GB4600 Ver la hoja de datos (PDF) - Gennum -> Semtech

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GB4600

Monolithic Unity Gain Video Buffer

Gennum -> Semtech 

VIDEO INPUT

+5V

0.1

10K

3

1

27

7 GB4600 4

TALLY OUT

GX4201

VIDEO OUT

TALLY OUT

GX4201

VIDEO OUT

8

2

5

75

*R-SET

CL

0.1

TALLY OUT

GX4201

VIDEO OUT

-5V

-5V

All resistors are in ohms, all capacitors in microfarads unless otherwise stated

* The current will be maximum if the pin 5 is left open circuit. Any value of resistance from pin 5 to -VEE will reduce the current. The minimum current

(50% of max.) will occur when R-SET = 0 Ω.

TYPICAL APPLICATION CIRCUIT

The circuit shown above uses the GB4600 as an input For other applications, the ENABLE input on the GB4600

buffer driving several GX4201 video crosspoint ICs.

may be controlled by any TTL or 5 volt CMOS device.

The GB4600 is capable of driving loads up to 100 pF to

a -3 dB bandwidth of 80 MHz. For lighter loads, the

bandwidth is extended to over 100 MHz.

A unique feature of the GB4600 is that its current drain

can be reduced by adjusting the value of the resistor on

the I-SET input, pin 5.

Capacitor CL is used to shape the response in conjunction

with the 27 Ω series resistor from pin 4. The value shown

will give a -1 dB response at 100 MHz with a total load

capacitance (fixed plus actual) of 47 pF.

In order to disable the GB4600, pin 1 is driven from the

TALLY outputs of the GX4201s. When all crosspoints are

OFF, the voltage on pin 1 will be 0 volts, disabling the

GB4600. Whenever any crosspoint is selected, the

voltage on pin 1 rises to +5 volts and turns on the buffer.

This configuration minimizes the current drain when a

group of crosspoints are turned off.

If R-SET is made zero ohms (a direct connection to -VEE)

then the supply current drops 50% from 36 mA to 18 mA.

A reduced current will reduce the bandwidth as shown

in Figure 3. For values of RS = 27 Ω and CL = 47 pF, the

-1 dB bandwidth shrinks from 100 MHz at maximum

current to 80 MHz at minimum current.

As with any high frequency circuit, careful board layout

with ample ground plane is critical.

+5V

CHIP ENABLE

VIDEO INPUT

0.1

10 K

+5V

0.1

3

1

1

RS

7 GB4600 4

4

COMLINEAR

8

0.1

CLC110

8

2

5

75

CL

RL

10 K

5

0.1

0.1

-5V

-5V

Max. Min.

I-SET -5V

All resistors are in ohms, all capacitors in microfarads unless otherwise stated

TEST CIRCUIT

VIDEO OUT

(75Ω )

3

520 - 40 - 4

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