LT6557CDHC datasheet(8/12 Pages) LINER

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LT6557

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V+ B (Pin 9): Positive Supply Voltage of Blue Channel

Ampliﬁer. This pin is not internally connected to other

supply voltage pins and must be externally connected to

the supply voltage bus with proper bypassing for best

performance, see Power Supply Considerations.

OUT B (Pin 10): Blue Channel Output.

V+ G (Pin 11): Positive Supply Voltage of Green Channel

Ampliﬁer. This pin is not internally connected to other

supply voltage pins and must be externally connected to

the supply voltage bus with proper bypassing for best

performance, see Power Supply Considerations.

OUT G (Pin 12): Green Channel Output.

V+ R (Pin 13): Positive Supply Voltage of Red Channel

Ampliﬁer. This pin is not internally connected to other

supply voltage pins and must be externally connected to

Power Supply Considerations

The LT6557 is optimized to provide full video signal swing

output when operated from a standard 5V single supply.

Due to the supply current involved in ultrahigh slew rate

ampliﬁers like the LT6557, selection of the lowest workable

supply voltage is recommended to minimize heat genera-

tion and simplify thermal management. Temperature rise

at the internal devices (TJ) must be kept below 150°C

(SSOP package) or 125°C (DFN package), and can be

estimated from the ambient temperature (TA) and power

dissipation (PD) as follows:

TJ = TA + PD • 40°C/W for DFN package

TJ = TA + PD • 110°C/W for SSOP package

where PD = (IS + 0.5 • IO) • VS(TOTAL)

The latter equation assumes (conservatively) that the output

swing is small relative to the supply and RMS load current

(IO) is bidirectional (as with AC coupling).

the supply voltage bus with proper bypassing for best

performance, see Power Supply Considerations.

OUT R (Pin 14): Red Channel Output.

V+ (Pin 15): Positive Supply Voltage of Control Circuitry.

This pin is not internally connected to other supply voltage

pins and must be externally connected to supply voltage

bus with proper bypassing for best performance, see

Power Supply Considerations.

BCV (Pin 16): Bias Control Voltage. A resistor connected

between Pin 16 and Pin 2 (GND) will generate a DC voltage

bias at the inputs of the three ampliﬁers for AC coupling

application, see Programmable Input Bias.

Exposed Pad (Pin 17, DFN Package): Ground. This pad

must be soldered to PCB and is internally connected to

GND (Pin 2).

The grounds are separately pinned for each ampliﬁer to

minimize crosstalk.

Operation from split supplies can be accomplished by

connecting the LT6557 ground pins to the negative rail.

Since the ampliﬁer gain is referenced to its ground pins,

the actual signals are referenced to the negative rail, in

this case, and DC coupled applications need to take this

into consideration. With dual supplies, recommended

voltages range from nominal ±2.5V to ±3.3V.

The ultrahigh frequency (UHF) operating range of the

LT6557 requires that careful printed circuit layout prac-

tices be followed to obtain maximum performance. Trace

lengths between power pins and bypass capacitors should

be minimized (<0.1 inch) and one or more dedicated

ground planes should be employed to minimize parasitic

inductance. Poor layout or breadboarding methods can

seriously impact ampliﬁer stability, frequency response

and crosstalk performance. A 2.2µF and a 10µF bypass

capacitor is recommended for the LT6557supply bus, plus

a 10nF high frequency bypass capacitor at each individual

power pin.

PIN FUNCTIONS

APPLICATIONS INFORMATION

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