A common application of the TRF1208 is to drive a high-speed ADC, such as the ADC12DJ5200RF or AFE7950 that have differential input. Conventionally, passive baluns are used to drive Gsps ADCs because of nonavailability of high-bandwidth, linear amplifiers. The TRF1208 is an active balun that has excellent bandwidth flatness, gain, and phase imbalance comparable to or exceeding costly passive baluns.

Figure 8-1 shows a typical interface circuit for the ADC12DJ5200RF. Depending on the ADC and system requirement, this circuit can be simplified or can be more complex.

Figure 8-1 Interfacing With the ADC12DJ5200RF

The figure shows two sections of the circuit between the driver amp and the ADC: namely, the matching pad (or attenuator pad) and the antialiasing filter. Use small, form-factor, RF-quality, passive components for these circuits. The output swing of the TRF1208 is designed to drive these ADCs full-scale, while at the same time not overdrive the device This functionality avoids the need for any voltage limiting device at the ADC.

The following figures show typical interface circuits for AFE7950 RX and TX chains in which TRF1208 is the S2D and D2S amplifier, respectively.

A. AFE matching network – component type (whether L or C) and values depend on the channel (A, B, C, D, FB1, FB2) and frequency band.

Figure 8-2 Interfacing With the AFE7950 RX

A. AFE matching network – component type (whether L or C) and values depend on the channel (A, B, C, D) and frequency band.

Figure 8-3 Interfacing With the AFE7950 TX