How do I size Rsense for efficiency and resolution?

Choose VCS≈50–100 mV, compute Rsense=VCS/(I·G). Check I²R power and ΔT, and ensure ADC LSB ≤0.5% FS for LEDs/LDs or ≈1% for battery-CC. Prefer four-terminal shunts and include TCR in calibration.

How do I set and clamp LDC k-gain?

Measure harness resistance and set k≈Rline. Inject k·I into Vref or digitally, then clamp k at light load to avoid noise. Re-verify phase margin ≥45–60° and accuracy across cable variants.

How to suppress low-duty spikes and flicker?

Use slope compensation or error-amp slew limits and a short soft-start per PWM pulse; add a peak clamp if needed. Avoid 100–200 Hz bands and verify plateau flatness with fixed-phase sampling. Hybrid dimming helps at very low duty.

Remote-sense RC starting values and validation?

Start with 10–100 Ω and 1–10 nF at the sense input for a pole near 0.1·fsw. Route as tight differential pairs, away from SW. Validate by Bode or load-step ring-down and adjust for margins.

Laser diode safety with APC?

Use an APC outer loop for optical power while CC handles fast dynamics. Limit slew and clamp peaks at enable/disable; validate no ringing and record overshoot, triggers, and thermal rise vs. SOA.

DCR vs. shunt sensing trade-offs?

DCR cuts cost and loss but drifts with temperature/tolerance; needs RC matching and calibration. A four-terminal shunt with a differential amplifier and Kelvin routing delivers better accuracy at the cost of I²R loss.

How to minimize differential and common-mode EMI?

Shrink the high-di/dt loop, keep clean planes under analog, add RC snubbers for SW ringing. For common-mode, avoid planes under SW and filter I/O with CM chokes/Y-caps when permitted. Tune gate-R wisely.

Thermal rules for shunt and power stage?

Estimate I²R power, verify ΔT, use four-terminal shunts and symmetric copper; via-stitch under FETs and inductors. Keep the shunt away from hot parts and account for TCR in calibration.

What should validation include?

Accuracy over temperature and cables, 0↔100% steps, PWM low-duty quality, CC→CV handover, and sense-open/bounce faults. Use the longest harness; log margins, triggers, overshoot, and thermal rise.

CC Buck with Remote Sense for LED, Battery & Laser Loads

Q: How does remote (Kelvin) sensing improve CC accuracy vs. local sensing?

Kelvin pairs measure the drop across the load or shunt without copper path losses, removing I·R wiring error from feedback. Add a small R–C at the sense input and route as a tight differential pair to suppress noise and preserve stability.

Q: When should I choose peak, valley, or average current mode?

Peak mode is simple and fast but needs slope compensation; valley mode is stable at high duty; average current mode regulates mean current with lowest ripple and best linearity for precise LED/LD and battery-CC, at the cost of more involved compensation.

Q: PWM vs. analog vs. hybrid dimming?

Use PWM for wide range; add analog trim for low-level linearity. Keep PWM ≥2 kHz (≥20 kHz for cameras). For LDs, prefer average-current control with soft edges and slew limits to avoid overshoot.

Q: Bode targets for average current mode?

Set crossover near fsw/10…/20 with phase margin ≥45–60° and gain margin ≥6–10 dB. Place a compensator zero at the dominant pole and a HF pole to roll off noise. Include sense-RC and amp BW effects.

Q: How do CC and CV loops share control?

Keep CC faster than CV by ≥3:1. Add clamps and anti-windup, use small hysteresis at the threshold, and optionally reduce CC bandwidth in the handover zone for smooth transitions.

A load-tracking CC buck closes the loop at the load pins (Kelvin sense) so wire/connector drops, LED temperature drift, and battery impedance swings don’t corrupt current. With appropriate tracking/feed-forward, it keeps true constant current under dynamics and mitigates flicker/overcharge risk. For batteries/laser diodes, define a clean CC→CV (or APC) handover boundary to protect the device.

