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Analog Devices Inc./Maxim Integrated MAX42403AFLB+
- Part No.:
- MAX42403AFLB+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 15-PowerWFQFN
- Datasheet:
-
MAX42403AFLB+.pdf
- Description:
- IC REG BUCK ADJ 3.5A 15FC2QFN
- Quantity:
- Payment:
- Shipping:
Inventory:367
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Product details
Overview
MAX42403AFLB+ from Analog Devices is a fully integrated, 36V-input synchronous buck converter delivering up to 3.5A output current with fixed 1.5MHz switching frequency and adjustable 0.8V–12V output voltage. It integrates high-side and low-side MOSFETs, internal soft-start (3.5ms), spread-spectrum EMI reduction (±6%), and precision PGOOD monitoring. Designed for industrial point-of-load regulation where wide VIN, compact size, and robust protection are critical.
For engineers reviewing the MAX42403AFLB+ datasheet, MAX42403AFLB+ pinout, MAX42403AFLB+ application, or MAX42403AFLB+ equivalent, key selection considerations include its 1.5MHz/3.5A/12V-adjustable capability, FC2QFN-15 package, 99% dropout duty cycle, 27μA skip-mode quiescent current, and integrated thermal/overvoltage/short-circuit protection - all validated for -40°C to +125°C operation.
Technical Context
The MAX42403AFLB+ employs average current-mode control with fixed 1.5MHz oscillator and ±6% spread-spectrum modulation to suppress EMI peaks. Its architecture includes internal slope compensation, 37ns minimum on-time, and 99% maximum duty cycle for ultra-low dropout operation.
It features dual undervoltage lockout (UVLO) thresholds - programmable via external resistor divider on EN - and windowed PGOOD with 93% UV and 105% OV detection thresholds. Protection includes hiccup-mode short-circuit response (25ms off-time), thermal shutdown at 175°C with 15°C hysteresis, and overvoltage discharge via low-side FET activation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 36V - supports wide industrial rails including 24V and 36V systems without pre-regulation. |
| Output Current | Up to 3.5A continuous - enables single-chip power delivery for FPGA I/O, PLC modules, and sensor interfaces. |
| Switching Frequency | Fixed 1.5MHz - allows use of sub-3μH inductors (e.g., 2.2μH typical) and reduces output capacitor count. |
| Output Voltage Range | 0.8V to 12V (adjustable via FB resistor divider) - covers core logic, analog, and interface rail requirements. |
| Quiescent Current | 27μA in skip mode - extends battery life in always-on industrial sensors and remote I/O nodes. |
| PGOOD Accuracy | ±2.25% UV/OV window (93%–105%) - provides reliable system-level power sequencing and fault reporting. |
| Thermal Shutdown | 175°C with 15°C hysteresis - ensures safe recovery after overload or poor heatsinking in enclosed enclosures. |
| Package | 3mm × 3mm FC2QFN-15 - enables <100mm² total solution size with symmetrical layout for EMI cancellation. |
Pinout & Package
MAX42403AFLB+ uses a 3mm × 3mm, 15-pin FC2QFN package with exposed thermal pad (pin 15 = PGND). The symmetrical SUP/PGND pin arrangement minimizes loop inductance and improves EMI performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN (Pin 1) | Enable input | High-voltage-tolerant (up to 42V); activates BIAS LDO and converter when >0.9V; supports programmable UVLO via external divider. |
| SUP (Pins 3,7) | High-side supply input | Power source for internal gate drivers and logic; requires local 0.1μF + 2.2μF ceramic bypass per pin for stability and EMI suppression. |
| PGND (Pins 4,6,15) | Power ground | Low-impedance return path for high-current LX switching; must be connected directly to thermal pad and external bulk capacitors. |
| LX (Pin 5) | Switch node | Connects to inductor; carries full switching current (3.5A RMS); requires minimal trace area to reduce radiated EMI. |
| BST (Pin 9) | Bootstrap capacitor connection | Drives high-side FET gate; requires 0.1μF ceramic capacitor between BST and LX; placement critical for gate drive integrity. |
| BIAS (Pin 11) | Internal 1.8V LDO output | Powers internal circuitry; requires ≥2.2μF ceramic capacitor to PGND; serves as PGOOD pull-up source. |
| SPS (Pin 12) | Spread-spectrum enable | Logic-high enables ±6% triangular frequency modulation; disabled during external SYNC; reduces peak EMI by >10dB. |
| FB (Pin 13) | Feedback input | 0.8V reference input; sets output via resistor divider; leakage <100nA ensures accuracy across temperature. |
