an1186

ISL59440/41EVAL1 Evaluation Board
User’s Guide
®
Application Note
August 9, 2005
AN1186.1
Introduction
High Frequency Layout Considerations
The ISL59440/41EVAL1 evaluation board contains all the
circuitry needed to characterize critical performance
parameters of the ISL59440, ISL59441 single 4:1 MUXamplifier, over a variety of applications.
At frequencies of 500MHz and higher, circuit board layout
may limit performance. The following layout guidelines are
implemented on the evaluation board;
The ISL59440, ISL59441 are single-output, gain-selectable
4:1 MUX-amps. The unity- gain bandwidths are 400MHz for
the ISL59440 and 900 MHz for the ISL59441. Each contain
a common set of logic inputs for channel selection (S0, S1)
three-state output control (HIZ) and an enable control input
that powers down the device.
The evaluation board circuit and layout is optimized for
either 50Ω or 75Ω terminations, and implements a basic
single 4:1 video MUX-amp. The board is supplied with 75Ω
input signal terminations and a 75Ω back-termination
resistor on each of the 3 outputs, making it suitable for
driving video cable. The user has the option of replacing the
75Ω resistors with 50Ω resistors for other applications. The
control lines contain 50Ω resistors to match the 50Ω output
impedance of high speed pulse generators. Control line
termination resistors are recommended for rise and fall times
under 10ns to minimize unwanted transients. If DC is used
for the control logic, the resistors may be removed; or the
applied DC voltage can reduced to 2.5V to reduce the
dissipation in the termination resistor.
The layout contains component options to include an output
series resistor (RS) followed by a parallel resistor (RL)
capacitor (CL) network to ground. This option allows the user
to select several different output configurations. Examples
are shown in Figures 2A, 2B, and 2C. The evaluation board
is supplied with the 75Ω back termination resistors shown in
Figure 2C.
• No series connected vias are used in signal I/O lines, as
they can add unwanted inductance.
• Signal trace lengths are minimized to reduce transmission
line effects and the need for strip-line tuning of the signal
traces.
• High frequency decoupling caps are placed as close to the
device power supply pin as possible - without series vias
between the capacitor and the device pin.
Power Sequencing
Proper power supply sequencing is -V first, then +V. In
addition, the +V and -V supply pin voltage rate-of-rise must
be limited to ±1V/µs or less. The evaluation board contains
parallel-connected low VON Shottky diodes on each supply
terminal to minimize the risk of latch up due to incorrect
sequencing. In addition, extra 10µF decoupling capacitors
are added to each supply to aid in reducing the applied
voltage rate-of-rise.
Reference Documents
1. ISL59440 Data Sheet, FN7459
2. ISL59441 Data Sheet, FN7458
EN0
S0
EN1
IN0
IN1
Amplifier Performance and Output
Configurations
DECODE
EN2
The ISL59440, ISL59441 output amplifier is externally gainselectable with the non-inverting input directly coupled to the
4:1 MUX output. The inverting input is pinned out to the
evaluation board. Resistor RF is set to the value shown in
Figure 2D, and in conjunction with the amplifier internal
capacitance, provides optimum frequency response with
minimal gain peaking. The output amplifier is ideally suited
for driving high impedance high speed selectable-gain
buffers when gain compensation is needed. GBW decreases
slightly at the lower output load impedances typical of backterminated cable driving applications. Reference data sheets
for additional performance data.
1
• Signal I/O lines are the same lengths and widths to match
propagation delay and trace parasitics.
S1
EN3
IN2
+
OUT
IN3
AMPLIFIER BIAS
HIZ
ENABLE
FIGURE 1. ISL59440, ISL59441 FUNCTIONAL BLOCK
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Application Note 1186
TABLE 1. LOGIC TABLE
VIN
50Ω
OR
75Ω
ISL59440, ISL59441
RS, 0Ω
+
*Cb1
~0.5pF
RF
S0
S1
HIZ
ENABLE
OUT
0
0
0
0
IN0
1
0
0
0
IN1
0
1
0
0
IN2
1
1
0
0
IN3
-
-
-
1
Power-down
-
-
1
-
High Z
*Cb2
~3pF
CL
1.5pF
RL
500Ω
* Cb1, Cb2 are approximate PCB trace capacitances.
