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Analog Devices Inc./Maxim Integrated MAX42403AFLB+T
- Part No.:
- MAX42403AFLB+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 15-PowerWFQFN
- Datasheet:
-
MAX42403AFLB+T.pdf
- Description:
- IC REG BUCK ADJ 3.5A 15FC2QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,041
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Product details
Overview
MAX42403AFLB+T from Analog Devices is a fully integrated, 36V-input synchronous buck converter delivering up to 3.5A output current with 1.5MHz fixed 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 compact industrial point-of-load regulation in space-constrained 24V/36V systems.
For engineers reviewing the MAX42403AFLB+T datasheet, MAX42403AFLB+T pinout, MAX42403AFLB+T application, or MAX42403AFLB+T equivalent, key selection considerations include its 1.5MHz operation enabling small external inductors (e.g., 2.2µH), 99% dropout capability, 27µA no-load quiescent current in skip mode, and FC2QFN-15 package thermal performance (θJA = 40°C/W on multilayer EV kit).
Technical Context
The MAX42403AFLB+T employs average current-mode control with fixed 1.5MHz oscillator and optional external synchronization via SYNC pin. Its architecture supports forced-PWM or automatic skip-mode operation, with internal slope compensation ensuring stability across input/output ranges.
It integrates a 1.8V BIAS LDO (with 1.63V UVLO threshold), precision enable logic (200mV hysteresis), and windowed PGOOD (93–105% VOUT tolerance) with 70–180µs debounce. Protection includes hiccup-mode short-circuit response, overtemperature shutdown (175°C), 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 DC rails including 24V and 36V nominal systems without pre-regulation. |
| Output Current | Up to 3.5A - enables direct powering of FPGA I/O banks, microcontroller cores, or industrial sensors without external current boosting. |
| Switching Frequency | 1.5MHz (fixed) - allows use of sub-3µH inductors and <50µF ceramic output capacitance, reducing solution footprint by >40% vs. 400kHz alternatives. |
| Output Voltage Range | 0.8V to 12V (adjustable) - covers common logic rails (1.2V, 1.8V, 3.3V, 5V, 12V) with 0.8V reference for low-voltage core supplies. |
| Quiescent Current | 27µA (skip mode, no load) - extends battery life in always-on industrial monitoring nodes and reduces standby power loss. |
| Thermal Performance | θJA = 40°C/W (4-layer EV kit) - enables 3.5A continuous operation at +85°C ambient without forced airflow when properly heatsinked. |
| PGOOD Accuracy | ±2.25% window (93–105% VOUT) - provides reliable system-level power sequencing and fault detection for safety-critical PLC modules. |
Pinout & Package
MAX42403AFLB+T is housed in a 3mm × 3mm, 15-pin FC2QFN package with exposed thermal pad (Package Code: F153B3F+1F). The symmetrical pinout minimizes EMI by balancing high-di/dt current loops, and the exposed pad must be soldered to a thermal plane for optimal junction-to-board heat transfer.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN | Enable input | High-voltage-tolerant (up to 42V) active-high logic input; enables internal BIAS LDO and converter startup when pulled above 0.9V. |
| SUP (Pins 3,7) | High-side supply input | Power source for internal gate drivers and high-side FET; requires dual bypass (0.1µF + 2.2µF ceramic) per pin for low-impedance switching current return. |
| PGND (Pins 4,6) | Power ground | Low-impedance return path for high-current LX switching node; must be directly connected to thermal pad and input/output capacitors. |
| LX | Switch node | Connection to inductor's switched side; carries full AC ripple current and high dv/dt transients - requires minimal trace area and tight layout to PGND. |
| BST | Bootstrap capacitor terminal | Connects 0.1µF ceramic capacitor to LX to generate gate drive voltage for high-side FET; critical for stable 100% duty-cycle operation. |
| BIAS | Internal LDO output | 1.8V regulated supply for analog circuitry; requires ≥2.2µF ceramic capacitor to PGND for noise immunity and transient response. |
| FB | Voltage feedback input | Monitors output via resistor divider (RTOP/RBOT); 0.8V reference enables precise output setting with <±1.5% total error over temperature. |
| PGOOD | Open-drain status output | Asserts high when VOUT is within 93–105% of target; requires external pull-up (e.g., 20kΩ to BIAS) for system power-good signaling. |