← Back to Buck / Boost / Buck-Boost Regulators

Remote-sense CC buck: Kelvin taps remove wiring/thermal errors; tracking keeps true constant current; define CC→CV/APC boundary for batteries and laser diodes.

Principle & Topologies — Current-Mode Buck and Sensing Choices

A constant-current buck regulates the load current by comparing a sensed current signal to a reference and adjusting duty cycle accordingly. The current-mode type and the sense method determine accuracy, drift, efficiency, and stability—especially when combined with remote (Kelvin) sense.

Peak Current Mode

Fast response; simple inner loop.
Needs slope compensation at high duty to avoid sub-harmonics.
Risk of peak overshoot with LED/LD at very low PWM duty.

Valley Current Mode

Good stability at high duty ratios.
Up-step load transients recover slightly slower than peak mode.

Average Current Mode

Best linearity and lowest ripple; ideal for precise CC (LED, battery-CC, LD/APC).
Compensation more involved; bandwidth limited by dual-loop interaction.

Peak/Valley are single-sampled per cycle; Average closes an inner current loop to regulate the mean value.

Rsense (High/Low Side)

Highest accuracy & linearity; power loss = I²R.
Use Kelvin traces; choose low-TC shunt; check heat rise.

Inductor DCR Sensing

Low cost/loss; requires RC time-constant matching.
Compensate DCR temperature drift; tolerance is higher.

Amplified / Differential Sense

Low drift with small shunt; supports remote Kelvin sense.
Verify CMRR/bandwidth and common-mode range vs. spikes.

Kelvin differential sense with small R_s–C_f at the sense pair, routed as a tight pair to a high-CMRR amplifier; AGND and PGND meet at a clean single point.

Remote Sense Tips

Start with R_s=10–100 Ω, C_f=1–10 nF; set the pole around f_sw/10.
Route the sense pair away from switch nodes; keep it short and tightly coupled.
Reference the amplifier to AGND; tie AGND–PGND at a single star point.

CC Loop Design — Targets, Quantization, and Protection

Set Targets (I_LED, I_BAT, I_LD)

I_TARGET = V_CS / (R_SENSE · G_SENSE). Prefer small V_CS (≤100 mV) and adequate gain for efficiency and resolution. Coordinate CC→CV/APC thresholds for battery and laser safety.

Quantization & Measurement

DAC step to current: ΔI ≈ ΔV_DAC / (R_SENSE·G_SENSE).
ADC estimate: I ≈ V_meas / (R_SENSE·G_MEAS); calibrate shunt TC and amp drift.
Resolution goals: LED/LD ≤0.5% of full-scale; battery-CC ≈1%.

Bandwidth & Stability

Target loop bandwidth ≈ f_sw/10…f_sw/20.
Phase margin ≥ 45–60°; limit error-amp output to avoid wind-up.
When paired with CV/APC outer control, add clamps and anti-windup.

Current Limit & Foldback

Use a hard limit I ≤ I_LIM plus a foldback curve to reduce stress during faults:

I_OUT(V_OUT) = { I_MAX for V_OUT ≥ V1; I_MAX − k·(V1 − V_OUT) for V2 ≤ V_OUT < V1; I_MIN for V_OUT < V2 }

Typical safeguard: I_MIN = 20–40% of I_MAX for auto-recovery.
Set k by thermal limits and SOA of FET/inductor/diode/shunt.

_OUT I_OUT V1 V2 Foldback SOA

Foldback reduces stress inside the SOA; choose V1, V2, and slope k from thermal limits.

Load-Specific Notes

LED: combine PWM + analog dimming; manage low-duty spikes with soft-start/slope control; avoid flicker bands <2 kHz.
Battery (CC phase): define a clean CC→CV threshold; limit input power during pre-charge.
Laser diode: use APC as outer loop; prioritize average-current control and overshoot suppression.

