ISL59448IAZ-T7 Intersil, ISL59448IAZ-T7 Datasheet - Page 11

• Manufacturer Part Number: ISL59448IAZ-T7
• Description: IC AMP MUX 2:1 500MHZ 24-QSOP
• Manufacturer: Intersil

Specifications of ISL59448IAZ-T7

• Applications: 2:1 Multiplexer-Amplifier
• Number Of Circuits: 3
• -3db Bandwidth: 570MHz
• Slew Rate: 1600 V/µs
• Current - Supply: 31mA
• Current - Output / Channel: 180mA
• Mounting Type: Surface Mount
• Package / Case: 24-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AC Test Circuits
Figure 27C and 27D illustrate the optimum output load for
testing AC performance at 500Ω and 150Ω loads. Figure
27E illustrates the optimun output load for 50Ω and 75Ω
cable-driving.
FIGURE 27C. 500
FIGURE 27D. 150
FIGURE 27E. BACKLOADED TEST CIRCUIT FOR 75Ω VIDEO
AC Test Circuits
FIGURE 27A. TEST CIRCUIT WITH OPTIMAL OUTPUT LOAD
V
50Ω,or
75Ω
V
V
V
IN
IN
IN
IN
50Ω
75Ω
50Ω
50Ω
75Ω
or
or
FIGURE 27B. INTER-STAGE APPLICATION CIRCUIT
*C
*C
*C
L
V
ISL59448
L
ISL59448
L
ISL59448
ISL59448
IN
Includes PCB trace capacitance
Includes PCB trace capacitance
50Ω
75Ω
Includes PCB trace capacitance
*C
or
CABLE APPLICATION
L
Includes PCB trace capacitance
L
L
L
L
Ω
Ω
CRIT
ISL59448
CRIT
CRIT
CRIT
TEST CIRCUIT WITH 50Ω LOAD
TEST CIRCUIT WITH 50Ω LOAD
C
*C
1.1pF
*C
1.1pF
L
*C
1.1pF
L
L
475Ω
118Ω
50Ω or 75Ω
L
R
R
R
R
S
S
S
S
*C
1.1pF
L
11
C
56.2Ω
86.6Ω
S
L
CRIT
500Ω, or
150Ω
R
L
EQUIPMENT
EQUIPMENT
EQUIPMENT
50Ω
50Ω
50Ω or 75Ω
V
500Ω, or
75Ω
TEST
TEST
TEST
R
OUT
L
ISL59448
General
Key features of the ISL59448 include a fixed gain of 2,
buffered high impedance analog inputs and excellent AC
performance at output loads down to 150Ω for video cable-
driving. The current feedback output amplifiers are stable
operating into capacitive loads.
For the best isolation and crosstalk rejection, all GND pins
and NIC pins must connect to the GND plane.
AC Design Considerations
High speed current-feed amplifiers are sensitive to
capacitance at the inverting input and output terminals. The
ISL59448 has an internally set gain of 2, so the inverting
input is not accessible. Capacitance at the output terminal
increases gain peaking (Figure 1) and pulse overshoot
(Figures15 thru 18). The AC response of the ISL59448 is
optimized for a total capacitance of 1.1pF over the load
range of 150Ω to 500Ω.
PC board trace length should be kept to a minimum in order
to minimize output capacitance and prevent the need for
controlled impedance lines. At 500MHz trace lengths
approaching 1” begin exhibiting transmission line behavior
and may cause excessive ringing if controlled impedance
traces are not used. Figure 27A shows the optimum inter-
stage circuit when the total output trace length is less than
the critical length of the highest signal frequency.
For applications where pulse response is critical and where
inter-stage distances exceed L
Figure 27B is recommended. Resistor R
capacitance seen by the amplifier output to the trace
capacitance from the output pin to the resistor. Therefore,
R
possible. For inter-stage distances much greater than L
the back-loaded circuit shown in Figure 27E should be used
with controlled impedance PCB lines, with R
to the controlled impedance.
For applications where inter-stage distances are long, but
pulse response is not critical, capacitor C
low values of R
overshoot. This approach avoids the need for the large gain
correction required by the -6dB attenuation of the back-
loaded controlled impedance interconnect. Load resistor RL
is still required but can be 500Ω or greater, resulting in a
much smaller attenuation factor.
Control Signals
S0, S1, ENABLE, LE, HIZ - These are binary coded,
TTL/CMOS compatible control inputs. The S0, S1 pins select
the inputs. All three amplifiers are switched simultaneously
from their respective inputs. The ENABLE, LE, HIZ pins are
used to disable the part to save power, latch in the last logic
state and three-state the output amplifiers, respectively. For
Application Information
S
should be placed as close to the ISL59448 output pin as
S
to form a low-pass filter to dampen pulse
CRIT,
the circuit shown in
S
S
constrains the
can be added to
S
and R
March 29, 2006
L
FN6160.2
equal
CRIT,