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Analog Devices Inc./Maxim Integrated MAX1945SEUI+
- Part No.:
- MAX1945SEUI+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
MAX1945SEUI+.pdf
- Description:
- IC REG BUCK ADJ 6A 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,068
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Product details
Overview
MAX1945SEUI+ from Maxim Integrated is a 6A synchronous step-down DC-DC regulator with internal dual N-channel MOSFETs, operating from 2.6V–5.5V input and delivering adjustable output (0.8V to 85% VIN) or preset 1.8V/2.5V. It achieves ±1% total output voltage error over load, line, and temperature, supports 500kHz/1MHz fixed-frequency or external synchronization (400kHz–1.2MHz), and provides ±9% voltage margining for board-level testing. It is used in high-density post-regulation for ASIC/CPU core supplies.
For engineers reviewing the MAX1945SEUI+ datasheet, MAX1945SEUI+ pinout, MAX1945SEUI+ application, or MAX1945SEUI+ equivalent, key selection considerations include its 28-pin TSSOP-EP package, 6A RMS output capability, ±9% margining control via CTL1/CTL2, internal current-sense transresistance of 43–65mΩ, and thermal shutdown at 165°C with 20°C hysteresis.
Technical Context
The MAX1945SEUI+ implements current-mode PWM control with integrated slope compensation to prevent subharmonic oscillation and inductor staircasing. Its internal error amplifier delivers high bandwidth for fast transient response, and the dual N-channel synchronous rectifier eliminates external Schottky diodes while reducing conduction losses.
It features digital soft-start (3.7ms typical), undervoltage lockout (VUVLO rising = 2.55V, falling = 2.20V), and pulse-skip mode during short-circuit conditions (activated when FB < 300mV). The device supports out-of-phase operation with a second MAX1945R/S via SYNCOUT to minimize input capacitance ripple.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 6A RMS - supports high-current ASIC/CPU core rails without external MOSFETs |
| Input Voltage Range | 2.6V to 5.5V - compatible with single-cell Li-ion, 3.3V, and 5V intermediate bus architectures |
| Output Voltage Accuracy | ±1% over load, line, and temperature - ensures stable core voltage under dynamic load and thermal drift |
| Switching Frequency | Selectable 500kHz or 1MHz, or syncable 400kHz–1.2MHz - enables optimization of size vs. efficiency and EMI filtering |
| Voltage Margining | ±9% (MAX1945S variant) - enables precise functional margin testing of downstream logic without hardware changes |
| LX On-Resistance | High-side: ≤50mΩ, Low-side: ≤50mΩ at VIN = 2.6V - minimizes conduction loss and thermal rise at full load |
| Thermal Shutdown | 165°C threshold with 20°C hysteresis - protects against sustained overload while enabling automatic recovery |
Pinout & Package
MAX1945SEUI+ is housed in a 28-pin TSSOP-EP (Exposed Pad) package, thermally enhanced for high-power density applications. The exposed pad must be soldered to PGND for optimal thermal performance and electrical stability.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BST (Pin 1) | Bootstrap supply for high-side gate driver | Requires 0.1µF capacitor to LX and Schottky diode from IN; enables efficient N-channel high-side switching |
| VDD (Pin 2) | Low-side MOSFET gate driver supply | Provides dedicated bias for synchronous rectifier; decoupled separately from VCC |
| LX (Pins 3,5,7,9,20,22,24,26) | Switch node connection to power inductor | Multiple parallel pins reduce current density and parasitic inductance; must be star-connected near device |
| IN (Pins 4,6,8,10) | Main input power supply (2.6V–5.5V) | Four pins support high-current input path; requires three 22µF ceramic caps to PGND for low-impedance bypass |
| VCC (Pin 11) | Internal logic and bias supply | Powered via 10Ω resistor from IN; bypassed with 0.1µF cap to GND for noise immunity |
| GND (Pin 12) | Analog ground reference | Separate from PGND; connects to REF/COMP/FB analog circuitry to avoid noise coupling |
| REF (Pin 13) | Soft-start and margining reference ramp | Bypassed with 0.22µF cap; pulled to GND in shutdown; tracks margining commands |
| COMP (Pin 14) | Error amplifier output for loop compensation | Connects RC network to GND; clamped between 0.5V–2.4V; pulled to GND in shutdown |
| FB (Pin 15) | Feedback input for output voltage regulation | Accepts direct connection (1.8V/2.5V) or resistor divider (0.8V–85% VIN); 0.1µA max bias current |
| FBSEL (Pin 16) | Output voltage selection control | High-Z → adjustable mode; GND → 1.8V; VCC → 2.5V - sets internal reference without external resistors |
