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Analog Devices Inc./Maxim Integrated MAX1921EUT25
- Part No.:
- MAX1921EUT25
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- SOT-23-6
- Datasheet:
-
MAX1921EUT25.pdf
- Description:
- IC REG BUCK 2.5V 400MA SOT23-6
- Quantity:
- Payment:
- Shipping:
Inventory:870
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Product details
Overview
MAX1921EUT25 from Maxim Integrated is a fixed-output 2.5V, 400mA synchronous step-down DC-DC converter in a 6-pin SOT23 package. It operates from 2V to 5.5V input, delivers ±3% output voltage accuracy over temperature and load, maintains 50µA quiescent current, and uses a proprietary current-limited control scheme for >90% efficiency in space-constrained battery-powered systems.
For engineers reviewing the MAX1921EUT25 datasheet, MAX1921EUT25 pinout, MAX1921EUT25 application, or MAX1921EUT25 equivalent, key selection criteria include its factory-set 2.5V output, 1.2MHz max switching frequency enabling compact external components, internal soft-start limiting inrush current, logic-controlled shutdown (0.1µA), and compatibility with ceramic or tantalum output capacitors in voltage-positioning topologies.
Technical Context
The MAX1921EUT25 implements a proprietary current-limited control architecture with 400ns minimum on-time and off-time, enabling fast transient response and stable operation across 0–400mA load range. Its internal synchronous rectifier eliminates the need for an external Schottky diode while maintaining high efficiency at light loads via pulse-skipping behavior.
This device integrates analog ground (AGND) and power ground (PGND) separation, supports voltage positioning for reduced load-transient overshoot/undershoot, and features built-in UVLO (1.85V rising, 1.50V falling) with 200mV hysteresis to ensure reliable startup under weak input sources like alkaline or Li+ cells.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 2.5V ±3% over -40°C to +85°C and 0–400mA load - ensures stable core supply for low-voltage logic without external feedback resistors. |
| Input Voltage Range | 2.0V to 5.5V - supports single-cell Li+, dual-cell alkaline, or regulated 3.3V/5V rails without external LDO pre-regulation. |
| Max Output Current | 400mA - sufficient for powering baseband processors, RF front-end ICs, or sensor subsystems in portable electronics. |
| Quiescent Current | 50µA - enables multi-day standby in always-on battery applications such as handheld terminals or IoT edge nodes. |
| Switching Frequency | Up to 1.2MHz - permits use of small 4.7µH–10µH inductors and 4.7µF–10µF ceramic output capacitors, reducing board area by >40% vs. lower-frequency converters. |
| Shutdown Current | 0.1µA - allows deep-sleep modes in wireless handsets and PDAs without significant battery drain during inactive periods. |
| UVLO Threshold | 1.85V (rising), 1.50V (falling) - prevents erratic operation during brown-out conditions and supports graceful shutdown before battery depletion. |
Pinout & Package
MAX1921EUT25 is housed in a 6-pin SOT23-6 package (JEDEC MO-178AA, footprint U6S-3*), measuring 2.9mm × 2.8mm × 1.3mm with gull-wing leads. The exposed pad variant is not used for this part; thermal dissipation relies on PCB copper area connected to PGND.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 IN | Power Input | Accepts 2.0V–5.5V supply; requires local 2.2µF ceramic bypass capacitor to minimize input ripple and EMI. |
| 2 AGND | Analog Ground Reference | Must be connected to PGND at a single-point star ground to avoid noise coupling into feedback path. |
| 3 SHDN | Active-Low Enable | Pulled high to IN for operation; driven low to GND for 0.1µA shutdown - compatible with standard GPIOs. |
| 4 LX | Switch Node | Connects to inductor; carries high dv/dt switching waveform - must be routed short and away from sensitive analog traces. |
| 5 PGND | Power Ground Return | Carries high pulsed currents from LX and output capacitor; connects to AGND only at one point near the IC. |
| 6 OUT | Fixed-Voltage Sense | Internally connected to factory-trimmed resistor divider for 2.5V regulation - no external feedback required. |