| SYNC | Mode/frequency control | Pulled low → skip mode; pulled high → forced PWM; driven with external clock → synchronized operation - enables EMI compliance in noise-sensitive environments. |
| SPS | Spread-spectrum enable | Logic-high enables ±6% triangular frequency modulation - reduces peak radiated emissions by up to 10dB without affecting regulation performance. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 3.5A power stage | Eliminates external MOSFETs and gate drivers - reduces BOM count by 6+ components and PCB area by >30% vs. controller-based solutions. |
| 1.5MHz fixed-frequency operation | Enables use of 2.2µH inductors and 42µF ceramic output caps - achieves <1mm² solution height and <150mm² total footprint in typical 3.3V/3.5A designs. |
| 99% maximum duty cycle | Supports operation with <1V input-to-output differential (e.g., 12.1V→12V), critical for maintaining regulation during brownout in 12V industrial buses. |
| Hiccup-mode short-circuit protection | Disables output for 25ms (10× soft-start time) then retries - prevents thermal runaway while allowing automatic recovery after fault removal. |
| Internal soft-start (3.5ms) | Linearly ramps output voltage to limit inrush current into large output capacitors - avoids tripping upstream fuses or causing bus droop in distributed power systems. |
Applications
| Industrial PLC I/O Modules | Factory Automation Sensors |
|---|---|
Use Scenario: Powering isolated digital I/O channels and analog sensor front-ends in modular programmable logic controllers operating from 24VDC field buses. IC Role / Device Role / Timing Role: Primary point-of-load regulator delivering stable 3.3V/3.5A to FPGA configuration banks and isolated RS-485 transceivers. Use Value: 99% duty cycle maintains regulation during 24V bus dips to 22.5V; spread-spectrum EMI reduction meets EN 61000-6-4 Class A limits in dense rack-mounted enclosures. | Use Scenario: Compact power supply for wireless vibration sensors and IIoT edge nodes deployed in harsh factory environments with wide ambient temperature swings. IC Role / Device Role / Timing Role: Single-chip 12V→3.3V conversion with ultra-low 27µA skip-mode IQ for multi-year battery life in energy-harvesting configurations. Use Value: -40°C to +125°C rated operation ensures reliability in uncontrolled machinery cabinets; FC2QFN thermal pad enables passive cooling without heatsinks. |
| Railway Onboard Electronics | Test & Measurement Equipment |
Use Scenario: Powering FPGA-based signal acquisition units in rolling stock electronics where input voltage varies from 24V to 36V due to battery charging transients. IC Role / Device Role / Timing Role: High-efficiency buck stage converting 36V nominal train battery to 1.2V core voltage for ARM Cortex-A processors. Use Value: 4.5V–36V input range accommodates cold-cranking dips and alternator surges; overvoltage protection discharges output rapidly if feedback loop fails. | Use Scenario: Low-noise auxiliary supply in portable oscilloscopes and spectrum analyzers requiring clean 5V/3.5A for ADC reference and clock distribution circuits. IC Role / Device Role / Timing Role: Synchronous buck regulator with forced-PWM mode selected via SYNC pin to eliminate frequency sidebands in sensitive analog signal paths. Use Value: 1.5MHz fixed frequency places switching harmonics beyond 10MHz - avoids interference with RF front-end bandwidth and improves ENOB in 12-bit+ data converters. |
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 die, 400kHz switching frequency, 0.8V–14V output range | Better suited for higher-output-capacitance, lower-EMI designs where 400kHz allows larger inductors and reduced core loss | Select MAX42403AFLA+ when board space permits larger magnetics and EMI filtering is prioritized over minimum footprint. |
| TPS543620RTWR | TI part: 36V input, 3.5A, 1.5MHz, but uses external compensation and lacks integrated spread-spectrum | Requires additional loop compensation components and external EMI filters to match MAX42403AFLB+T's radiated emission performance | Choose TPS543620RTWR only if existing TI ecosystem tools (WEBENCH, PSPICE models) are required and layout resources allow added complexity. |
Compared with MAX42403AFLA+, the MAX42403AFLB+T trades wider output voltage range (14V→12V) for higher switching frequency (1.5MHz), enabling smaller passives; versus TPS543620RTWR, it delivers superior out-of-box EMI performance and reduced design iteration cycles due to full integration and spread-spectrum.
