551 Leaky Integrate and Fire Neuron
551 : Leaky Integrate and Fire Neuron
- Author: Chris Htet
- Description: Fixed-point accumulator with leak and a comparator to fire a spike when voltage is greater than threshold
- GitHub repository
- Open in 3D viewer
- Clock: 50000000 Hz
How it works
A leaky-integrate-and-fire (LIF) neuron implemented in 8-bit signed Q4.4 fixed-point. It’s designed to be tapeout-friendly (adds/subs/shifts only, no multiplies) with saturating arithmetic and a refractory period.
Per clock (when en=1), it
- Integrates input current into a membrane potential V.
- Applies leak (exponential decay toward 0 via arithmetic right-shift).
- Checks threshold on the next potential (V_next) and emits a a spike signal and set V to Max if crossed.
- Resets and holds during a programmable refractory window so it won’t spike again immediately.
How to test
Using input CLk, Reset, and Current
External hardware
ADALM2000
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | I_q4_4[0] (LSB) | spike (1-cycle pulse) | |
| 1 | I_q4_4[1] | refractory (active-high) | |
| 2 | I_q4_4[2] | V_dbg[0] = V[4] (Q4.4) | |
| 3 | I_q4_4[3] | V_dbg[1] = V[5] (Q4.4) | |
| 4 | I_q4_4[4] | V_dbg[2] = V[6] (Q4.4) | |
| 5 | I_q4_4[5] | V_dbg[3] = V[7] (MSB, Q4.4) | |
| 6 | I_q4_4[6] | ||
| 7 | I_q4_4[7] (MSB) |