Key Features
| Feature | Design Value |
|---|---|
| Internal Synchronous Rectification | Eliminates external Schottky diode, reduces conduction losses, and improves full-load efficiency to >90% without thermal derating. |
| Digital Soft-Start | Gradually ramps current limit from 25% to 100% in steps, limiting inrush current and relaxing input capacitor sizing requirements. |
| Voltage Positioning Architecture | Leverages inductor DCR for intentional load regulation, cutting peak-to-peak output voltage excursions by ~50% during load transients. |
| High-Frequency Operation (up to 1.2MHz) | Enables use of miniature 0805/1206 inductors and low-ESR ceramic capacitors, reducing total solution size to <25mm². |
| Separate AGND and PGND Pins | Minimizes ground bounce and noise injection into feedback circuitry, improving regulation accuracy and stability margin. |
Applications
| CDMA Power Amplifier Supply | Battery-Powered Handheld Terminals |
|---|---|
Use Scenario: Powers CDMA PA stages requiring clean, stable 2.5V rail with fast transient response to handle burst-mode transmission. IC Role / Device Role / Timing Role: Primary buck regulator delivering regulated 2.5V at up to 400mA with <10µs recovery from 200mA→400mA load steps. Use Value: Voltage positioning reduces output overshoot/undershoot by half versus conventional buck controllers, preventing PA distortion or shutdown during RF bursts. | Use Scenario: Supplies main processor and peripheral ICs in ruggedized industrial handhelds operating from dual AA or Li+ batteries. IC Role / Device Role / Timing Role: High-efficiency step-down converter enabling >72-hour runtime in active mode and multi-week standby via 50µA IQ and 0.1µA shutdown. Use Value: 2V min input supports operation down to end-of-life battery voltage, extending usable battery life without requiring cell replacement or boost conversion. |
| PDAs and Palmtop Systems | Low-Voltage Microcontroller Core Supply |
Use Scenario: Provides 2.5V VDD_IO or auxiliary rail for memory interfaces and display drivers in legacy PDA platforms. IC Role / Device Role / Timing Role: Compact SOT23-6 DC-DC converter replacing linear regulators to eliminate thermal bottlenecks in dense PCB layouts. Use Value: >90% efficiency at 300mA reduces power dissipation by >75% vs. LDO, allowing fanless operation and higher component density. | Use Scenario: Generates precise 2.5V core voltage for ARM Cortex-M or RISC-V microcontrollers with tight analog reference requirements. IC Role / Device Role / Timing Role: Fixed-output buck regulator with ±3% accuracy and low output ripple (<15mV pk-pk) meeting MCU ADC and PLL supply specs. Use Value: Factory-trimmed internal feedback eliminates resistor tolerance errors and layout sensitivity, ensuring consistent performance across production batches. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS62231DRYR | Fixed 2.5V output, 400mA, 2.05V–6.5V input, 1.8MHz switching, 22µA IQ - higher frequency but lower max input voltage margin. | Requires smaller inductor (2.2µH) but less tolerant of input transients above 6.5V; lacks voltage positioning architecture. | Select when board space is critical and input rail is tightly regulated; avoid if using unregulated alkaline or Li+ sources with potential overvoltage. |
| RT8059GJ6 | Fixed 2.5V output, 500mA, 2.5V–5.5V input, 1.5MHz switching, 30µA IQ - wider output current headroom but narrower input range. | Cannot operate below 2.5V input, excluding single-cell alkaline use; no soft-start or UVLO hysteresis specification provided. | Prefer for higher-current loads where 2.5V–5.5V input is guaranteed; verify startup reliability with marginal batteries before deployment. |
Compared with TPS62231DRYR and RT8059GJ6, MAX1921EUT25 offers superior input voltage flexibility (2.0V min), integrated voltage positioning for robust transient response, and proven soft-start behavior with weak-source batteries - making it optimal for cost-sensitive, battery-first designs where reliability trumps raw frequency or current headroom.