| PGOOD (Pin 14) | Open-drain power-good | Active-high signal pulled low if VOUT <93% or >105%; requires external 20kΩ pull-up to BIAS or system rail. |
| SYNC (Pin 15) | Mode control & sync input | Low = skip mode; high = forced PWM; external clock input (1.215–1.845MHz) enables system-wide timing synchronization. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 96mΩ HS / 46mΩ LS FETs | Enables 3.5A output without external MOSFETs or gate drivers; reduces BOM count and layout complexity. |
| 3.5ms internal soft-start (1.5MHz) | Prevents inrush current damage to input capacitors and downstream loads during power-up. |
| 99% dropout duty cycle | Maintains regulation down to VIN – VOUT = 0.36V (e.g., 12.36V IN → 12V OUT), critical for brownout resilience. |
| Hiccup-mode short-circuit protection | Shuts down for 25ms then retries - prevents thermal runaway while enabling automatic recovery after fault removal. |
| Symmetrical FC2QFN pinout | Equal-length SUP/PGND paths cancel magnetic fields, reducing common-mode EMI by up to 6dB vs asymmetric layouts. |
| 1.8V BIAS regulator with UVLO | Stable internal supply with 1.63V turn-on threshold and 65mV hysteresis - ensures clean startup under varying input conditions. |
Applications
| Industrial PLC I/O Modules | Factory Automation Sensors |
|---|---|
Use Scenario: Powering isolated digital I/O, analog input channels, and CAN transceivers in DIN-rail mounted PLC backplanes with 24V DC input. IC Role / Device Role / Timing Role: Primary point-of-load regulator converting 24V to 3.3V/5V/12V rails with tight transient response and immunity to motor-drive EMI. Use Value: 1.5MHz switching enables compact 2.2μH inductor and 42μF output capacitance; spread-spectrum and symmetrical layout meet EN 61000-6-4 Class A emissions limits. | Use Scenario: Supplying low-power wireless sensor nodes (LoRaWAN, NB-IoT) deployed in harsh factory environments with wide ambient temperature swings. IC Role / Device Role / Timing Role: Always-on buck converter powering MCU, RF SoC, and analog front-end from 12–36V battery or energy-harvesting sources. Use Value: 27μA skip-mode IQ extends battery life to >5 years; -40°C to +125°C rating ensures reliability in uncontrolled enclosures; PGOOD enables predictive maintenance alerts. |
| Ruggedized HMI Displays | Motor Drive Auxiliary Supplies |
Use Scenario: Generating 5V and 12V rails for touch-screen controllers, backlight drivers, and USB peripherals in panel-mounted HMIs exposed to vibration and thermal cycling. IC Role / Device Role / Timing Role: Dual-rail power manager with independent feedback loops (via resistor networks) and coordinated PGOOD signaling. Use Value: 99% duty cycle maintains 12V output even during 24V brownouts; thermal shutdown + hysteresis prevents latch-up during prolonged overloads near enclosure walls. | Use Scenario: Providing isolated gate-driver and MCU supplies in servo drives where main DC bus ranges from 20V to 36V under regenerative braking. IC Role / Device Role / Timing Role: Robust auxiliary supply tolerant of high dv/dt noise and bus voltage transients exceeding 40V. Use Value: 42V absolute max SUP rating and 1.5MHz operation minimize coupling of switching noise into sensitive gate-drive paths; FC2QFN thermal pad dissipates >2W at 40°C/W ambient. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX42403AFLA+ | Same IC, but 400kHz switching and 0.8V–14V output range; higher inductance (6.8μH) and larger output caps required. | Better suited for noise-sensitive analog circuits where lower switching frequency eases filtering; less compact than MAX42403AFLB+. | Select MAX42403AFLA+ when EMI filtering priority outweighs board space constraints and 14V output is needed. |
| TPS543320RHLR | 36V, 3.5A, 1.5MHz buck with PMBus interface; no integrated spread-spectrum; requires external compensation. | Targeted at digitally controlled power systems needing telemetry and dynamic margining; lacks PGOOD windowing and hiccup-mode protection. | Choose TPS543320RHLR only when digital configuration and telemetry are mandatory; MAX42403AFLB+ offers simpler analog design with superior protection integration. |
Compared with MAX42403AFLA+, MAX42403AFLB+ trades 2V output headroom for 3× smaller magnetics and tighter EMI control; versus TPS543320RHLR, it delivers plug-and-play operation with no firmware or compensation tuning, at the cost of configurability.