Availability
MAX42403AFLB+T is available at Aetrix Electronics and suitable for industrial automation, point-of-load regulation, and distributed DC power systems requiring stable component supply across extended temperature and voltage ranges.
Supply support for MAX42403AFLB+T 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 with precision power, sensing, and signal chain solutions.
The MAX42402/MAX42403 product line was developed to address demand for ultra-compact, high-reliability DC-DC converters in space-constrained industrial and transportation equipment - emphasizing integrated protection, wide VIN, and EMI robustness without external complexity.
FAQ
What is the maximum output current capability of the MAX42403AFLB+T under continuous operation?
The MAX42403AFLB+T delivers up to 3.5A continuous output current when thermally managed per the datasheet layout guidelines - specifically with θJA ≤ 40°C/W on a 4-layer evaluation board and ambient temperature ≤ +85°C. Derating applies above +85°C ambient; at +105°C, maximum sustainable current drops to approximately 2.4A based on thermal shutdown threshold (175°C) and hysteresis (15°C).
Does the MAX42403AFLB+T support external frequency synchronization, and what are the valid input ranges?
Yes, the MAX42403AFLB+T supports external synchronization via the SYNC pin. When configured for external clock mode, it accepts frequencies from 360kHz to 600kHz (for 400kHz internal base) or 1.215MHz to 1.845MHz (for 1.5MHz internal base). The device locks to the external clock within two cycles at the rising edge, and reverts to internal oscillation if the external signal is absent for more than two cycles.
How does the spread-spectrum feature of the MAX42403AFLB+T reduce EMI, and is it compatible with external synchronization?
The MAX42403AFLB+T's spread-spectrum feature modulates the switching frequency by ±6% using a triangular waveform (300µs period at 1.5MHz), spreading energy across a band instead of concentrating at discrete harmonics. This reduces peak radiated emissions by up to 10dB. Spread-spectrum is automatically disabled when SYNC is driven by an external clock - the device operates at the fixed external frequency without modulation.
What is the purpose of the BIAS pin on the MAX42403AFLB+T, and how should it be decoupled?
The BIAS pin on the MAX42403AFLB+T outputs a regulated 1.8V supply used internally for analog circuitry and gate drivers. It must be decoupled with ≥2.2µF ceramic capacitance connected directly to PGND, placed as close as possible to the pin. This ensures stable bias voltage during load transients and suppresses noise coupling into the feedback and control loops - failure to meet this requirement risks PGOOD false triggering or erratic soft-start behavior.
Can the MAX42403AFLB+T operate in dropout mode, and what is the minimum input-to-output voltage differential supported?
Yes, the MAX42403AFLB+T supports dropout operation with up to 99% duty cycle, enabling regulation when input voltage approaches output voltage. At 12V output, it maintains regulation down to ~12.12V input (12V ÷ 0.99), supporting operation during 24V bus brownouts to 22.5V in 12V-output configurations. Dropout performance is validated across temperature and load, with no minimum VIN–VOUT specification beyond the 99% duty cycle limit.
MAX42403AFLB+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 15-PowerWFQFN
- Packaging:
- Tape & Reel (TR)
- 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+T FAQ
1.How can I place an order for MAX42403AFLB+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX42403AFLB+T 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+T reliable?
The price and inventory of MAX42403AFLB+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX42403AFLB+T is usually 5 days.
3.What payment methods are accepted for MAX42403AFLB+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX42403AFLB+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX42403AFLB+T?
MAX42403AFLB+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX42403AFLB+T 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+T?
For technical support, including MAX42403AFLB+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX42403AFLB+T requirements.
6.How does Aetrix verify that MAX42403AFLB+T is sourced from the original manufacturer or authorized distributors?
All MAX42403AFLB+T 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+T meets industry standards.
7.What is the process for return or replacement of MAX42403AFLB+T?
All MAX42403AFLB+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX42403AFLB+T, 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+T part is unused and in its original packaging.
Return procedure for MAX42403AFLB+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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