Availability
MAX1921EUT25 is available at Aetrix Electronics and suitable for CDMA power amplifier supplies, battery-powered handheld terminals, and low-voltage microcontroller core supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.
Supply support for MAX1921EUT25 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, automotive, and communications applications.
The MAX1920/MAX1921 product line was engineered specifically for ultra-compact, high-efficiency DC-DC conversion in portable battery-powered equipment where board area, thermal performance, and light-load efficiency are critical constraints.
FAQ
What is the output voltage tolerance of the MAX1921EUT25 over temperature and load?
The MAX1921EUT25 guarantees ±3% output voltage accuracy across the full operating temperature range (-40°C to +85°C) and load current range (0 to 400mA). This specification is confirmed in the Electrical Characteristics table under "Output Voltage Accuracy (MAX1921)" with VIN = 3.6V and TA = -40°C to +85°C. At 25°C and zero load, initial accuracy is tighter at ±1.5%.
Can the MAX1921EUT25 operate from a single alkaline cell?
Yes, the MAX1921EUT25 can operate from a single alkaline cell. Its 2.0V minimum input voltage and 1.50V UVLO falling threshold allow functional operation down to approximately 1.6V under light load, covering the full discharge curve of a fresh alkaline cell (1.5V nominal, ~0.9V end-of-life). Startup is ensured above 1.85V.
Does the MAX1921EUT25 require external feedback resistors to set the output voltage?
No, the MAX1921EUT25 does not require external feedback resistors. As a factory-preset variant, it uses an internal trimmed resistor divider connected to the OUT pin to deliver a fixed 2.5V output. This eliminates component count, layout sensitivity, and resistor tolerance errors - unlike the adjustable MAX1920 which requires FB pin connection to an external divider.
What is the purpose of separate AGND and PGND pins on the MAX1921EUT25?
The separate AGND and PGND pins on the MAX1921EUT25 isolate analog reference circuitry from high-current power return paths. AGND serves as the quiet ground reference for internal error amplifiers and comparators, while PGND carries pulsed inductor current. Connecting them at a single star point near the IC prevents ground bounce from modulating regulation accuracy - a critical design requirement for stable 2.5V output under dynamic load.
How does the MAX1921EUT25 achieve high efficiency at light loads?
The MAX1921EUT25 achieves high light-load efficiency through its proprietary current-limited control scheme with 400ns minimum on-time. At low output currents, the controller reduces peak inductor current by terminating each switching cycle after the minimum on-time, effectively entering pulse-skipping mode. This minimizes switching losses and maintains >85% efficiency even at 1mA load, as verified in Typical Operating Characteristics graphs.
MAX1921EUT25 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- SOT-23-6
- Packaging:
- Bulk
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 2.5V
- Voltage - Output (Max):
- -
- Current - Output:
- 400mA
- Frequency - Switching:
- Up to 1.2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-6
MAX1921EUT25 FAQ
1.How can I place an order for MAX1921EUT25 through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1921EUT25 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 MAX1921EUT25 reliable?
The price and inventory of MAX1921EUT25 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1921EUT25 is usually 5 days.
3.What payment methods are accepted for MAX1921EUT25?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1921EUT25 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1921EUT25?
MAX1921EUT25 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1921EUT25 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 MAX1921EUT25?
For technical support, including MAX1921EUT25 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1921EUT25 requirements.
6.How does Aetrix verify that MAX1921EUT25 is sourced from the original manufacturer or authorized distributors?
All MAX1921EUT25 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 MAX1921EUT25 meets industry standards.
7.What is the process for return or replacement of MAX1921EUT25?
All MAX1921EUT25 units undergo pre-shipment inspection (PSI). If there is an issue with MAX1921EUT25, 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 MAX1921EUT25 part is unused and in its original packaging.
Return procedure for MAX1921EUT25:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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