Load-Tracking Strategies — Line Drop Compensation, Temperature & Impedance

Load tracking keeps current accuracy at the load pins under wire/connector drops and device variations. Combine line drop compensation (LDC/LRC), appropriate loop bandwidth, and slope control with remote (Kelvin) sense to suppress overshoot and maintain stability.

Line Drop Compensation (LDC/LRC)

Compensate cable/connector resistance by feeding a portion of the sensed current into the reference: V_ref,eff = V_ref + k·I_sense, where k ≈ R_line.

Analog: small resistor mixer from CS-AMP to the reference node.
Digital: add k·I in firmware; clamp 0 ≤ k ≤ k_max.
Tune with the target harness; verify <0.5% (LED/LD) or 1% (battery-CC) error.

Step Response & Bandwidth

Base current-loop BW ≈ f_sw/10 … f_sw/20.
With LDC feed-forward, BW can rise by ~20–30% if phase margin ≥45°.
Use slope compensation / error-amp slew limiting to curb peak spikes.

Temperature & Impedance Tracking

LED: Vf(T) ≈ −2 mV/°C per LED; add small I(T) correction or LUT.
LD: threshold rises with T; limit slew and clamp current under APC control.
Battery: R_bat(SoC,T) varies; narrow loop BW near CC→CV boundary.

Feed a fraction of the sensed current into the reference to cancel line drops. Calibrate k with the target harness; clamp at light load.

LDC allows a modest bandwidth increase if phase margin stays safe. Use slope compensation or slew limiting to avoid low-duty peak spikes.

Recommended Starting Points

Item	Start Value	Notes
LDC gain k	≈ cable R (measured)	Clamp 0…k_max; reduce at light load.
Sense RC (R_s,C_f)	10–100 Ω · 1–10 nF	Pole ≈ 0.1·f_sw.
Loop BW	f_sw/10…/20	+20–30% with LDC if PM ≥45°.
Slope / slew limit	enable at low duty	Suppress sub-harmonics and spikes.

Practical Tips

Measure harness resistance hot and cold to bound k.
Schedule current sampling at a fixed phase within each cycle.
Check stability with the longest cable and worst connector pair.

Special Scenarios — LED Dimming, Battery CC→CV, and Laser APC

LED — PWM/Analog Dimming & Flicker Control

Use hybrid dimming: PWM for mid/high levels, analog trim for low levels.
Set PWM above 2 kHz (≥20 kHz for camera use); avoid 100–200 Hz flicker bands.
Mitigate low-duty spikes: soft-start, slope comp, peak clamp, or preheat stair.
Apply gamma/LUT to achieve perceived linear brightness.

Battery — Pre-charge, CC Segment, CC→CV Handover

Define tight CV threshold (±1%); reduce current-loop BW near CC→CV boundary.
Pre-charge: I_pre ≈ 0.05–0.1C (example) with input power limiting.
Enable foldback and thermal protection; verify worst-case short/ESD events.
Optimize ESR zero in CV stage to limit ripple for battery longevity.

Laser — APC (Constant Luminous Power) & Overshoot Suppression

Use APC as an outer loop (photodiode → power target); keep CC as the fast inner loop.
Limit slew and clamp current; prevent overshoot/undershoot during on/off.
Route PD and sense as tight differential pairs; prioritize high CMRR.

LED uses hybrid dimming with spike control; Battery narrows loop BW near the CC→CV boundary; Laser relies on APC with inner CC and clamps.

Starting Ranges

PWM frequency: ≥2 kHz (≥20 kHz for cameras).
Pre-charge current: 0.05–0.1C (example; verify vendor limits).
APC bandwidth: < current-loop bandwidth (outer loop slower).

Remote Sense & Layout — Kelvin, Grounds, High di/dt Loops

Accurate constant current requires Kelvin (remote) sensing, a clean AGND/PGND reference, and the smallest possible high-di/dt loop. This section gives PCB rules you can copy directly.

Kelvin Connections

Sense as a tight differential pair, away from the SW node.
Add small Rs–Cf at the sense input (start: 10–100 Ω & 1–10 nF).
Take Kelvin points at the load pads or connector pins, not the power copper.

