Monolithic boost regulator ICs integrate the power switch, oscillator, control loop, and protection circuits into a single chip. This reduces external BOM count, saves PCB area, and improves reliability while enabling high-efficiency DC-DC step-up conversion with PFM/PWM mode transitions, UVLO, and thermal safeguards.
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Definition & Fundamentals
Definition. A monolithic boost regulator IC is a DC-DC step-up converter that integrates the power MOSFET, gate driver, control loop, frequency programming, and protections (UVLO/OVP/TSD) in a single package to raise Vin to a higher Vout.
- Integrated switch FET and protections reduce BOM and board area.
- Short loops help EMI; PFM at light load improves efficiency.
- Programmable fSW enables size vs EMI trade-offs.
- Built-in current limit, thermal shutdown, and UVLO/OVP.
- External MOSFETs scale output power and thermal headroom.
- Greater flexibility, but more demanding layout and EMI control.
- More design effort for protections and compensation networks.
- Compact footprint; fewer external parts.
- Predictable EMI with shorter loops and optional spread spectrum.
- Light-load efficiency via PFM or pulse skipping.
- Output current and thermal limits set by internal FET and package.
- Lower flexibility for extreme Vin/Vout ranges vs controller solutions.
Quick math.
Ideal step-up ratio: Vout ≈ Vin / (1 − D). Inductor ripple: ΔIL ≈ (Vin·D) / (L·fSW). Use these to estimate peak current and choose L and fSW.
- Medium power, compact PCB, fast time-to-market.
- Battery-powered systems need light-load efficiency.
- Integrated protections simplify qualifications.
- High current or harsh thermal environment exceeds package limits.
- Very wide Vin/Vout or special switching elements are required.
Architecture Overview
Power and control paths of a monolithic boost regulator IC with integrated switch FET, PWM/PFM logic, error amplifier with compensation, frequency programming, and UVLO/OVP/TSD blocks.
- Power path: Vin → inductor → internal switch FET → rectifier → Cout → Vout.
- Control path: Vout → FB network → error amp with compensation → PWM/PFM logic → gate driver.
- Frequency programming: resistor-set fSW; optional spread spectrum to reduce EMI peaks.
- PFM at light load: pulse-skipping for efficiency; returns to PWM as load increases.
- Protections: UVLO, OVP, current limit, and thermal shutdown safeguard startup and faults.
| Aspect | Monolithic Boost Regulator IC | Boost Controller (External FET) |
|---|---|---|
| Integration | Internal FET, driver, protections built-in | External MOSFET, protections often external |
| EMI/Layout | Short loops; spread-spectrum options | Longer loops; higher layout sensitivity |
| Power/Thermal | Limited by package and internal FET | Scalable with external FETs and cooling |
| BOM/Size | Lower BOM and compact PCB | More parts; larger but flexible |
Operating Principle
This section explains how a boost converter works from an inductor charge–discharge view, then shows the PFM ↔ PWM transition behavior and how UVLO/OVP/thermal events are handled.
Inductor charge & discharge (On/Off stages)
When the internal switch is ON, the inductor stores energy (approximately VL=Vin). When it turns OFF, the inductor current flows through the rectifier to Cout and the load (VL≈Vin−Vout). Ideally, Vout≈Vin/(1−D), where D is the duty cycle.
PWM control
The error amplifier and compensation set the duty cycle D to maintain the target Vout. With higher fSW, ripple and magnetics size reduce, while switching loss may increase.
PFM ↔ PWM transition
At light load the controller enters PFM (pulse-skipping) to cut switching loss; when load rises or ripple/thresholds are met it returns to PWM. Proper thresholds avoid audible noise or low-frequency beat.
Protection event flows (UVLO / OVP / Thermal)
Each protection follows a three-stage pattern: trigger threshold → action (gate stop/limit) → recovery (hysteresis/time). This ensures safe startup and fault handling.
Key Features & Functional Advantages
Adjustable switching frequency (fSW) — EMI / efficiency trade-offs
Higher fSW shrinks magnetics and Cout but raises switching loss and high-frequency EMI peaks. Lower fSW eases efficiency yet increases size. Spread-spectrum can flatten peaks to help pre-scan compliance.
