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Analog Devices Inc./Maxim Integrated MAX1945REUI+
- Part No.:
- MAX1945REUI+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
MAX1945REUI+.pdf
- Description:
- IC REG BUCK ADJ 6A 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:314
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Product details
Overview
MAX1945REUI+ from Maxim Integrated is a 6A, 1MHz synchronous step-down DC-DC regulator with internal dual N-channel MOSFETs, ±4% voltage margining, ±1% output accuracy over load/line/temperature, and selectable fixed (500kHz/1MHz) or externally synchronized (400kHz–1.2MHz) operation. It delivers stable core power for ASICs, CPUs, and RAM in space-constrained telecom and server applications.
For engineers reviewing the MAX1945REUI+ datasheet, MAX1945REUI+ pinout, MAX1945REUI+ application, or MAX1945REUI+ equivalent, key selection considerations include its 2.6V–5.5V input range, 0.8V–0.85×VIN adjustable output or preset 1.8V/2.5V options, TSSOP-EP thermal performance, and dual-phase synchronization capability.
Technical Context
The MAX1945REUI+ implements current-mode PWM control with integrated slope compensation to ensure loop stability and prevent subharmonic oscillation. Its digital soft-start (3.7ms typical) reduces inrush current, while thermal shutdown at 165°C with 20°C hysteresis protects against sustained overload.
It features dual-control margining inputs (CTL1/CTL2) enabling precise ±4% output deviation for board-level functional testing, and SYNCOUT provides a 180° out-of-phase clock signal to support interleaved two-phase operation with a second MAX1945R/S device-reducing input ripple and minimizing required input capacitance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 6A RMS continuous - supports high-density CPU/ASIC core rails without external MOSFETs |
| Input Voltage Range | 2.6V to 5.5V - compatible with single-cell Li-ion, 3.3V/5V system rails, and post-regulation from intermediate bus |
| Output Accuracy | ±1% over load, line, and temperature - ensures tight regulation across industrial -40°C to +85°C range |
| Switching Frequency | Selectable 500kHz or 1MHz, or 400kHz–1.2MHz sync - enables optimization of size vs. efficiency and EMI filtering |
| Voltage Margining | ±4% (MAX1945R only) - supports production test margining without hardware modification |
| LX On-Resistance | High-side: 43mΩ typ @ 3.3V; Low-side: 43mΩ typ - minimizes conduction loss and thermal rise at full load |
| Thermal Shutdown | 165°C threshold with 20°C hysteresis - prevents permanent damage during sustained overload or poor PCB heatsinking |
Pinout & Package
The MAX1945REUI+ is housed in a 28-pin TSSOP-EP (exposed pad) package optimized for thermal dissipation and high-current routing. The exposed pad must be soldered to PGND for effective heat transfer and low-impedance power ground return.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BST (Pin 1) | Bootstrap supply for high-side gate driver | Requires 0.1µF ceramic capacitor to LX; enables efficient N-channel high-side switching without external charge pump |
| VDD (Pin 2) | Low-side MOSFET gate driver supply | Must be decoupled locally; powers internal synchronous rectifier driver stage |
| LX (Pins 3,5,7,9,20,22,24,26) | Switch node connection to inductor | All eight pins must be shorted together near device; carries high di/dt switching current and requires low-inductance layout |
| IN (Pins 4,6,8,10) | Main input power supply | Accepts 2.6V–5.5V; requires three parallel 22µF ceramic capacitors to PGND for high-frequency decoupling |
| VCC (Pin 11) | Internal logic and bias supply | Powered via 10Ω resistor from IN; bypassed with 0.1µF capacitor to GND for noise immunity |
| REF (Pin 13) | Soft-start and margining reference ramp | Bypassed with 0.22µF capacitor; pulled to GND during shutdown; tracks output margining transitions |
| COMP (Pin 14) | Error amplifier compensation node | Connects external RC network for loop stability; pulled to GND during shutdown |
| FB (Pin 15) | Feedback input for output voltage regulation | Direct connection sets 1.8V (FBSEL=GND) or 2.5V (FBSEL=VCC); resistor divider enables 0.8V–0.85×VIN adjustment |
| FBSEL (Pin 16) | Feedback voltage select control | High-Z = adjustable mode; GND = 1.8V; VCC = 2.5V - determines internal reference used by error amplifier |