| SYNC (Pin 17) | Frequency select/synchronization input | GND → 500kHz; VCC → 1MHz; external clock 400kHz–1.2MHz - enables multi-phase or EMI-controlled timing |
| SYNCOUT (Pin 18) | 180° out-of-phase clock output | Drives second MAX1945R/S to halve input ripple current and reduce required bulk capacitance |
| PGND (Pins 19,21,23,25) | Power ground return for high-current paths | Four pins for low-inductance return; star-connected to GND at single point near exposed pad |
| CTL1 / CTL2 (Pins 27–28) | Voltage margining and enable control | GND/GND → shutdown; VCC/VCC → nominal; VCC/GND → –9%; GND/VCC → +9% - no external DAC needed |
| EP (Exposed Pad) | Thermal and electrical ground connection | Must be soldered to solid PGND plane; primary path for heat dissipation and noise reduction |
Key Features
| Feature | Design Value |
|---|---|
| 6A internal synchronous switch | Eliminates external MOSFETs and Schottky diodes, reducing BOM count and PCB area by >30% vs. controller-based solutions |
| ±9% precision voltage margining | Enables automated production test of system-level voltage tolerance without firmware or external instrumentation |
| 180° SYNCOUT for dual-phase operation | Allows two MAX1945SEUI+ units to share input capacitance and cut peak input ripple current by ~70% |
| All-ceramic capacitor compatibility | Supports low-ESR/ESL ceramic output caps only - simplifies layout, improves transient response, and avoids electrolytic aging |
| Digital soft-start (3.7ms typical) | Prevents inrush current surges during power-up, eliminating need for external soft-start ICs or RC timers |
Applications
| ASIC Core Power Supply | CPU Voltage Regulator Module (VRM) |
|---|---|
Use Scenario: Providing tightly regulated 1.8V or adjustable core voltage to high-performance ASICs in telecom baseband processing units. IC Role / Device Role / Timing Role: Primary synchronous buck regulator delivering up to 6A with ±1% accuracy and <100µs transient response to load steps. Use Value: Enables reliable operation under dynamic DVFS workloads while maintaining <±10mV output deviation during 4A/µs load transients. | Use Scenario: Serving as a compact, high-efficiency post-regulator for CPU core voltage in embedded server modules with strict thermal envelope limits. IC Role / Device Role / Timing Role: Single-chip 6A buck converter with integrated MOSFETs and thermal protection, replacing multi-component discrete solutions. Use Value: Reduces solution footprint to 0.76in² and maintains junction temperature <125°C at 6A/5V input even at +85°C ambient. |
| RAM Power Delivery | Networking Equipment Power |
Use Scenario: Supplying 2.5V DDR memory rails in high-speed packet-processing blades where board space and EMI are constrained. IC Role / Device Role / Timing Role: Fixed-output 2.5V buck regulator synchronized to system clock via SYNC pin to suppress switching noise in sensitive analog sections. Use Value: Achieves <15mVpp output ripple at 1MHz sync frequency, meeting JEDEC DDR3/4 VDDQ noise requirements. | Use Scenario: Generating multiple point-of-load voltages in carrier-grade Ethernet switches requiring long-term reliability and margin testing. IC Role / Device Role / Timing Role: Dual-phase-configurable regulator supporting ±9% voltage margining for accelerated life testing and field failure analysis. Use Value: Allows automated burn-in validation at +9% and –9% VOUT without modifying hardware or firmware, cutting test cycle time by 40%. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-current synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP8765GQ-Z (Monolithic Power Systems) | 6A rated, 2.5V–18V input, fixed 500kHz/1MHz, no voltage margining, smaller 20-pin QFN | Lacks ±9% margining and SYNCOUT phase-shift capability; better suited for cost-sensitive non-test applications | Select when margining and dual-phase sync are unnecessary and wider input range is required |
| TPS546B24RVFT (Texas Instruments) | 6A, 3.0V–18V input, PMBus-enabled, 400kHz–2MHz sync, ±0.5% accuracy, no integrated margining | Requires external DAC or GPIO for margining; adds digital telemetry but increases design complexity and BOM | Select when telemetry, programmability, or higher input voltage range outweighs need for integrated margining |
Compared with MP8765GQ-Z and TPS546B24RVFT, MAX1945SEUI+ uniquely integrates ±9% hardware-based voltage margining and 180° SYNCOUT for dual-phase operation-enabling faster board-level validation and lower input capacitor cost without sacrificing accuracy or thermal robustness.
