ML6423

6

FUNCTIONAL DESCRIPTION

The ML6423 single-chip dual video filter is intended for

low cost professional and consumer video applications.

Each of the two channels incorporates an input buffer

amplifier, a 6th-order lowpass filter, a 1st-order allpass

equalizer, sinx/x equalizer and an output 2X gain

amplifier capable of driving 75

W to ground. A third

output (B) is the sum of the A and C inputs and have the

identical output amplifier as the A and C channels.

The ML6423 can be driven by a DAC with RANGE down

to 0V. When RANGE is low the input range is 0.5V to

1.5V. When the input signal range is 0V to 0.1V, RANGE

should be tied high. In this case, an offset is added to the

input so that the output swing is kept between 0.5V to

2.5V. The output amplifier is capable of driving up to

24mA of peak current; therefore the output voltage should

not exceed 1.8V when driving 75

W to ground.

APPLICATION GUIDELINES

OUTPUT & INPUT CONSIDERATIONS

The dual filters have 2X gain. The circuit has 2X gain

(6dB) when connected to a 150W load, and 0dB gain

when driving a 75

W load via a 75W series output resistor.

The output may be either AC or DC coupled. For AC

coupling, the –3dB point should be 5Hz or less. There

must also be a DC path of

£500W to ground for output

biasing. The ML6423-5 provides higher sink current to

better drive AC coupled loads.

The input resistance is 4k

W. The input may be either DC

or AC coupled. (Note that each input sources 80 to 125µA

of bias current). The ML6423 is designed to be directly

driven by a DAC. For current output video DACs, a 75

W

or 150

W resistor to ground may need to be added to the

DAC output (filter input).

Figure 4. ML6423 AC Coupled DC Bias Test Circuit

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

RANGE

GNDA

NC

GNDB

GND

GNDC

NC

75

Ω

1

µF 100µF

0.1

µF

85

Ω

100

Ω

2.56k

Ω

1k

+

+

+

0.1

µF

100

µF

1nF

1nF

1nF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

1nF

1

µF

100

µF

75

Ω

85

Ω

100

Ω

75

Ω

2.56k

Ω

1k

Ω

+5V

FB2

FB1

DC

BIAS

INPUT SIGNAL

0.1

µF

1nF

INPUT

DECOUPLING

SUPPLY NOISE

CLAMPING

INPUT

TERMINATION

RESISTOR