| SYNC (Pin 17) | Frequency select/synchronization input | GND = 500kHz; VCC = 1MHz; external clock = 400kHz–1.2MHz with 10%–90% duty cycle |
| SYNCOUT (Pin 18) | 180° out-of-phase synchronization output | Enables interleaved operation with second MAX1945R/S to halve input ripple current and reduce bulk capacitance |
| CTL1/CTL2 (Pins 27–28) | Voltage margining control inputs | Four-state encoding: both GND = off; both VCC = nominal; CTL1=VCC/CTL2=GND = –4%; CTL1=GND/CTL2=VCC = +4% |
| PGND (Pins 19,21,23,25) | Power ground return for high-current paths | Must be star-connected to analog GND; all four pins tied together near device for minimal ground bounce |
Key Features
| Feature | Design Value |
|---|---|
| Integrated dual N-channel MOSFETs | Eliminates need for external high-side/low-side switches and freewheeling diode - reduces BOM count and layout area |
| ±4% precision voltage margining | Enables automated functional testing of downstream logic under over/under-voltage conditions without changing hardware |
| 180° SYNCOUT clock output | Allows seamless interleaving with a second MAX1945R/S to cut input RMS current by ~30% and shrink input capacitor volume |
| 0.76in² complete 6A regulator footprint | Supports ultra-dense board layouts in servers, base stations, and notebooks where PCB real estate is constrained |
| All-ceramic capacitor compatibility | Enables use of low-ESR, low-ESL MLCCs for output filtering - improves transient response and eliminates electrolytic aging concerns |
Applications
| ASIC Core Power Supply | CPU Voltage Regulator Module (VRM) |
|---|---|
Use Scenario: Providing tightly regulated 1.8V core voltage to high-performance ASICs in telecom line cards with strict thermal and space constraints. IC Role / Device Role / Timing Role: Primary synchronous buck converter delivering up to 6A with ±1% accuracy and fast transient response to handle dynamic current steps. Use Value: Internal MOSFETs and 1MHz switching enable compact design; ±4% margining validates ASIC timing margins during production test. | Use Scenario: Serving as a secondary VRM stage supplying 1.8V or 2.5V to embedded microprocessors in industrial controllers. IC Role / Device Role / Timing Role: Post-regulator stepping down intermediate bus (e.g., 5V or 3.3V) to processor core voltage with digital soft-start and thermal protection. Use Value: 3.7ms soft-start prevents inrush-induced rail collapse; TSSOP-EP package ensures reliable thermal performance at 6A continuous load. |
| RAM Power Delivery | Base Station RF Power Amplifier Bias |
Use Scenario: Generating stable 1.8V supply for DDR3/DDR4 memory subsystems in networking switches requiring low-noise, high-current delivery. IC Role / Device Role / Timing Role: High-efficiency DC-DC converter with all-ceramic output filter supporting fast load transients during burst data access. Use Value: 95% peak efficiency minimizes heat near memory banks; ±1% output accuracy maintains memory timing compliance across temperature. | Use Scenario: Delivering precisely controlled 2.5V bias to GaAs/GaN RF power amplifiers in 4G/5G small cell base stations. IC Role / Device Role / Timing Role: Adjustable-output buck regulator configured for 2.5V using FBSEL=VCC, with margining for PA gain calibration verification. Use Value: ±4% voltage margining allows validation of PA linearity and gain flatness across supply tolerance extremes without test fixture rework. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1945SEUI+ | Same pinout and architecture, but ±9% voltage margining instead of ±4% | Suitable for applications requiring wider margining tolerance, e.g., legacy IC validation or high-temperature derating scenarios | Select MAX1945SEUI+ only when ±9% margining is explicitly required; otherwise MAX1945REUI+ offers tighter control for modern ASIC/CPU rails |
| TPS54620RGYR | 6A synchronous buck with 4.5–17V input, no integrated margining, 500kHz–2.2MHz sync range | Targets higher-input industrial systems; lacks dedicated margining pins and REF-based soft-start ramp | Choose TPS54620RGYR for >5.5V input rails or when wider input range outweighs need for built-in margining and low-VIN capability |
Compared with MAX1945SEUI+, the MAX1945REUI+ provides tighter ±4% margining for precision test coverage; compared with TPS54620RGYR, it supports lower 2.6V input and integrates margining control-making it optimal for low-voltage, test-ready embedded power designs.
