4-Channel RGBW LED PWM Driver

What it is

A synthesizable soft-IP that drives a 4-color (red/green/blue/white) LED by pulse-width modulation: four independent PWM channels share a timebase (prescaler + period) and each has its own duty cycle, so software sets per-channel brightness to mix any color or — for a dashboard telltale — command it cleanly on or off.

Key Features

• 4 independent PWM channels (R/G/B/W) sharing one prescaler + period, each with its own duty, per-channel enable, and a global invert for common-anode/common-cathode wiring
• Config-register even parity on CTRL/PRESC/PERIOD/DUTY_* re-checked every cycle → err_code 1 on any single-bit corruption
• Independent-DMR prescaler and PWM-counter shadows plus a fully diverse recompute of the per-channel compare + gate + invert output path → err_code 9 on any digital stuck-at, up to the output pin
• Deterministic, glitch-free timing: PWM frequency = clk / ((PRESC+1)·PERIOD), duty ratio = DUTY[c]/PERIOD, up to 16-bit (65536-level) resolution
• Disabling (CTRL.EN=0) parks both counters and forces every channel to its defined idle level — no undefined output state
• APB4 slave, 8-register map, zero external IP dependency beyond the shared safety_monitor — drop-in for an existing APB fabric
• Explicit telltale-integration guidance: internal DMR covers the drive logic only, so stuck-on/stuck-off detection past the pin requires an external read-back/bulb-check, documented rather than silently assumed

Standards & Compliance

AMBA APB4 (ARM IHI 0024); ISO 26262 ASIL-B SEooC (SPFM 92.75%, LFM 90.00%, PMHF 2.58×10⁻⁹/h)

Functional Safety

ASIL-B (SEooC) · SPFM 92.75% · LFM 90.00% · PASS

ISO 26262:2018 · FMEDA available · Safety Manual included

Register Map

Getting Started

// Minimal instantiation
led_pwm #(
 .ADDR_W(6)
) u_led_pwm (
 .clk (clk),
 .rst_n (rst_n),
 // APB4
 .p_paddr (paddr),
 .p_psel (psel),
 .p_penable (penable),
 .p_pwrite (pwrite),
 .p_pwdata (pwdata),
 .p_prdata (prdata),
 .p_pready (pready),
 // Safety
 .err_clear (1'b0),
 .err_valid (err_valid),
 .err_code (err_code)
);

Configure via the CTRL register after reset to enable the IP and set operating parameters. Monitor err_valid / err_code for any safety faults reported by the built-in safety monitor.