+
RF
+
RF
475Ω
Cb1
RL
~0.5pF
50Ω
OR
75Ω
50Ω
OR
75Ω
FIGURE 2B. TEST CIRCUIT FOR 50Ω OR 75Ω TERMINATIONS
TEST
EQUIPMENT
ISL59440, ISL59441
50Ω
OR
75Ω
50Ω
OR
75Ω
RS
* Cb1 is approximate PCB trace capacitance.
FIGURE 2A. TEST CIRCUIT WITH OPTIMAL OUTPUT LOAD
VIN
TEST
EQUIPMENT
ISL59440, ISL59441
VIN
RS
50Ω OR 75Ω
Cb1
~0.5pF
50Ω
OR
75Ω
PART #
RF VALUE
ISL59440
332Ω
ISL59441
301Ω
* Cb1 is approximate PCB trace capacitance.
FIGURE 2C. BACK-TERMINATED TEST CIRCUIT FOR CABLE
APPLICATION
FIGURE 2D. RF TABLE FOR FIGURE 2 CIRCUITS
ISL59440/41EVAL1 Top View
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Application Note 1186
ISL59440/41EVAL1 Schematic Diagram
JENBAR
1 NIC
ISL59440
ISL59441
2 IN0
IN0
R9
75Ω
IN1
ENBAR
EN 16
HIZ 15
3 NIC
IN- 14
4 IN1
OUT 13
JHIZ
R12 - 49.9Ω
HIZ
RF
R14 - 49.9Ω
OUT
R5 - 75Ω
R2
75Ω
5 GND
IN2
R10
75Ω
V+ 12
6 IN2
V- 11
7 NIC
S1 10
JSO
S1
R18 - 50Ω
S0 9
8 IN3
IN3
C9
R20
D1
R1
75Ω
SO
R19 - 50Ω
JSO
C7
C2
C1
C3
10uF 0.1uF 10nF 1nF
+
D2
GND. V-
+
C8
C5
C4
C6
10uF 0.1uF 10nF 1nF
V+
ISL59440/41EVAL1 Components Parts List
DEVICE #
DESCRIPTION
COMMENTS
C7, C8
CAP, SMD, 0603, 1000pF, 25V, 10%, X7R
Power Supply Decoupling
C1, C4
CAP, SMD, 0603, 0.01µF, 25V, 10%, X7R
Power Supply Decoupling
C2, C5
CAP, SMD, 0603, 0.1µF, 25V, 10%, X7R
Power Supply Decoupling
C3, C6
CAP, SMD, 0805, 10µF, 6.3V, 10%, X5R
Power Supply Decoupling
D1, D2
Diode-Shottky, 2 Pin, 45V, 7.5A
MBR0550T (Motorola) Reverse Polarity Protection
R1, R2, R5, R9, R10
Resistor, SMD, 0603, 75Ω, 1/10W, 1%,
Signal Input/output Termination
R12, R14, R18, R19.
Resistor, SMD, 0603, 49.9Ω, 1/16W, 1%,
Logic Input Termination
RF - ISL59440
Resistor, SMD, 0603, 332Ω, 1/10W, 1%
Feedback Resistor
RF - ISL59441
Resistor, SMD, 0603, 301Ω, 1/10W, 1%
Feedback Resistor
C9
CAP, SMD, 0603
Optional, not populated
R20
Resistor, SMD, 0603
Optional, not populated
U1
ISL59440/41 - 400/900 MHz MULTIPLEXING
AMPLIFIER, 16PIN, QSOP
Device Under Test
Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to
verify that the Application Note or Technical Brief is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
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