LMH2832 Datasheet, PDF (35/46 Pages) Texas Instruments – LMH2832 Fully Differential, Dual, 1.1-GHz, Digital Variable-Gain Amplifier

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LMH2832
SBOS709A – JULY 2016 – REVISED JULY 2016
10.3 Do's and Don'ts
10.3.1 Do:
• Include a thermal analysis at the beginning of the project
• Use well-terminated transmission lines for all signals
• Maintain symmetrical input and output trace layouts
• Use solid metal layers for the power supplies
• Keep signal lines as straight as possible
10.3.2 Don't:
• Use a lower power-supply voltage than necessary
• Forget about the common-mode response of filters and transmission lines
• Rout digital line traces close to the analog signals and supply line traces
11 Power Supply Recommendations
The LMH2832 is designed to be used with a single supply with a range of 4.75 V to 5.25 V. The ideal supply
voltage is a 5.0-V total single-ended supply. If the supply is reduced to the minimum voltage, then the maximum
input and output voltage range is reduced by 0.25 V.
11.1 Split Supplies
Ideally, the LMH2832 uses a single-ended, 5-V supply, but the device can be operated on a split supply if
necessary. However, the digital logic is referenced to the GND pins, meaning that the logic reference shifts with
the GND supply if connected to a negative voltage and must be accounted for in the logic connections. In
general, the LMH2832 is not suggested to be operated with a split-supply configuration.
11.2 Supply Decoupling
Power-supply decoupling is critical to high-frequency performance. Onboard bypass capacitors are used on the
LMH2832EVM; however, the most important component of the supply bypassing is provided by the printed circuit
board (PCB). As illustrated in Figure 64, there are multiple vias connecting the LMH2832 power planes to the
power-supply traces. These vias connect the internal power planes to the LMH2832. Both V_CC and GND must be
connected to the internal power planes with several square centimeters of continuous plane in the immediate
vicinity of the amplifier. The capacitance between these power planes provides the bulk of the high-frequency
bypassing for the LMH2832.
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