lt6559cud-trpbf Linear Technology Corporation, lt6559cud-trpbf Datasheet - Page 8

• Manufacturer Part Number: lt6559cud-trpbf
• Description: Low Cost 5v/?5v 300mhz Triple Video Amplifier In 3mm X 3mm Qfn
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
APPLICATIONS INFORMATION
LT6559
GND (Pins 1, 4): Ground. Not connected internally.
–IN G (Pin 2): Inverting Input of G Channel Amplifi er.
+IN G (Pin 3): Noninverting Input of G Channel Amplifi er.
+IN B (Pin 5): Noninverting Input of B Channel Amplifi er.
–IN B (Pin 6): Inverting Input of B Channel Amplifi er.
⎯ E ⎯ N B (Pin 7): B Channel Enable Pin. Logic low to enable.
OUT B (Pin 8): B Channel Output.
V
or –5V.
Feedback Resistor Selection
The small-signal bandwidth of the LT6559 is set by the
external feedback resistors and the internal junction
capacitors. As a result, the bandwidth is a function of
the supply voltage, the value of the feedback resistor,
the closed-loop gain and the load resistor. Optimized for
±5V and single-supply 5V operation, the LT6559 has a
–3dB bandwidth of 300MHz at gains of +1, –1, or +2.
Refer to the resistor selection guide in the Typical AC
Performance table.
Capacitance on the Inverting Input
Current feedback amplifi ers require resistive feedback from
the output to the inverting input for stable operation. Take
care to minimize the stray capacitance between the output
and the inverting input. Capacitance on the inverting input
to ground will cause peaking in the frequency response
and overshoot in the transient response.
Capacitive Loads
The LT6559 can drive many capacitive loads directly when
the proper value of feedback resistor is used. The required
value for the feedback resistor will increase as load ca-
pacitance increases and as closed-loop gain decreases.
Alternatively, a small resistor (5Ω to 35Ω) can be put in
series with the output to isolate the capacitive load from
the amplifi er output. This has the advantage that the ampli-
8
–
(Pin 9): Negative Supply Voltage, Usually Ground
OUT G (Pin 10): G Channel Output.
⎯ E ⎯ N G (Pin 11): G Channel Enable Pin. Logic low to enable.
V
OUT R (Pin 13): R Channel Output.
⎯ E ⎯ N R (Pin 14): R Channel Enable Pin. Logic low to enable.
–IN R (Pin 15): Inverting Input of R Channel Amplifi er.
+IN R (Pin 16): Noninverting Input of R Channel Amplifi er.
Exposed Pad (Pin 17): V
fi er bandwidth is only reduced when the capacitive load
is present. The disadvantage is that the gain is a function
of the load resistance.
Power Supplies
The LT6559 will operate from single or split supplies from
±2V (4V total) to ±6V (12V total). It is not necessary to use
equal value split supplies, however the offset voltage and
inverting input bias current will change. The offset voltage
changes about 600µV per volt of supply mismatch. The
inverting bias current will typically change about 2µA per
volt of supply mismatch.
Slew Rate
Unlike a traditional voltage feedback op amp, the slew
rate of a current feedback amplifi er is dependent on the
amplifi er gain confi guration. In a current feedback ampli-
fi er, both the input stage and the output stage have slew
rate limitations. In the inverting mode, and for gains of 2
or more in the noninverting mode, the signal amplitude
between the input pins is small and the overall slew rate
is that of the output stage. For gains less than 2 in the
noninverting mode, the overall slew rate is limited by the
input stage.
The input slew rate of the LT6559 is approximately 600V/µs
and is set by internal currents and capacitances. The output
slew rate is set by the value of the feedback resistor and
+
(Pin 12): Positive Supply Voltage, Usually 5V.
–
. Must Be Soldered to the PCB.
6559f