LMH6551Q-Q1 Datasheet, PDF (19/25 Pages) National Semiconductor (TI) – LMH6551Q Differential, High Speed Op Amp

LMH6551Q
www.ti.com
SNOSB95E – NOVEMBER 2011 – REVISED MARCH 2013
Figure 37 shows the maximum power dissipation vs. ambient temperature for the VSSOP-8 package when
mounted on a 4 layer JEDEC board.
1.8
VSSOP
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-40 -20 0 20 40 60 80 100 120 140
TA(°C)
Figure 37. Maximum Power Dissipation vs. Ambient Temperature
At high ambient temperatures, the LMH6551Q's quiescent power dissipation approaches the maximum power
shown in Figure 37, when operated close to the maximum operating supply voltage of 11V. This leaves little
room for additional load power dissipation. In such applications, any of the following steps can be taken to
alleviate any junction temperature concerns:
• Reduce the total supply voltage
• Reduce θ_JA by increasing heatsinking possibly by either increasing the PC board area devoted to heatsinking
or forced air cooling or both
• Reduce maximum ambient temperature
ESD PROTECTION
The LMH6551Q is protected against electrostatic discharge (ESD) on all pins. The LMH6551Q will survive 2000V
Human Body model and 200V Machine model events. Under normal operation the ESD diodes have no effect on
circuit performance. There are occasions, however, when the ESD diodes will be evident. If the LMH6551Q is
driven by a large signal while the device is powered down the ESD diodes will conduct. The current that flows
through the ESD diodes will either exit the chip through the supply pins or will flow through the device, hence it is
possible to power up a chip with a large signal applied to the input pins.
BOARD LAYOUT
The LMH6551Q is a very high performance amplifier. In order to get maximum benefit from the differential circuit
architecture board layout and component selection is very critical. The circuit board should have low a
inductance ground plane and well bypassed broad supply lines. External components should be leadless surface
mount types. The feedback network and output matching resistors should be composed of short traces and
precision resistors (0.1%). The output matching resistors should be placed within 3-4 mm of the amplifier as
should the supply bypass capacitors.
The LMH6551Q is sensitive to parasitic capacitances on the amplifier inputs and to a lesser extent on the
outputs as well. Ground and power plane metal should be removed from beneath the amplifier and from beneath
R_F and R_G.
With any differential signal path symmetry is very important. Even small amounts of asymmetry will contribute to
distortion and balance errors.
EVALUATION BOARD
Texas Instruments offers evaluation board(s) to aid in device testing and characterization and as a guide for
proper layout. Generally, a good high frequency layout will keep power supply and ground traces away from the
inverting input and output pins. Parasitic capacitances on these nodes to ground will cause frequency response
peaking and possible circuit oscillations (see Application Note OA-15 for more information).
Copyright © 2011–2013, Texas Instruments Incorporated
Product Folder Links: LMH6551Q
Submit Documentation Feedback
19