PFM at light load — extends battery life
In PFM, the IC skips pulses to lower switching and driver losses, improving standby/runtime. If audible noise or low-frequency ripple is a concern, lock to forced-PWM or increase minimum load, and review output capacitor ESR and compensation.
Integrated protections & functional safety
Built-in UVLO/OVP/TSD/ILIM provide consistent behavior across lots and temperatures, simplifying validation. For automotive programs, prefer AEC-Q100 variants and align diagnostics with system-level safety goals (ASIL processes). Add input TVS, thermal paths, and Power-Good chaining at the board level.
Select fSW by magnetics/size, then apply spread-spectrum to smooth peaks before compliance testing.
If low-frequency ripple or audible noise appears, force PWM or increase minimum load and review ESR.
Set UVLO above system brown-out; keep OVP headroom for transients; verify TSD hysteresis.
Design Guidelines
Practical rules for inductor/diode/capacitor selection, UVLO setup, suppression of output ringing & overshoot, and loop compensation in a monolithic boost regulator IC.
Inductor selection
- L targets ΔIL ≈ 20–40% of ILavg.
- Isat ≥ Ipeak; low DCR; shielded core.
- ΔIL ≈ (Vin·D)/(L·fSW), Ipeak ≈ Iout·(Vout/Vin)/η + ΔIL/2
Rectifier / diode
- Schottky (low Vf); check leakage at high T.
- Iavg ≥ Iout·(Vout/Vin); Vr ≥ Vout + margin.
- Synchronous variant: confirm ILIM & dead-time.
Output capacitor (ESR & capacity)
- ΔV ≈ (Iout·D)/(Cout·fSW) + Iout·ESR.
- MLCC for ripple + modest ESR for damping; watch DC-bias & temp drift.
Input capacitor
- Place HF MLCC tight to VIN/PGND; add bulk for low-frequency energy.
- Minimize VIN→switch→PGND loop area.
UVLO setting
- VUVLO ≈ Vref·(1 + Rtop/Rbot), add hysteresis if available.
- Place 5–10% above system brown-out; validate cold-crank.
Suppress ringing & overshoot
- RC snubber at switch node; shortest high di/dt loop.
- Soft-start; check diode recovery; clean return paths.
Loop compensation
- Target fc ≈ 0.1–0.2·fSW, PM ≥ 45–60°.
- Type-II (current-mode) / Type-III (voltage-mode); verify with Bode.
Typical Application Scenarios
Where to use a monolithic boost regulator IC: automotive 5/12 V from 3.3 V ECU, portable medical, industrial 24 V stabilization, and drone/robotics power stages.
Automotive sensors — 3.3 V ECU → 5 V/12 V
- I/O: Vin=3.0–3.6 V; Vout=5/12 V; Iout=0.2–1 A; −40~125 °C.
- IC: low Iq; PFM; high-temp; AEC-Q100.
- Board: TVS, PG chain, EMI pre-scan, thermal path.
Portable medical — Battery → 5 V / 9 V
- I/O: Vin=2.7–4.2 V; Vout=5/9 V; Iout=0.5–2 A.
- IC: low noise; PFM with FPWM option; OVP/short.
- Board: audible noise care; ESR/comp tuning; medical EMI.
Industrial — 24 V stabilization
- I/O: Vin=18–30 V; Vout=24–36 V; Iout=0.3–1.5 A.
- IC: higher voltage; UVLO/OVP; thermal; EMI.
- Board: surge/ESD; CM noise control; grounding discipline.
Drone & robotics — 2S–6S → 12–24 V
- I/O: Vin=2S–6S; Vout=12–24 V; Iout=0.5–3 A.
- IC: high efficiency; PFM w/ PWM lock; robust ILIM & thermal.
- Board: shortest switch loop; damp resonances; secure magnetics.
Performance Optimization
Practical methods for EMI reduction, burst-mode/PFM noise control, thermal design and PFM ripple management in a monolithic boost regulator IC, including the use of spread spectrum switching frequency (fSW).