Availability
MAX1945REUI+ is available at Aetrix Electronics and suitable for telecom infrastructure, server motherboard power, and industrial embedded computing applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for MAX1945REUI+ 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, communications, and computing applications.
The MAX1945R/S product line was engineered specifically for high-current, low-voltage post-regulation in space-constrained systems-emphasizing integration, thermal efficiency, and production testability through features like voltage margining and interleaved synchronization.
FAQ
What is the maximum continuous output current supported by the MAX1945REUI+?
The MAX1945REUI+ delivers up to 6A RMS continuous output current under specified thermal conditions (TA ≤ +85°C, proper PCB layout with exposed pad soldered to PGND). This rating assumes adequate input capacitance, appropriate inductor selection (e.g., 1µH, 6.9A peak), and ceramic output capacitors. Derating applies above +70°C ambient per the 23.8mW/°C thermal derating curve.
How does the MAX1945REUI+ achieve ±4% voltage margining, and what control signals are required?
The MAX1945REUI+ achieves ±4% voltage margining using dedicated CTL1 and CTL2 pins. With both pins at VCC, output is nominal; CTL1=VCC/CTL2=GND sets –4%; CTL1=GND/CTL2=VCC sets +4%; both at GND disables the regulator. This function is exclusive to the MAX1945R variant and relies on internal reference scaling-not external resistors-ensuring accuracy across temperature and load.
Can the MAX1945REUI+ operate with an input voltage below 2.6V, and if so, under what conditions?
Yes-the MAX1945REUI+ can operate with input as low as 2.25V when VCC is supplied at 3.3V or 5V (per General Description). This extended low-VIN capability enables use with partially discharged batteries or low-dropout pre-regulators, but requires external VCC biasing (via 10Ω resistor from IN) and careful attention to UVLO thresholds (2.20V–2.35V falling/rising).
What is the purpose of the SYNCOUT pin on the MAX1945REUI+, and how is it used in multi-phase designs?
The SYNCOUT pin on the MAX1945REUI+ provides a clock signal 180° out-of-phase with the internal switching frequency. When paired with a second MAX1945REUI+ or MAX1945SEUI+, this enables interleaved two-phase operation-halving input ripple current, reducing required input capacitance, and improving thermal distribution across both regulators without external phase-shift circuitry.
Does the MAX1945REUI+ require external compensation components, and where are they connected?
Yes-the MAX1945REUI+ requires external compensation components connected to the COMP pin (Pin 14). A series RC network (e.g., 2.2kΩ + 1nF) from COMP to GND sets loop bandwidth and phase margin. The COMP node is actively driven during regulation but pulled to GND during shutdown, ensuring predictable startup and fault recovery behavior.
MAX1945REUI+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- 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
MAX1945REUI+ FAQ
1.How can I place an order for MAX1945REUI+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1945REUI+ 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 MAX1945REUI+ reliable?
The price and inventory of MAX1945REUI+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1945REUI+ is usually 5 days.
3.What payment methods are accepted for MAX1945REUI+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1945REUI+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1945REUI+?
MAX1945REUI+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1945REUI+ 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 MAX1945REUI+?
For technical support, including MAX1945REUI+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1945REUI+ requirements.
6.How does Aetrix verify that MAX1945REUI+ is sourced from the original manufacturer or authorized distributors?
All MAX1945REUI+ 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 MAX1945REUI+ meets industry standards.
7.What is the process for return or replacement of MAX1945REUI+?
All MAX1945REUI+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX1945REUI+, 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 MAX1945REUI+ part is unused and in its original packaging.
Return procedure for MAX1945REUI+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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