One ADC-LD-BB board is included in the hardware kit with the GSPS analog-to-digital converter (ADC) reference boards. Since the analog inputs to the ADC1xDxx00RB are differential and most signal sources are single ended, these balun boards are generally used to achieve single-ended-to-differential conversion. In case both I- and Q- inputs are simultaneously driven with a similar signal, an additional balun board of the same type may be desired.
Incidentally, this balun board may also be used to do differential-to-single-ended conversion. For example, this balun board may be used when observing the DCLK± or RCOut± signal on a single-ended scope when exploring the autosync feature on the GSPS ADC reference boards.
ADC-LD-BB uses the B0430J50100AHF from Anaren®, which is designed for high performance and low cost. Since the input impedance of the GSPS ADCs are 100 Ω and the impedance of most signal generators are 50 Ω, its 1:2 impedance ratio is very convenient. The 10-pF capacitor at the input is recommended by Anaren for best performance. This balun is also a very good choice for driving the GSPS ADC sampling clock (CLK±).