AGND / PGND Partition

CS-AMP and error amp reference AGND; power devices return to PGND.
Join AGND–PGND at a single star point or short bridge in a quiet area.
Keep a continuous ground plane under analog traces; avoid SW copper above it.

Shunt (RSENSE) Thermals

Power loss P = I²R; prefer 4-terminal metal shunts (1206/2512 or dedicated).
Use symmetrical copper to avoid gradients that skew reading.
Include R(T) in calibration; separate from hot FET/diode areas.

Kelvin differential sense with small R–C at the input; analog ground (AGND) and power ground (PGND) meet at a quiet single point.

Use a 4-terminal shunt and symmetric copper to minimize thermal gradients; include R(T) in calibration for accurate current.

Keep the switch loop tiny and local; route returns directly beneath or with paired vias to close the loop area.

Layout Tips

Do not run sense lines under or near the SW copper; cross at 90° if unavoidable.
Place the shunt away from hot FETs/diodes; give airflow or copper to spread heat.
Maintain a continuous plane under analog circuits; cutouts increase loop area and noise.

EMI & Thermal — Differential/Common-Mode Control and Heat Paths

Control EMI at the source, along the coupling path, and at the receiver. Balance copper for low loss without enlarging radiating areas, and design clear thermal paths for the inductor, FETs, and shunt.

Radiation & Common-Mode

Minimize switch-loop area; damp with small series R or RC where needed.
Avoid sensitive planes beneath SW copper; use CM chokes/Y-caps on I/O if allowed.
Gate loop: keep tight; set gate resistor to tame ringing and dV/dt.

Conducted Emissions

Input π/LC with clean ground partition at the filter.
Set ESR zero on the output to stabilize the loop; add snubber to tame SW spikes.
Verify with LISN: compare peak vs. average limits near harmonics.

Thermal Paths

Inductor: consider copper + core losses; allow airflow and via-stitch to inner planes.
Sync FET: spread heat with multiple vias to ground/heatsink; check SOA at faults.
RSENSE: keep symmetrical copper; avoid hot spots; include TCR in calibration.

Reduce differential-mode loop area, contain common-mode on I/O with chokes/Y-caps when permitted, and plan thermal paths for SW node, FETs, and the inductor.

EMI & Thermal Quick Ranges

Gate resistor: start 2–10 Ω; increase until ringing is controlled with acceptable loss.
Snubber: choose R,C to target SW peak; verify thermal impact.
Via stitching: ≥4–8 vias near FET tabs and inductor pads to inner planes/heatsink.

Stability & Compensation — Small-Signal Model, Bode Targets, Dual-Loop Handover

Design the constant-current loop for a clean phase margin (≥45–60°) and gain margin (≥6–10 dB), with crossover typically around f_sw/10…/20. If a CV outer loop is enabled, keep bandwidth separation and add clamps/anti-windup to avoid control contention at the CC→CV boundary.

Small-Signal Model

Power stage ≈ single pole + ESR zero; current sampling adds extra pole/phase loss.
Average current mode: inner current loop + outer reference control.
Account for sense RC and amplifier bandwidth in phase budget.

Compensation Flow

Pick f_c ≈ f_sw/10…/20; place Type-II zero near plant pole.
Use HF pole to roll off noise; verify with longest cable and sense RC.
With line-drop feed-forward, re-check phase margin >=45°.

Dual Loop (CC→CV)

Bandwidth ratio CC:CV ≥ 3:1; add clamps & anti-windup on error amp.
Define clean CC→CV hysteresis; fix sampling phase near the boundary.
Optionally slow the fast loop slightly in the handover zone.

Set crossover around fsw/10…/20; ensure ≥45–60° phase margin after accounting for sense RC and amplifier bandwidth.

Place the compensator zero to cancel the dominant plant pole; set a HF pole to reduce noise and keep the desired crossover.

Keep CC as the fast inner loop and CV slower; add clamps and an anti-windup path to prevent integrator wind-up at the CC→CV boundary.

