LMH6702-MIL Datasheet, PDF (15/19 Pages) Texas Instruments – 1.7-GHz Ultra-Low Distortion Wideband Op Amp

www.ti.com
Typical Application (continued)
8.2.4 Application Curve
100
90
80
70
60
50
40
30
20
10
0
1
25
0.05% SETTLING
20
15
0.1% SETTLING
R_S
10
5
0
10
100
1k
10k
C_L (pF)
LMH6702-MIL
SNOSD58 – JUNE 2017
A_V = -1
R_L = 1 kΩ
Figure 27. R_S and Settling Time vs C_L
9 Power Supply Recommendations
The LMH6702-MIL can operate off a single supply or with dual supplies as long as the input CM voltage range
(CMIR) has the required headroom to either supply rail. Supplies should be decoupled with low inductance, often
ceramic, capacitors to ground less than 0.5 inches from the device pins. The use of ground plane is
recommended, and as in most high speed devices, it is advisable to remove ground plane close to device
sensitive pins such as the inputs.
10 Layout
10.1 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 Frequent Faux Pas in Applying Wideband Current Feedback Amplifiers,
Application Note OA-15 (SNOA367). Texas Instruments suggests the following evaluation boards as a guide for
high frequency layout and as an aid in device testing and characterization. See Table 1 for details.
The LMH6702-MIL evaluation board(s) is a good example of high frequency layout techniques as a reference.
General high-speed, signal-path layout suggestions include:
• Continuous ground planes are preferred for signal routing with matched impedance traces for longer runs.
However, open up both ground and power planes around the capacitive sensitive input and output device
pins as shown in Figure 28. After the signal is sent into a resistor, parasitic capacitance becomes more of a
bandlimiting issue and less of a stability issue.
• Use good, high-frequency decoupling capacitors (0.1 μF) on the ground plane at the device power pins as
shown in Figure 28. Higher value capacitors (2.2 μF) are required, but may be placed further from the device
power pins and shared among devices. For best high-frequency decoupling, consider X2Y supply-decoupling
capacitors that offer a much higher self-resonance frequency over standard capacitors.
• When using differential signal routing over any appreciable distance, use microstrip layout techniques with
matched impedance traces.
• The input summing junction is very sensitive to parasitic capacitance. Connect any Rf, and Rg elements into
the summing junction with minimal trace length to the device pin side of the resistor, as shown in Figure 29.
The other side of these elements can have more trace length if needed to the source or to ground.
Copyright © 2017, Texas Instruments Incorporated
Product Folder Links: LMH6702-MIL
Submit Documentation Feedback
15