Signal-path switch for portable audio and sensor routing
The MAX14689EWL+T is a single DPDT (Double-Pole Double-Throw) analog switch from Analog Devices' Beyond-the-Rails™ series, designed for routing audio, analog sensor, or low-voltage signal paths in battery-powered equipment. The 450 mOhm max on-resistance keeps voltage drop across the switch below 1 mV at typical headphone currents, preserving signal integrity in the audio band. Channel-to-channel matching is held to 5 mOhm, so the left and right audio channels see nearly identical insertion loss — no channel imbalance.
The 110 MHz -3 dB bandwidth is well above the audio band and covers video up to VGA resolution; the switch passes composite video or high-speed data lines without visibly rolling off the edges. Crosstalk is specified at -100 dB at 100 kHz — a signal on one channel couples into the adjacent channel at 100 dB below the carrier, which is below the noise floor of most codec inputs. Turn-on time is 200 µs max, turn-off is 30 µs max. The 200 µs turn-on means the switch needs a 200 µs settling window after the control logic asserts the enable before the signal path is fully established — a pop-suppression circuit or a delayed enable in the codec driver handles the transient. Off-leakage is 100 nA max, which keeps the signal lines from drifting when the switch is open.
WLP package and board integration
Housed in a 9-WLP (1.26 x 1.26 mm) wafer-level package, the MAX14689EWL+T occupies roughly the area of a 0805 resistor. The 0.4 mm pitch BGA footprint demands a via-in-pad or microvia layout for the centre balls — a 4-layer board with laser-drilled vias is the standard approach. Channel capacitance is 25 pF per port — this capacitance loads the signal line and combines with the source impedance to form a low-pass filter. At a 50-ohm source impedance, the -3 dB corner from the switch alone is roughly 127 MHz, consistent with the 110 MHz bandwidth spec. Keep the trace capacitance between the source and the switch below 10 pF to avoid rolling off the bandwidth further.
Active production and compliance standing
The 9-WLP package is proprietary to this device; a board-level alternative would require a different footprint and a layout revision.