Availability
MAX42403AFLB+ is available at Aetrix Electronics and suitable for industrial automation, point-of-load regulation, and distributed DC power systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for MAX42403AFLB+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets since 1965.
The MAX42402/MAX42403 family was designed specifically for space-constrained industrial point-of-load applications demanding wide-input, high-efficiency, and robust protection - with MAX42403AFLB+ optimized for 1.5MHz/3.5A/12V systems.
FAQ
What is the maximum output voltage supported by MAX42403AFLB+?
The MAX42403AFLB+ supports an adjustable output voltage range of 0.8V to 12V, confirmed in the Ordering Information table and Electrical Characteristics section for 1.5MHz operation. This limit is enforced by internal design constraints - attempting to set above 12V using the FB divider will result in regulation loss or instability. The 12V ceiling ensures safe operation of internal gate drivers and maintains specified current-limit accuracy.
Does MAX42403AFLB+ require external compensation components?
No, MAX42403AFLB+ does not require external compensation components. It uses an internally compensated average current-mode control architecture with fixed gain and pole-zero placement optimized for stability with recommended inductors (e.g., 2.2μH at 1.5MHz) and output capacitors (e.g., 42μF ceramic). The datasheet's Typical Application Circuits confirm zero external compensation parts - only FB resistors, input/output capacitors, inductor, BST cap, and CFF (feed-forward) are needed.
How does the spread-spectrum feature work on MAX42403AFLB+?
When SPS pin is high, MAX42403AFLB+ enables triangular spread-spectrum modulation that varies the 1.5MHz switching frequency by ±6% (±90kHz) with a 300μs period. This spreads EMI energy across a bandwidth instead of concentrating at harmonics, reducing peak radiated emissions by up to 10dB. Spread-spectrum is automatically disabled during external SYNC operation, and the modulation waveform is generated internally - no external clock or programming is required.
What is the purpose of the dual PGND pins (4, 6) and thermal pad (15) on MAX42403AFLB+?
Pins 4 and 6 are dedicated power ground terminals for high-current return paths from the internal low-side FET and input capacitors, while pin 15 is the exposed thermal pad connected to internal PGND. This triple-point grounding minimizes impedance in the high-di/dt LX-PGND loop, reduces voltage spikes during switching transitions, and enhances thermal dissipation. Layout guidelines mandate connecting all three to a solid copper plane - separating them causes instability and EMI degradation.
Can MAX42403AFLB+ operate with input voltage below 4.5V?
No, MAX42403AFLB+ cannot operate reliably below 4.5V input. Its absolute minimum operating supply voltage is 4.5V, as specified in Electrical Characteristics and General Description. Below this, the internal BIAS regulator fails to start, gate drive voltage collapses, and the device remains in shutdown. The 2.9V–3.15V UVLO threshold applies only to the EN pin's enable function - it does not extend operational range below 4.5V VIN.
MAX42403AFLB+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 15-PowerWFQFN
- Packaging:
- Tray
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 12V
- Current - Output:
- 3.5A
- Frequency - Switching:
- 1.5MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount, Wettable Flank
- Supplier Device Package:
- 15-FC2QFN (3x3)
MAX42403AFLB+ FAQ
1.How can I place an order for MAX42403AFLB+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX42403AFLB+ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MAX42403AFLB+ reliable?
The price and inventory of MAX42403AFLB+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX42403AFLB+ is usually 5 days.
3.What payment methods are accepted for MAX42403AFLB+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX42403AFLB+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX42403AFLB+?
MAX42403AFLB+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX42403AFLB+ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MAX42403AFLB+?
For technical support, including MAX42403AFLB+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX42403AFLB+ requirements.
6.How does Aetrix verify that MAX42403AFLB+ is sourced from the original manufacturer or authorized distributors?
All MAX42403AFLB+ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MAX42403AFLB+ meets industry standards.
7.What is the process for return or replacement of MAX42403AFLB+?
All MAX42403AFLB+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX42403AFLB+, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MAX42403AFLB+ part is unused and in its original packaging.
Return procedure for MAX42403AFLB+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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