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Analog Devices Inc./Maxim Integrated MAX1921EUT18+T
- Part No.:
- MAX1921EUT18+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- SOT-23-6
- Datasheet:
-
MAX1921EUT18+T.pdf
- Description:
- IC REG BUCK 1.8V 400MA SOT6
- Quantity:
- Payment:
- Shipping:
Inventory:2,361
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Product details
Overview
The MAX1921EUT18+T from Maxim Integrated is a fixed-output 1.8V, 400mA synchronous step-down DC-DC converter in a 6-pin SOT23 package, featuring 50μA quiescent current, 1.2MHz max switching frequency, ±1.5% initial output accuracy, and internal soft-start-designed for space-constrained battery-powered equipment such as CDMA power amplifier supplies.
For engineers reviewing the MAX1921EUT18+T datasheet, MAX1921EUT18+T pinout, MAX1921EUT18+T application, or MAX1921EUT18+T equivalent, key selection considerations include guaranteed 400mA output at 1.8V, shutdown current of 0.1μA, input voltage range of 2V to 5.5V, and compatibility with ceramic output capacitors using voltage-positioning topology.
Technical Context
The MAX1921EUT18+T employs a proprietary current-limited control scheme with 400ns minimum on-time and off-time, enabling fast transient response and stable operation across light-to-heavy loads without external compensation. Its internal synchronous rectifier eliminates the need for an external Schottky diode.
This device integrates factory-trimmed 1.8V feedback, UVLO with 1.95V rising threshold and 200mV hysteresis, and logic-controlled active-low shutdown that places LX in high-impedance state while reducing supply current to 0.1μA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 1.8V ±1.5% (initial), supports stable regulation for low-voltage digital core rails |
| Max Output Current | 400mA continuous-sufficient for RF power amplifiers and microcontroller I/O domains |
| Input Voltage Range | 2.0V to 5.5V-enables direct operation from single Li+ cells or 3.3V/5V system rails |
| Quiescent Current | 50μA-minimizes standby power loss in always-on portable systems |
| Shutdown Current | 0.1μA-extends battery life during deep-sleep modes |
| Switching Frequency | Up to 1.2MHz-permits use of compact 4.7µH inductors and 4.7µF ceramic output capacitors |
| UVLO Threshold | 1.95V (rising), 1.65V (falling)-prevents erratic startup/shutdown near battery depletion |
Pinout & Package
Package: 6-pin SOT23-6, lead-free (RoHS-compliant), footprint compatible with standard SOT23 land patterns.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - IN | Power input | Accepts 2V–5.5V; requires local 2.2µF ceramic bypass capacitor to PGND |
| 2 - AGND | Analog ground reference | Must be connected to PGND at a single-point star ground to minimize noise coupling into FB/OUT |
| 3 - SHDN | Active-low enable control | Pull to GND for 0.1μA shutdown; tie to IN for normal operation |
| 4 - OUT | Fixed-output voltage sense | Internally connected to precision 1.8V divider; no external resistor network required |
| 5 - PGND | Power ground return | Carries high-frequency inductor current; connect directly to AGND at package edge |
| 6 - LX | Switch node | Drives external inductor; requires short, low-inductance trace to minimize EMI and ringing |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous rectification | Eliminates external Schottky diode, improving efficiency >90% and reducing thermal load |
| Internal digital soft-start | Gradually ramps current limit in 25% steps, limiting inrush and relaxing input capacitor sizing |
| Voltage positioning topology | Leverages inductor DCR for feed-forward load transient response-reduces output overshoot/undershoot by ~50% |
| High-frequency operation | 1.2MHz max switching enables small 4.7µH inductors and 4.7µF ceramic output caps-reducing board area by >40% vs. 500kHz converters |
| Low-noise shutdown mode | 0.1μA shutdown current with high-impedance LX ensures zero load on battery during sleep |
Applications
| CDMA Power Amplifier Supply | Li+ Battery-Powered Handhelds |
|---|---|
Use Scenario: Powers Class AB/ABM RF power amplifier stages requiring tightly regulated 1.8V at up to 400mA peak current. IC Role / Device Role / Timing Role: Primary buck regulator delivering clean, low-noise 1.8V rail with fast line/load transient response to maintain PA linearity. Use Value: Internal voltage positioning reduces output voltage excursions by ~50% during PA burst-mode transients, preserving EVM and ACLR performance. | Use Scenario: Supplies 1.8V logic rails for baseband processors and interface ICs in slim-profile wireless handsets operating from single-cell Li+ batteries. IC Role / Device Role / Timing Role: High-efficiency step-down converter maintaining regulation down to 2.0V input-extending usable battery range. Use Value: 50μA quiescent current and 0.1μA shutdown current maximize standby time between user interactions. |
| PDA/Palmtop Core Logic | Portable Medical Sensors |
Use Scenario: Generates 1.8V supply for ARM-based application processors and memory interfaces in handheld computing devices. IC Role / Device Role / Timing Role: Compact, integrated buck converter replacing linear regulators to reduce heat and extend runtime. Use Value: 6-pin SOT23 package and 1.2MHz operation allow full solution size under 15mm²-critical for thin form factors. | Use Scenario: Powers ultra-low-power sensor signal chains (e.g., ADCs, op-amps, BLE radios) in wearable diagnostic monitors. IC Role / Device Role / Timing Role: Efficient, low-noise DC-DC source supporting intermittent wake-up cycles with sub-μA sleep current. Use Value: Factory-trimmed 1.8V output eliminates calibration overhead; ±1.5% accuracy ensures consistent analog front-end biasing. |
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 | 1.8V fixed, 400mA, 2.05V–6.5V input, 3.6MHz switching, 17μA IQ | Higher frequency allows smaller passives but increases EMI sensitivity; lower IQ benefits long-duration sleep | Prefer for designs prioritizing minimal solution size and lowest quiescent current over cost and layout simplicity |
| RT8059GJ6 | 1.8V fixed, 500mA, 2.5V–5.5V input, 1.5MHz switching, 60μA IQ | Higher current rating and wider VIN range; slightly higher IQ and different pinout (SHDN on Pin 5) | Choose when margin beyond 400mA is needed or when sourcing from Richtek's distribution channels |
Compared with TPS62231DRYR and RT8059GJ6, the MAX1921EUT18+T offers superior voltage positioning for load transients, proven stability with 4.7µF ceramic outputs, and industry-standard SOT23 pin compatibility-making it optimal for cost-sensitive, space-constrained portable designs where transient robustness is critical.
