Single SPDT switch with dual-supply flexibility
The MAX319ESA+ is a single-pole double-throw (SPDT) analog switch from Analog Devices, configured as a 2:1 multiplexer/demultiplexer. It switches one common terminal to either of two independent I/O pins, with a break-before-make timing that prevents momentary shorting between channels. Rated for single-supply operation from 10 V to 30 V, or dual supplies from ±4.5 V to ±20 V, this part can pass bipolar signals without a DC bias — a common requirement for audio crosspoints and instrumentation front-ends that must handle both positive and negative swings.
On-resistance and channel matching
Maximum on-resistance is 35 Ohm, with channel-to-channel matching held to 2 Ohm max. In a multiplexed data-acquisition system, the matching figure determines the gain error when the load impedance is comparable to the switch resistance — for a 10 kOhm load, 2 Ohm mismatch contributes 0.02 % gain error, negligible for 12-bit systems but relevant at 16 bits. Off-channel leakage is just 250 pA max, and off-capacitance is 8 pF on both source and drain sides. In a high-impedance sensor multiplexer (e.g., a photodiode array with 10 MOhm bias resistors), the leakage current contributes a 2.5 mV offset — manageable with a differential front-end.
Switching speed and charge injection
Turn-on time is 175 ns max, turn-off 145 ns max. This is fast enough for audio-band multiplexing (up to ~1 MHz switching rate) and low-speed data acquisition, but not for video or RF routing where sub-10 ns switching is needed. Charge injection is 3 pC typical. In a sample-and-hold circuit, this charge transfers to the hold capacitor when the switch opens, creating a voltage error. For a 10 nF hold cap, 3 pC produces 0.3 mV of pedestal error — acceptable for 12-bit systems but a consideration for precision applications.
Crosstalk and isolation
Crosstalk between channels is -85 dB at 1 MHz. This means a 1 V signal on the active channel couples only 56 µV into the off channel — sufficient for audio mixing consoles and multi-channel data acquisition where channel bleed must stay below the noise floor of a 16-bit ADC.
Package, temperature, and compliance
Housed in an 8-pin SOIC narrow-body package (0.154-inch width, 3.90 mm), surface-mount only. Ships in a tube — not tape-and-reel, so pick-and-place lines need a tube feeder or a vibratory bowl.