What this SPST-NC switch brings to the signal path
The Maxim Integrated MAX317ESA+ is a single-pole single-throw normally-closed (SPST-NC) analog switch in an 8-SOIC package. It routes one analog or digital signal through a 35 Ohm max on-resistance channel, with switching times of 175 ns (turn-on) and 145 ns (turn-off). The -85 dB crosstalk at 1 MHz keeps channel isolation clean in multiplexed audio or precision measurement chains. It operates from a single supply of 10 V to 30 V or dual supplies of ±4.5 V to ±20 V, covering common industrial and test-equipment rails.
The 35 Ohm max on-resistance sets the insertion loss and voltage drop across the switch. For a 1 V signal into a 10 kΩ load, the loss is under 0.35% — negligible for most analog paths. The 3 pC charge injection matters when the switch drives a high-impedance sample-and-hold or integrator; a 10 pF hold capacitor sees a 300 µV glitch, which may need settling time in a 12-bit system. Channel-to-channel matching of 2 Ohm max ensures consistent attenuation when multiple switches are used in parallel or in a gain-setting network.
Leakage and capacitance — guarding the off-state
Off-state leakage is 250 pA max, and channel capacitance is 8 pF on both source and drain pins. At 1 MHz, the 8 pF capacitance presents about 20 kΩ of reactive impedance — fine for low-frequency analog, but worth budgeting in RF or high-speed digital multiplexing where the off-channel can couple signal through the parasitic path.
The 8-SOIC package is surface-mount, compatible with standard reflow profiles. ROHS3 compliant, no exemptions for lead or cadmium.