Splitterminering

Splitterminering, or split termination, is a technique used in high-speed digital and RF transmission to terminate a transmission line by placing two resistors in series across the line, with the midpoint connected to a reference voltage. The aim is to provide the line with its characteristic impedance while enabling a bias path for the signal.

In a typical implementation, two resistors R1 and R2 are chosen so that their parallel combination equals the line impedance Z0 (i.e., R1 ∥ R2 = Z0). When R1 = R2, each resistor equals 2Z0; for a 50 Ω line, two 100 Ω resistors are used. The center tap is connected to a DC bias (often Vcc or a reference) to set the logic level, resulting in a Thevenin termination. The drive sees the correct impedance, and the bias ensures proper quiescent levels without relying on the source or receiver alone.

Advantages include stable impedance matching with relatively low loading and the ability to set a defined DC level. Limitations include sensitivity to resistor tolerances and to temperature drift; the bias network must be designed so it does not unduly load the signal or conflict with the driver’s own biasing.

Applications include backplane and memory interfaces, clock lines, and other high-speed digital interconnections where preserving signal integrity is important.

See also: Thevenin termination, parallel termination, series termination, impedance matching.