Low on-resistance, normally-closed signal switch
The MAX4646EUK+T is a single-pole single-throw (SPST) analog switch from Analog Devices, configured normally-closed (NC). Its headline spec is a maximum on-resistance of 2.5 Ohm — low enough to pass a precision analog signal with minimal attenuation and voltage drop across the switch, which matters when the downstream ADC reference or load impedance is in the low kilo-ohm range.
Switching speed and signal integrity parametrics
Turn-on time is 15 ns max, turn-off 10 ns max — these set the throughput ceiling in a multiplexed data-acquisition front-end or an audio routing matrix. The charge injection is rated 5 pC typical, a figure that determines how much glitch energy couples onto the signal path each time the switch toggles; in a sample-and-hold circuit this translates directly into hold-step error. Off-state leakage is 250 pA max at 25°C, and the off-capacitance on both source and drain pins is 17 pF each. The leakage floor matters when the switch isolates a high-impedance sensor node — 250 pA into a 10 MOhm source creates a 2.5 mV offset error, a factor in precision DC paths. The 17 pF off-capacitance, combined with the off-state resistance, sets the isolation bandwidth; above roughly 10 MHz the capacitive feedthrough dominates the off-isolation. Channel-to-channel matching (ΔRon) is 100 mOhm max — a single-channel part, but the matching spec tells you the on-resistance repeatability from unit to unit within a reel, relevant if multiple parts are used in a gain-setting or divider network where ratiometric accuracy depends on matched switch resistance.
Housed in a 5-pin SOT-23 (SC-74A) package, the supplier device package is SOT-23-5. The footprint is shared across hundreds of analog switches and op-amps — a standard 0.95 mm pitch, 2.9 mm body length.
It is RoHS3 compliant (2011/65/EU + 2015/863), with no exemptions.