551600075-001 National Semiconductor, 551600075-001 Datasheet - Page 22

• Manufacturer Part Number: 551600075-001
• Description: BOARD FOR SOIC LMH6612/19
• Manufacturer: National Semiconductor
• Series: WEBENCH® Buildit Boardr

Specifications of 551600075-001

• Channels Per Ic: 2 - Dual
• Amplifier Type: General Purpose
• Board Type: Bare (Unpopulated)
• Utilized Ic / Part: LMH6612, LMH6619
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Operating Temperature: -
• Output Type: -
• Current - Output / Channel: -
• Voltage - Supply, Single/dual (±): -
• -3db Bandwidth: -
• Slew Rate: -
• Current - Supply (main Ic): -

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Because SINAD compares all undesired frequency compo-
nents with the input frequency, it is an overall measure of an
ADC’s dynamic performance. The following sections will dis-
cuss the three different ADC driver architectures in detail.
SINGLE TO SINGLE ADC DRIVER
This architecture has a single-ended input source connected
to the input of the op amp and the single-ended output of the
op amp is then fed to the single-ended input of the ADC. The
low noise of only 10 nV/
make the LMH6611 an excellent choice for driving the 12-bit
ADC121S101 500 KSPS to 1 MSPS ADC, which has a suc-
cessive approximation architecture with internal sample and
hold circuits.
in a 2nd order multiple-feedback with gain of −1 (inverting)
configuration, driving an ADC121S101. The inverting config-
When the op amp and the ADC are using the same supply, it
is important that both devices are well bypassed. A 0.1 µF
ceramic capacitor and a 10 µF tantalum capacitor should be
located as close as possible to each supply pin. A sample
layout is shown in
C6) and the 10 µF capacitors (C11 and C5) are located very
close to the supply pins of the LMH6611 and the AD-
C121S101.
The following are recommendations for the design of PCB
layout in order to obtain the optimum high frequency perfor-
mance:
Output/ADC Input
Amplifier
4
Figure 2
Figure
shows the schematic of the LMH6611
TABLE 1. Performance of the LMH6611 Combined with the ADC121S101
5. The 0.1 µF capacitors (C13 and
and a wide bandwidth of 345 MHz
SINAD
(dB)
70.2
FIGURE 4. Single to Single ADC Driver
SNR
(dB)
71.6
−75.7
THD
(dB)
22
uration is preferred over the non-inverting configuration, as it
offers more linear output response.
formance data of the LMH6611 combined with the AD-
C121S101. The ADC driver’s cutoff frequency of 500 kHz is
found from the equation:
The op amp’s gain is set by the equation:
•
•
•
•
•
SFDR
(dBc)
77.6
Place ADC and amplifier as close together as possible.
Put the supply bypassing capacitors as close as possible
to the device (<1”).
Utilize surface mount instead of through-hole components
and ground and power planes.
Keep the traces short where possible.
Use terminated transmission lines for long traces.
ENOB
11.4
ADC121S101 @ f = 200 kHz
Table 1
Notes
shows the per-
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