Availability
MAX1945SEUI+ is available at Aetrix Electronics and suitable for ASIC core power, CPU VRM, and networking equipment power supplies requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.
Supply support for MAX1945SEUI+ 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
Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power-management ICs for demanding industrial, computing, and communications applications.
The MAX1945R/MAX1945S product line delivers high-current, high-accuracy synchronous buck regulators optimized for on-board post-regulation in space-constrained systems requiring ±1% output stability and built-in margining for production test.
FAQ
What is the maximum continuous output current supported by the MAX1945SEUI+?
The MAX1945SEUI+ delivers up to 6A RMS output current under specified thermal conditions (TA ≤ +85°C, proper PCB layout with exposed pad soldered to PGND). This rating is validated per the datasheet's "RMS LX Output Current" specification and confirmed in typical operating characteristics plots at 6A load with 1.8V output and 500kHz switching. Derating applies above +70°C ambient due to 23.8mW/°C thermal resistance.
How does the MAX1945SEUI+ implement voltage margining, and what are the control logic states?
The MAX1945SEUI+ implements ±9% hardware-based voltage margining using CTL1 and CTL2 pins. When CTL1 = VCC and CTL2 = GND, output drops to –9%; when CTL1 = GND and CTL2 = VCC, output rises to +9%; both high yields nominal voltage; both low disables the regulator. This is specific to the MAX1945S variant (MAX1945SEUI+) and differs from the ±4% margining of the MAX1945R.
Can the MAX1945SEUI+ operate with only ceramic capacitors on input and output?
Yes, the MAX1945SEUI+ is explicitly designed for all-ceramic capacitor operation. The datasheet confirms compatibility with low-ESR/ESL ceramic input (three 22µF in parallel) and output capacitors. This eliminates electrolytic aging concerns, improves transient response, and reduces solution height to <3mm - a key requirement for ultra-thin computing and networking modules.
What is the purpose of the SYNCOUT pin on the MAX1945SEUI+, and how is it used in practice?
The SYNCOUT pin on the MAX1945SEUI+ provides a 180° out-of-phase clock signal synchronized to the internal switching frequency. In practice, it drives a second MAX1945SEUI+ (or MAX1945REUI+) to configure a dual-phase interleaved supply, reducing input ripple current by ~70% and allowing smaller input bulk capacitance - critical for high-density telecom and server power designs.
Does the MAX1945SEUI+ require an external bootstrap diode, and what type is recommended?
Yes, the MAX1945SEUI+ requires an external Schottky diode from IN to BST to charge the bootstrap capacitor during low-side conduction. The datasheet specifies a 1N4148 diode for 5V input to reduce cost, though low-forward-voltage Schottky diodes (e.g., BAT54) are preferred for <3.3V inputs to maintain sufficient gate drive margin and ensure reliable high-side MOSFET turn-on.
MAX1945SEUI+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable (Programmable)
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.6V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 0.8V (1.8V, 2.5V)
- Voltage - Output (Max):
- 4.68V
- Current - Output:
- 6A
- Frequency - Switching:
- 400kHz ~ 1.2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
MAX1945SEUI+ FAQ
1.How can I place an order for MAX1945SEUI+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1945SEUI+ 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 MAX1945SEUI+ reliable?
The price and inventory of MAX1945SEUI+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1945SEUI+ is usually 5 days.
3.What payment methods are accepted for MAX1945SEUI+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1945SEUI+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1945SEUI+?
MAX1945SEUI+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1945SEUI+ 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 MAX1945SEUI+?
For technical support, including MAX1945SEUI+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1945SEUI+ requirements.
6.How does Aetrix verify that MAX1945SEUI+ is sourced from the original manufacturer or authorized distributors?
All MAX1945SEUI+ 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 MAX1945SEUI+ meets industry standards.
7.What is the process for return or replacement of MAX1945SEUI+?
All MAX1945SEUI+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX1945SEUI+, 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 MAX1945SEUI+ part is unused and in its original packaging.
Return procedure for MAX1945SEUI+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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