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AN-1683 LMH7324 High Speed Comparator Evaluation Board (Rev. A)


This board is designed to demonstrate the LMH7324 quad comparator with RSPECL outputs. It will facilitate the evaluation of the LMH7324 configured as a window detector. The board detects the level of the incoming signal and presents the outcome in a 3-bit presentation. One bit indicates that the signal is below the lowest window level, another bit indicates that the signal is above the highest window level, and the third bit indicates that the incoming signal is just between both set levels. All three outputs are fed to SMA connectors mounted at the edge of the board. The impedance of the output track is 50Ω which makes it easy to connect these signals to any scope or analyzer by the use of a 50Ω coaxial cable. Each comparator of the LMH7324 has individual positive supplies for the input and output circuits. The negative supply is common for all input and output circuitry. This setup will work with a supply of ±2.5V as a minimum supply, with the window voltage centered at ground. If a setup with only one positive supply voltage is used, jumper J1 (see Figure 7) has to be placed between both positive supply connections. To examine the possibility of two separate supplies for the input and the output stage the jumper has to be removed and an extra supply has to be connected.