Stability Tips

Measure with the longest cable and target harness; sense RC lowers phase—budget for it.
Fix sampling phase per cycle; average or window to reduce jitter near crossover.
Record final margins and f_c in the validation matrix for reproducibility.

Validation & Test — CC Accuracy, Transients, PWM Quality, Remote-Sense Faults

CC Accuracy (Temp/Line)

Temperature sweep −20…+85 °C; log I/V/T, shunt TC, and amp drift.
Line sweep: short/mid/long harness, different connectors.
Targets: LED/LD ≤±0.5%FS; Battery-CC ≤±1%FS.

Load Step & PWM Dimming

0↔100% steps: overshoot/undershoot ≤±5%; settling in hundreds of μs.
PWM: low-duty spikes, plateau flatness, symmetry, flicker ≥2 kHz (≥20 kHz for cameras).
Schedule sampling at a fixed phase within each cycle.

Remote Sense Faults

Open on either Kelvin line → safe fallback (limit/disable/alert).
Connector bounce & hot-plug: no harmful spikes or heating.
Worst case: short/open, thermal, UV/OV, surge → log SOA compliance.

Hold accuracy within the target band across temperature and harness variants; calibrate shunt TC and line-drop compensation.

Validate overshoot/undershoot and settling on full steps; at low PWM duty, control opening spikes and ensure flat plateaus.

Validation Matrix

Test ID	Condition	Setup	Criteria
ACC-T	Temp sweep −20…+85 °C	Chamber; shunt TC logged	LED/LD ≤±0.5%FS; Battery-CC ≤±1%FS
ACC-L	Cable/connector variants	Short/Mid/Long harness	Within target band
STEP	0↔100% load step	Scope @ fixed phase	Overshoot/undershoot ≤±5%; settle < 500 μs
PWM	Low-duty PWM	≥2 kHz (≥20 kHz camera)	Spikes clamped; plateau flat
RS-FLT	Remote sense open/bounce	Simulate connector faults	Safe fallback ≤2 ms; no harmful heat

Results Log

Setpoint	Measured	Error	Temp	Cable	Notes

Validation Tips

Capture Bode plots at final harness; store f_c, PM, GM in the matrix.
Log thermal rise for shunt, FETs, and inductor during faults and steps.
Use worst-case cable and connector pair for the acceptance run.

IC Selection — 7-Brand Families & How to Filter

Start with I_MAX, V_IN, and load voltage window (V_LED/V_LD/V_BAT), then decide dimming and sense method (high-/low-side shunt, DCR, differential). Calibrate temperature drift and ensure AEC-Q100 / automotive requirements where needed. Below lists families/directions only; part numbers will follow after official-source verification.

Key Filters

I_MAX (peak/continuous), LED/LD surge margin, battery CC limit.
V_IN range (e.g., 6–18 V automotive, 12/24/48 V industrial).
V_LED/V_LD/V_BAT window; series LED count / battery cells.
Dimming: PWM, analog, or hybrid; low-duty linearity & flicker.

Sensing & Accuracy

High-/low-side shunt, inductor DCR, differential amplifier.
Remote (Kelvin) sense support; amplifier BW & CMRR.
Reference drift, shunt TCR, ADC/DAC resolution mapping.

Compliance & Control

AEC-Q100 / automotive features, diagnostics.
Peak/valley/average current mode options.
CC→CV handover and fault handling ecosystem.

Filter by current/voltage first, then dimming and sensing; finalize with Kelvin accuracy and AEC-Q100 requirements.

Texas Instruments (TI)

LED / constant-current buck driver families.
Controller series for peak/valley/average modes.
Direction examples: LM3409-class, TPS92xxx-class.

STMicroelectronics (ST)

LED buck drivers: LED2001/LED6001 direction.
Constant-current buck controllers (incl. auto variants).
Good app notes on EMI and dimming.

onsemi

NCP/NCL LED buck controller directions.
NCV automotive families for lighting.
Rich EMI/design collateral.

