LMH6644-MIL Datasheet, PDF (25/28 Pages) Texas Instruments – Low-Power, 130-MHz, 75-mA Rail-to-Rail Output Amplifier

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11 Layout
LMH6644-MIL
SNOSD65 – JUNE 2017
11.1 Layout Guidelines
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, "Frequent Faux Pas in Applying Wideband Current
Feedback Amplifiers", SNOA367, for more information). Texas Instruments suggests the following evaluation
boards as a guide for high-frequency layout and as an aid in device testing and characterization:
Table 1. Printed Circuit Board Layout And Component Values
DEVICE
LMH6644MA
LMH6644MT
PACKAGE
14-Pin SOIC
14-Pin TSSOP
EVALUATION BOARD PN
LMH730231
LMH730131
Another important parameter in working with high-speed and high-performance amplifiers is the component
values selection. Choosing external resistors that are large in value will effect the closed loop behavior of the
stage because of the interaction of these resistors with parasitic capacitances. These capacitors could be
inherent to the device or a by-product of the board layout and component placement. Either way, keeping the
resistor values lower, will diminish this interaction to a large extent. On the other hand, choosing very low value
resistors could load down nodes and will contribute to higher overall power dissipation.
11.2 Layout Example
Figure 59. LMH6644-MIL Layer 1
Figure 60. LMH6644-MIL Layer 2
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