Availability
The MAX1921EUT18+T is available at Aetrix Electronics and suitable for CDMA power amplifier supplies, Li+ battery-powered handhelds, and portable medical sensors requiring stable component supply with full RoHS compliance and traceable lot history.
Supply support for MAX1921EUT18+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
Maxim Integrated (now part of Analog Devices) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and consumer applications.
The MAX1920/MAX1921 product line was designed specifically for ultra-compact, high-efficiency DC-DC conversion in battery-powered portable electronics-emphasizing low quiescent current, internal soft-start, and voltage positioning for demanding RF and processor supply rails.
FAQ
What is the exact output voltage tolerance of the MAX1921EUT18+T over temperature and load?
The MAX1921EUT18+T delivers 1.8V output with ±1.5% initial accuracy at +25°C and ±3% over the full -40°C to +85°C temperature range and 0–400mA load. This specification is guaranteed by design and confirmed in the Electrical Characteristics table of the official datasheet. The MAX1921EUT18+T achieves this via factory laser-trimming of its internal feedback divider, eliminating external resistor tolerances.
Does the MAX1921EUT18+T require an external feedback resistor network?
No, the MAX1921EUT18+T does not require external feedback resistors. It features a factory-preset 1.8V output implemented via an internal precision voltage divider connected to the OUT pin. Unlike the adjustable MAX1920, the MAX1921EUT18+T uses dedicated OUT pin functionality-simplifying layout and reducing BOM count. This is explicitly stated in the Pin Description and Selector Guide sections of the MAX1921EUT18+T datasheet.
What is the recommended inductor value for the MAX1921EUT18+T in a typical 3.3V-input, 1.8V-output application?
For a 3.3V input and 1.8V output, the MAX1921EUT18+T datasheet recommends a 4.7µH inductor rated for ≥550mA saturation current (e.g., Coilcraft LPO1704 or Sumida CDRH2D18). This value balances efficiency, transient response, and physical size-validated in Table 1 and Figure 1. Using this inductor with a 4.7µF ceramic output capacitor and 3300pF feed-forward capacitor achieves stable voltage-positioning operation per the design procedure.
Can the MAX1921EUT18+T operate from a 2.0V input supply?
Yes, the MAX1921EUT18+T supports input voltages as low as 2.0V-specifically enabled for the 1.5V, 1.8V, 2.5V, 3.0V, and 3.3V output variants per the Electrical Characteristics table. At 2.0V input, it maintains regulation for 1.8V output up to 200mA (as specified in the Startup Voltage row). This capability is essential for extending runtime in single-cell Li+ applications nearing end-of-discharge.
How does the MAX1921EUT18+T implement soft-start, and what is its duration?
The MAX1921EUT18+T implements internal digital soft-start by initializing the current limit at 25% of full scale and incrementing it in four 25% steps until reaching 100%. This staged ramp limits inrush current and reduces input capacitor stress. While the exact time depends on load and input conditions, typical startup to full regulation occurs within 1–2ms, as shown in the Soft-Start and Shutdown Response plot (MAX1920 toc12) in the datasheet. The MAX1921EUT18+T shares this behavior with the MAX1920 family.
MAX1921EUT18+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- SOT-23-6
- Packaging:
- Tape & Reel (TR)
- 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):
- 1.8V
- 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-6
MAX1921EUT18+T FAQ
1.How can I place an order for MAX1921EUT18+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1921EUT18+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 MAX1921EUT18+T reliable?
The price and inventory of MAX1921EUT18+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1921EUT18+T is usually 5 days.
3.What payment methods are accepted for MAX1921EUT18+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1921EUT18+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1921EUT18+T?
MAX1921EUT18+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1921EUT18+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 MAX1921EUT18+T?
For technical support, including MAX1921EUT18+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1921EUT18+T requirements.
6.How does Aetrix verify that MAX1921EUT18+T is sourced from the original manufacturer or authorized distributors?
All MAX1921EUT18+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 MAX1921EUT18+T meets industry standards.
7.What is the process for return or replacement of MAX1921EUT18+T?
All MAX1921EUT18+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX1921EUT18+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 MAX1921EUT18+T part is unused and in its original packaging.
Return procedure for MAX1921EUT18+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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