Renesas

Constant-current / LED buck controllers.
Automotive series; multi-channel options.
Average current-mode choices available.

NXP

Automotive lighting drivers: ASL/AFE directions.
Diagnostics, fault reporting, dimming features.
Good for headlamps/taillamps, multi-string.

Microchip

MCP16xx-class controllers + LED drivers.
Industrial/auto variants and reference designs.
Flexible sensing and PWM dimming support.

Melexis

Automotive LED drivers: MLX10xxx/MLX81xxx directions.
Lighting diagnostics, LIN/CAN options in families.
Targeted for exterior lighting and clusters.

Note

This section lists families/directions only. In the next step we will publish procurement-ready PNs with key parameters and links to official datasheets for each of the seven brands.

Design Cheatsheets — Fast Formulas & Rules of Thumb

Quick calculators for R_SENSE, shunt power, line drop compensation, dimming linearity, and loop bandwidth. Use these as starting points and refine with measurement and thermal checks.

Quick Formulas

I_TARGET = V_CS / (R_SENSE·G_SENSE)
R_SENSE = V_CS / (I_TARGET·G_SENSE)
P_SENSE = I²·R_SENSE → size package & copper symmetrically
V_ref,eff = V_ref + k·I, with k ≈ R_line
I = I_max·D^γ (gamma dimming, γ≈1.8–2.4)
f_c ≈ f_sw/10…/20; PM ≥45–60°

Rules of Thumb

Sense RC: 10–100 Ω & 1–10 nF; pole ≈ 0.1·f_sw.
Gate-R: 2–10 Ω start; tune for ringing vs. loss.
LDC clamp: reduce k at light load; hot/cold harness calibration.
PWM: ≥2 kHz (≥20 kHz for cameras); hybrid dimming at low duty.
AEC-Q100: check surge/load-dump, diagnostics, fault flags.
Thermal: 4-terminal shunt + symmetric copper; via-stitch FET/inductor.

Keep these at hand when drafting the current stage; refine with measurement and thermal constraints.

Starter Values (Edit to Suit Your Design)

Item	Default	Range / Note
V_CS	50–100 mV	Lower loss vs. resolution trade
Sense RC	10–100 Ω · 1–10 nF	Pole ≈ 0.1·f_sw
Gate-R	2–10 Ω	Tune ringing vs. switching loss
PWM freq	≥2 kHz	≥20 kHz for camera use
BW target	f_sw/10…/20	Check phase margin ≥45–60°

Next Step

Confirm the target ranges and families. I will then deliver a 7-brand PN table cross-checked with official datasheets (I_MAX, V_IN, sense, dimming, accuracy, AEC) for procurement.

AQs — CC / Load-Tracking Buck FAQs

Practical answers for constant-current buck regulators with remote (Kelvin) sense, line-drop compensation, and load tracking across LEDs, batteries, and laser diodes.

Key reminders before you dive into the questions.

How does remote (Kelvin) sensing improve CC accuracy vs. local sensing?

Kelvin pairs measure the drop across the load or shunt without the voltage error from copper paths and connectors. That eliminates I·R wiring losses from the feedback loop, keeping current setpoint tight across cable length and temperature. Add a small R–C at the sense input and route as a tight differential pair.

When should I choose peak, valley, or average current mode?

Peak mode offers simple hardware and fast up-steps but needs slope compensation at high duty. Valley mode behaves well at high duty and softens sub-harmonics. Average current mode regulates the mean current with lowest ripple and best linearity—ideal for precise LED/LD and battery-CC—but requires more careful compensation.

How do I size R_SENSE for both efficiency and ADC resolution?

Start with V_CS=50–100 mV to limit dissipation, then compute R_SENSE=V_CS/(I·G_SENSE). Check I²R power and temperature rise, and ensure ADC LSB maps to ≤0.5% FS (LED/LD) or ≈1% (battery-CC). Prefer four-terminal shunts and include TCR in calibration over −20…+85 °C.

