SN3257-Q1 Automotive 2:1 (SPDT) 4-Channel Switch with 1.8 V Logic

Texas Instruments' SN3257-Q1 automotive-grade complementary metal-oxide-semiconductor (CMOS) switch supports high-speed signals with low propagation delay. This device offers a 2:1 (SPDT) switch configuration with four channels, making it ideal for multi-lane protocols such as SPI and I²S. The switch supports bidirectional analog and digital signals on the source (SxA, SxB) and drain (Dx) pins and can pass signals above the supply up to V_DD x 2, with a maximum input and output voltage of 5.5 V.

The SN3257-Q1 has an active-low EN pin that is used to enable and disable all channels simultaneously. When the EN pin is LOW, one of the two switch paths is selected based on the state of SEL pin. Powered-off protection up to 3.6 V on the signal path of the SN3257-Q1 provides isolation when the supply voltage is removed (V_DD = 0 V). Without this protection feature, switches can back-power the supply rail through an internal ESD diode and cause potential damage to the system.

Fail-safe logic circuitry allows voltages on the logic control pins to be applied before the supply pin, protecting the device from potential damage. The logic control inputs have 1.8 V logic compatible thresholds, ensuring TTL and CMOS logic compatibility. An integrated pull-down resistor on the logic pins removes external components which reduces system size and cost.