EMC2101 — i2c address & wiring
SMBus/i2c fan controller: PWM drive, RPM readback and dual temperature channels.
Key facts
EMC2101 at a glance
| i2c address | 0x4C fixed address |
|---|---|
| Logic voltage | 3–3.6 V |
| Type | driver |
| Part | Microchip EMC2101 |
| Ships with | generic modules — plain 0.1″ headers, no connector system |
| Datasheet | Microchip EMC2101 — manufacturer documentation ↗ |
The chip
What the Microchip EMC2101 actually is
Fan controller with a 4-pin PWM (or DAC/linear) drive output, a tachometer input for true RPM readback, an internal temperature sensor plus an external-diode channel you can point at a CPU or hot MOSFET, and an optional hardware lookup table that maps temperature to fan speed on its own — set the curve once and it manages the fan with no host traffic at all.
Watch out: It's an SMBus part at heart: a bus timeout can drop transactions if the host stalls mid-transfer. Its fixed 0x4C is also the classic remote-temp-sensor address (LM90/MAX6654 family), so scan before adding one to a board that already monitors temperature.
Wiring
How to connect the EMC2101
The EMC2101 talks i2c at address 0x4C. It runs at 3–3.6 V, so match your host's logic level — if your host is 5 V and a board on the bus is 3.3 V-only, add a level shifter. Use the compatibility checker to confirm the exact cable for your setup.
The address is fixed, so two EMC2101s can't share a bus directly — the address-conflict guide covers the workarounds (multiplexer, second bus).
Wiring is the usual four: power, ground, SDA and SCL, plus pull-up resistors — almost always already fitted on the breakout. Nothing showing up? Run an i2c scan first; if the bus is silent, the 7-step checklist finds it faster than guessing.
Alternatives
Other i2c drivers
Watch the bus
Boards that clash with the EMC2101
These want an address the EMC2101 also answers (0x4C), so they can't share a bus with it untouched. If one is address-selectable, strap it elsewhere; if not, the conflict guide covers the multiplexer and second-bus routes, and the collision roundup explains why a scan won't warn you.
Get one
Questions
EMC2101 i2c FAQ
What is the EMC2101's i2c address?
The EMC2101 sits at a fixed address of 0x4C. It can't be changed, so two of them can't share one bus without a multiplexer or a second bus.
What voltage does the EMC2101 run at?
The bare chip runs 3.0–3.6 V, but fan-controller modules like this one are built for 3.3–5 V hosts — check your specific board. The fan itself runs from its own 5 V or 12 V rail, never the logic supply.
Can I use two EMC2101s on one i2c bus?
Not directly — every EMC2101 answers to 0x4C, so two on one bus would collide. Use a TCA9548A multiplexer to give each its own channel, or put the second one on a separate bus.
Does the EMC2101 come as a plug-together breakout?
Not in the mainstream connector ecosystems — EMC2101 modules are generic boards with 0.1″ headers, so you'll be soldering headers and running jumper wires to SDA, SCL, power and ground.
What should I watch out for with the EMC2101?
It's an SMBus part at heart: a bus timeout can drop transactions if the host stalls mid-transfer. Its fixed 0x4C is also the classic remote-temp-sensor address (LM90/MAX6654 family), so scan before adding one to a board that already monitors temperature.