Line Drop Compensation: how do I estimate the k-gain and avoid instability?

Measure harness resistance hot/cold and set k≈R_line. Inject k·I either via a resistor mixer into Vref or digitally. Clamp k at light load to avoid noise amplification. After enabling LDC, re-check phase margin (≥45–60°) and confirm current accuracy across cable variants and connectors.

PWM vs. analog vs. hybrid dimming for LEDs and LDs?

Use PWM for wide dynamic range and color stability; add a small analog trim for low-level linearity (“hybrid”). Keep PWM ≥2 kHz to mitigate flicker (≥20 kHz for cameras). For LDs, favor average-current regulation and soft edges; limit slew to suppress overshoot and ringing near turn-on/off.

How do I suppress low-duty spikes and visible flicker?

Combine slope compensation or error-amp slew limiting with a short soft-start on each PWM pulse. Add a peak clamp if needed. Keep the PWM frequency out of 100–200 Hz bands and verify plateau flatness with fixed-phase sampling. Hybrid dimming helps preserve linear steps at extremely low duty cycles.

What are practical Bode targets for average current mode?

Set crossover around f_sw/10…/20 with phase margin ≥45–60° and gain margin ≥6–10 dB. Place a compensator zero near the plant pole and a high-frequency pole to roll off noise. Include sense-RC and amplifier bandwidth in the phase budget; re-verify with the longest cable installed.

Remote-sense RC: where do I start and how do I validate it?

Begin with R=10–100 Ω, C=1–10 nF at the sense pins; target a pole near 0.1·f_sw. Route the pair tightly, away from the SW node, and reference to AGND. Validate stability via Bode or load-step ring-down; adjust RC if phase loss compromises margins or noise leaks into the ADC.

How do CC and CV loops share control in a charger?

Keep CC as the fast inner loop and CV slower by ≥3:1 bandwidth. Add clamps and an anti-windup path around the integrator to avoid saturation at the CC→CV boundary. Use a small hysteresis on the CV threshold and optionally reduce current-loop bandwidth within the handover window for smooth transitions.

Laser diode safety: where does APC fit and what to clamp?

Use an optical APC outer loop to regulate power while the CC buck handles fast current dynamics. Limit slew, clamp peaks on enable/disable, and verify no ringing with the real cable and photodiode wiring. Record maximum overshoot, trigger times, and thermal rise inside a worst-case SOA matrix.

Inductor DCR vs. shunt sensing: accuracy and drift trade-offs?

DCR saves cost and loss but suffers tolerance and temperature drift, requiring RC matching and calibration. A metal shunt offers superior linearity and predictable TCR; with a differential amplifier and Kelvin routing, it yields the most stable current—at the price of I²R dissipation and board area.

How do I minimize differential and common-mode EMI in a CC buck?

Shrink the high-di/dt switch loop, keep a continuous ground under analog traces, and add RC snubbers where SW ringing occurs. For common-mode, avoid planes under SW copper; filter I/O with CM chokes and Y-caps when permitted. Tune gate resistance to balance ringing suppression and switching losses.

Thermals on the shunt and power stage: quick rules?

Estimate P_SENSE=I²R and verify ΔT for the chosen package; use four-terminal shunts and symmetric copper to avoid gradients. Provide via-stitching under MOSFET tabs and inductor pads. Keep the shunt away from hot components and include TCR in current calibration across the full operating range.

What should a validation plan include before release?

Cover CC accuracy over temperature and cables, 0↔100% load steps, PWM low-duty quality, CC→CV handover, and remote-sense faults (open/bounce). Use the longest harness and worst connectors. Log phase/gain margins, protection trigger times, peak overshoot, and thermal rise against the SOA envelope.

Submit Your BOM — 48-Hour Cross-Brand Review

We verify current limits, voltage windows, sensing topology, dimming plan, EMI/thermal paths, and propose procurement-ready options across seven brands.

Submit Your BOM Typical return: shortlist + risks + starter parameters