SPDT analog switch in SC-70-6 — what the key specs mean for your signal path
The MAX4730EXT+T is a single-pole double-throw (SPDT) analog switch from Analog Devices, packaged in a 6-lead SC-70-6 (SOT-363) footprint. It routes one common terminal to either of two outputs, with a 2:1 multiplexer/demultiplexer topology. The 5.5 Ohm max on-resistance (Ron) with 50 mOhm channel-to-channel matching means signal attenuation and distortion are low across the switch path — important for precision analog routing where a few milliohms of variance would shift a measurement.
Bandwidth, crosstalk, and switching speed — the RF/analog signal integrity story
A 300 MHz -3 dB bandwidth places this switch well above the needs of baseband audio or low-speed sensor multiplexing; it can pass a 100 MHz clock or a video signal with minimal roll-off. Crosstalk is specified at -67 dB at 1 MHz — this is the isolation between the off-channel and the on-channel at that frequency. For a 1 MHz analog signal, the bleed from the unused path is roughly 0.05% of the signal amplitude, which is acceptable for 10-bit to 12-bit accuracy in many mixed-signal chains. Switching times are 45 ns max for turn-on (Ton) and 26 ns max for turn-off (Toff), fast enough to handle channel hopping in a 10 MHz sampled system without missing a sample window.
Charge injection and leakage — what they mean for sample-and-hold and high-impedance nodes
Charge injection is 3 pC typical. When the switch opens, this charge dumps onto the output node — in a sample-and-hold front end driving a 10 pF hold capacitor, 3 pC translates to a 300 mV glitch. The downstream ADC's acquisition time must settle this before conversion. Off-channel leakage current (IS(off)) is a maximum of 2 nA. At a 10 MOhm source impedance, this leakage develops 20 mV of offset error — negligible for most applications but a consideration for picoammeter-level circuits. Channel capacitance (CS(off), CD(off)) is 6.5 pF. This capacitance, combined with the source impedance, forms a low-pass filter that limits the bandwidth at the off-channel node — a 50 Ohm source sees a corner frequency above 500 MHz, but a 10 kOhm source drops it to 2.4 MHz.
RoHS3 compliant (ROHS3 Compliant per the lifecycle entry), meaning it meets the EU directive's latest substance restrictions including the four phthalates. Supplied in Tape & Reel (TR) or Cut Tape (CT) packaging — the reel format is standard for automated pick-and-place assembly in volume production.