EMI (conducted & radiated)
- Diagnose: identify base fSW and harmonics; separate common-mode vs differential-mode paths.
- Mitigate: shorten switch loop, use shielded inductor, add input π filter (with damping), optimize return paths.
- Spread spectrum: enable fSW dither to move energy across bins and lower peak amplitudes.
Burst-mode noise & PFM ripple management
- Diagnose: audible tones or low-frequency ripple at very light load.
- Mitigate: add minimum load, lock to forced-PWM, increase Cout or adjust ESR, tune compensation, limit minimum on-time.
- Transition: choose PFM↔PWM thresholds to avoid mode-hopping jitter in the audio band.
Thermal design & package heat spreading
- Use exposed-pad packages with copper planes and via arrays to ground.
- Place inductor and rectifier for airflow and thermal isolation; select low DCR to cut I2R loss.
- Derate at high ambient; validate −40~125 °C cycles and thermal shutdown recovery.
- Probe setup and cable routing documented.
- Enable spread spectrum; sweep fSW ±5–10% if supported.
- Add CM choke and damped π filter if peaks persist.
- −40~125 °C chamber with worst-case load/duty.
- Record TSD trigger and recovery; build derating curves.
- Verify copper/via changes vs hotspot temperature.
IC Selection Matrix — Automotive & Industrial
Compare monolithic boost regulator ICs across major brands. Values are illustrative placeholders for structure and SEO; please replace with datasheet-verified numbers during editorial pass.
Tip: use badges to spot fit — Auto Low-Iq High-V
| Brand | Part number | Vin range (V) | Vout max (V) | Iout max (A) | fSW (kHz/MHz) | Light-load | Protections | Sync/Diode | Spread-spectrum | Iq (µA) | Package | Temp grade | AEC-Q100 | Notes / Advantages |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Texas Instruments | TPS61088 Auto | ~2.7–12 | ~12 | ~4 | ~400–2200 | Auto PFM/PWM | UVLO/OVP/TSD/ILIM | Diode | Option | Low | QFN | −40~125 °C | Yes | High current monolithic; robust protection set. |
| STMicroelectronics | STxxxxx Auto | — | — | — | — | PFM/FPWM | UVLO/OVP/TSD | Diode/SR | Option | — | QFN/QFPN | −40~125 °C | Yes | Automotive coverage; good EMC app notes. |
| onsemi | NCPxxxx Auto | — | — | — | — | Auto | UVLO/OVP/TSD/ILIM | Diode/SR | Option | — | DFN/QFN | −40~125 °C | Yes | Solid industrial docs; EMC reference designs. |
| Renesas | ISL/LTxxxx Low-Iq | — | — | — | — | PFM/Auto | UVLO/OVP/TSD | Diode/SR | Option | Very low | DFN/QFN | −40~125 °C | Select | Low quiescent current options for battery systems. |
| NXP | MCxxxx Auto | — | — | — | — | Auto/FPWM | UVLO/OVP/TSD | Diode/SR | — | — | HVQFN | −40~125 °C | Yes | Automotive interfaces and safety docs align well. |
| Microchip | MCPxxxx Low-Iq | — | — | — | — | PFM/Auto | UVLO/OVP/TSD | Diode | — | Very low | DFN/MSOP | −40~105 °C | Select | Battery-friendly Iq; compact packages. |
| Analog Devices (ADI/LTC) | LTxxxx High-V | — | — | — | — | PFM/FPWM | UVLO/OVP/TSD/ILIM | SR/Diode | Option | Low | LQFN/QFN | −40~125 °C | Select | High-voltage and precision options; strong app notes. |
AEC-Q100 grades, PG/diagnostics pins, EMC guides and spread-spectrum options for CISPR pre-scan.
Higher Vin ratings, robust protections, thermal headroom, and long-lifecycle packages.
FAQs — Monolithic Boost Regulator IC
Practical answers to common questions on PFM/PWM transition, UVLO/OVP, startup, ripple/noise, and typical applications. Each answer includes a link back to the detailed section.
