Signal
Multiplexer (MUX)
Many-to-one signal routing for sensor scanning and channel selection.
What is it?
A multiplexer routes one of N input signals to a single output, controlled by binary select pins. Common configurations: 2:1, 4:1, 8:1, 16:1. Used to scan multiple sensors into a single ADC, route test signals to one observation point, or select one of many sources to feed downstream logic. Analog MUXes pass signals bidirectionally; digital MUXes only forward in one direction.
When do you need it?
- Connecting 4 or 8 sensors to one ADC input (saves the cost of multiple ADCs).
- Test/debug signal selection, pick which internal node goes to a scope probe.
- Audio channel selection (e.g., picking one of N microphone arrays).
- Address-bus expansion for memory or peripheral selection.
How to pick the right one
- Number of channels
- 2:1, 4:1, 8:1, 16:1, match to your scan width. Cascading two 4:1 MUXes into one final 2:1 also works.
- RON / off-isolation
- Same considerations as SPDT, low RON for low-loss, high off-isolation for cross-talk rejection.
- Bandwidth
- Match to your signal frequency. Audio: 100 kHz is plenty. Video / RF: 100 MHz+.
- Select latency
- Time from select-pin change to output settling. Bounds your max scan rate.
- Single-ended or differential
- Differential MUXes route both halves of a differential pair simultaneously, needed for clean low-noise sensors or high-speed differential signals.
What Magnias offers
Magnias switches for signal routing: MUX7227A-N10 (USB 2.0 / eUSB2 2:1 or 1:2 mux, 3 Ω RON, 3.3 GHz bandwidth, UQFN1.4x1.8-10L), MI3204C-T16 (quad SPDT, which works as a 4-bit 2:1 mux, TSSOP-16L) and MI3157A-TW (single SPDT, SOT363). For more channels, cascade 2:1 stages or ask your FAE.
Common questions
MUX bandwidth. What limits it?
Internal switch capacitance and RON. The signal sees RON × COFF as a low-pass filter on each non-selected channel. Cascading MUXes multiplies the effective filter.
Can I use an analog MUX for high-speed digital?
Yes if bandwidth is high enough. But dedicated digital MUXes have better timing specs and lower skew between channels.
How do I extend an 8:1 MUX to handle 16 inputs?
Use two 8:1 MUXes feeding a 2:1 MUX, with the extra select bit driving the 2:1 stage. Each stage adds its own RON and capacitance, so check bandwidth after cascading.