LME49600

www.ti.com

SNAS422E – JANUARY 2008 – REVISED APRIL 2013

Unity gain stability is preserved when the LME49600 is placed in the feedback loop of most general-purpose or

precision op amps. When the LME46900 is driving high value capacitive loads, the BW pin should be connected

speed or fast-settling operational amplifiers. This preserves their stability and the ability to faithfully amplify high

frequency, fast-changing signals. Stability is ensured when pulsed signals exhibit no oscillations and ringing is

minimized while driving the intended load and operating in the worst-case conditions that perturb the

LME49600’s phase response.

HIGH FREQUENCY APPLICATIONS

The LME49600’s wide bandwidth and very high slew rate make it ideal for a variety of high-frequency open-loop

applications such as an ADC input driver, 75

Ω stepped volume attenuator driver, and other low impedance loads.

Circuit board layout and bypassing techniques affect high frequency, fast signal dynamic performance when the

LME49600 operates open-loop.

A ground plane type circuit board layout is best for very high frequency performance results. Bypass the power

placed as close as possible to the respective pins.

Source resistance can affect high-frequency peaking and step response overshoot and ringing. Depending on

the signal source, source impedance and layout, best nominal response may require an additional resistance of

25

Ω to 200Ω in series with the input. Response with some loads (especially capacitive) can be improved with an

output series resistor in the range of 10

Ω to 150Ω.

THERMAL MANAGEMENT

Heatsinking

For some applications, the LME49600 may require a heat sink. The use of a heat sink is dependent on the

maximum LME49600 power dissipation and a given application’s maximum ambient temperature. In the TO-263

package, heat sinking the LME49600 is easily accomplished by soldering the package’s tab to a copper plane on

Through the mechanisms of convection, heat conducts from the LME49600 in all directions. A large percentage

moves to the surrounding air, some is absorbed by the circuit board material and some is absorbed by the

copper traces connected to the package’s pins. From the PCB material and the copper, it then moves to the air.

Natural convection depends on the amount of surface area that contacts the air.

If a heat conductive copper plane has perfect thermal conduction (heat spreading) through the plane’s total area,

the temperature rise is inversely proportional to the total exposed area. PCB copper planes are, in that sense, an

aid to convection. These planes, however, are not thick enough to ensure perfect heat conduction. Therefore,

eventually a point of diminishing returns is reached where increasing copper area offers no additional heat

conduction to the surrounding air. This is apparent in Figure 30 as the thermal resistance reaches an asymptote

compared to 1 oz. copper. Beyond 1oz or 2oz copper plane areas, external heat sinks are required. Ultimately,

the 1oz copper area attains a nominal value of 20°C/W junction to ambient thermal resistance (

air flow.

Copyright © 2008–2013, Texas Instruments Incorporated

Submit Documentation Feedback

13

Product Folder Links: LME49600