ML6421 データシートの表示（PDF） - Micro Linear Corporation

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ML6421

Triple Phase and Sinx/x Equalized, Low-Pass Video Filter

Micro Linear Corporation 

ML6421

FUNCTIONAL DESCRIPTION

The ML6421 single-chip Triple Video Filter IC is intended

for consumer and low cost professional video

applications. Each of the three channels incorporates an

input buffer amplifier, a sixth order lowpass filter, a first

order allpass equalizer, Sinx/x equalizer and an output

amplifier capable of driving 75Ω to ground.

The ML6421 can be driven by a DAC with Range down to

0V. When Range is low the input and output signal range

is 0.5V to 2.5V. When the input signal includes 0V, 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 75Ω to ground.

APPLICATION GUIDELINES

OUTPUT CONSIDERATIONS

The triple filters have unity gain. The circuit has unity

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

gain when driving a 75Ω load via a 75Ω 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 -500Ω to ground for output

biasing.

INPUT CONSIDERATIONS

The input resistance is 4kΩ. The input may be either DC or

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

bias current). The ML6421 is designed to be directly

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

150Ω resistor to ground may need to be added to the DAC

output (filter input).

+5V

0.001µF

FB2

0.1µF 100µF

SUPPLY NOISE

CLAMPING

47Ω

INPUT

DECOUPLING

0.1µF

INC

INPUT SIGNAL = 2VP-P

85Ω

100µF DC

BIAS

INPUT

TERMINATION

FB1

OUTC

75Ω

1µF

3.1kΩ

1kΩ

1

GNDB

2

VINC

3

GND

1nF 4

GNDC

0.1µF

5

VCC

0.1µF

1nF 6

VCCC

7

VOUTC

0.1µF

1nF 8

VCCB

47Ω

47Ω

3.1kΩ

1µF 0.1µF

16

VINB

1kΩ

INB

1µF

85Ω

100µF

3.1kΩ

15

VINA

14

RANGE

13

GNDA

121nF

GND

11

VCCA

0.1µF

0.1µF

100µF

1kΩ

INA

85Ω

10

VOUTA

9

VOUTB

OUTA

75Ω

OUTB

75Ω

Figure 9. ML6421 AC Coupled DC Bias Test Circuit

8

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