LM6182AMN National Semiconductor, LM6182AMN Datasheet - Page 19

• Manufacturer Part Number: LM6182AMN
• Description: Dual 100 mA Output/ 100 MHz Current Feedback Amplifier
• Manufacturer: National Semiconductor

Typical Applications
POWER SUPPLY BYPASSING AND LAYOUT
CONSIDERATIONS
A fundamental requirement for high-speed amplifier design
is adequate bypassing of the power supply. It is critical to
maintain a wideband low-impedance to ground at the ampli-
fiers supply pins to insure the fidelity of high speed amplifier
transient signals. 0.1 µF ceramic bypass capacitors at each
supply pin are sufficient for many applications. Typically
10 µF tantalum capacitors are also required if large current
transients are delivered to the load. The bypass capacitors
should be placed as close to the amplifier pins as possible,
such as 0.5" or less.
Applications requiring high output power, cable drivers for
example, cause increased internal power dissipation. Inter-
nal power dissipation can be minimized by operating at re-
duced power supply voltages, such as
Optimum heat dissipation is achieved by using wide circuit
board traces and soldering the part directly onto the board.
Large power supply and ground planes will improve power
dissipation. Safe Operating Area (S.O.A.) is determined us-
ing the Maximum Power Derating Curves.
The 16-pin small outline package (M) has 5 V− heat sinking
pins that enable a junction-to-ambient thermal resistance of
70˚C/W when soldered to 2 in
sinking pin is located on each corner of the package for ease
of layout. This allows high output power and/or operation at
elevated ambient temperatures without the additional cost of
an integrated circuit heat sink. If the heat sinking capabilities
FIGURE 10. Resistive Isolation of C
Fidelity Pulse Response. R
Increased to Maintain A
Response Characteristics.
10A
10B
V
2
= −1 and Improve Pulse
1 oz. copper trace. A V− heat
f
and Rs Could Also Be
(Continued)
L
±
5V.
Provides Higher
DS011926-35
DS011926-34
19
of the S.O. package are not needed, pin 4 and at least one
of pins 1,8,9, or 16 must be connected to V− for proper op-
eration.
Figure 11 shows recommended copper patterns used to dis-
sipate heat from the LM6182.
CROSSTALK REJECTION
The LM6182 has an excellant crosstalk rejection value of
62 dB at 10 MHz. This value is made possible because the
LM6182 amplifiers share no common circuitry other than the
supply. High frequency crosstalk that does appear is prima-
rily caused by the magnetic and capacitive coupling of the in-
ternal bond wires. Bond wires connect the die to the package
lead frame. The amount of current flowing through the bond
wires is proportional to the amount of crosstalk. Therefore,
crosstalk rejection ratings will degrade when driving heavy
loads. Figure 12 and shows a 10 dB difference for two differ-
ent loads.
FIGURE 11. Copper Heatsink Layouts
16-pin S.O. (M)
8-pin DIP (N)
DS011926-36
DS011926-37
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