2.7k

Ω

2.4k

Ω

1.5k

Ω

4k

Ω

10W

0.001

µF

+150V

270

Ω

1.2k

Ω

0.0027

µF

150k

Ω

8.2k

Ω

0.1

µF

0.1

µF

390k

Ω

3.9k

Ω

22

Ω

7.5k

Ω

SYNC

5

µs

10

µs

FIGURE 3. TYPICAL CIRCUIT APPLICATION

CA1391, CA1394