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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 SOT23-6
- Quantity:
- Payment:
- Shipping:
Inventory:7,500
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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 voltage accuracy, and internal soft-start - designed for space-constrained battery-powered equipment such as CDMA power amplifier supplies and handheld terminals.
For engineers reviewing the MAX1921EUT18-T datasheet, MAX1921EUT18-T pinout, MAX1921EUT18-T application, or MAX1921EUT18-T equivalent, key selection criteria include guaranteed 400mA output at 1.8V, shutdown current of 0.1μA, input range of 2V to 5.5V, SOT23-6 thermal performance (695mW at +70°C), and compatibility with ceramic output capacitors using voltage-positioning topology.
Technical Context
The MAX1921EUT18-T uses a proprietary current-limited control scheme 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 external Schottky diodes and supports >90% efficiency at medium loads.
It implements digital soft-start by ramping current limit in 25% steps, limiting inrush during startup. Shutdown mode disables all internal circuitry and sets LX to high impedance, reducing supply current to 0.1μA - critical for ultra-low-power portable systems requiring long standby life.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 1.8V ±1.5% (initial), ±3% over full temperature/load range - ensures stable core logic supply for low-voltage ASICs and RF ICs. |
| Max Output Current | 400mA continuous - sufficient to power CDMA PA stages or baseband processors without external current boosting. |
| Input Voltage Range | 2.0V to 5.5V - supports single-cell Li+ (2.7–4.2V), alkaline (2×AA = ~3V), and USB-powered (5V) configurations. |
| Quiescent Current | 50μA (no load, active) - enables multi-week battery life in always-on sensor nodes or standby circuits. |
| Shutdown Current | 0.1μA - reduces system leakage during deep sleep, critical for energy-harvesting and IoT edge devices. |
| Switching Frequency | Up to 1.2MHz - allows use of compact 4.7μH inductors and 4.7μF ceramic output capacitors, minimizing PCB area. |
| UVLO Threshold | 1.85V (rising), 1.50V (falling) with 200mV hysteresis - prevents erratic startup/shutdown near battery depletion. |
Pinout & Package
Package: 6-pin SOT23-6 (JEDEC MO-178AA), 2.9mm × 1.6mm footprint, 1.1mm height, lead-free (RoHS-compliant).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - IN | Power input | Accepts 2.0–5.5V; requires local 2.2μF ceramic bypass capacitor to PGND for EMI suppression and transient current sourcing. |
| 2 - AGND | Analog ground reference | Must be connected directly to PGND at a single point to avoid ground bounce affecting regulation accuracy. |
| 3 - SHDN | Active-low enable control | Pulled high to IN for operation; driven low to enter 0.1μA shutdown - compatible with GPIOs of microcontrollers. |
| 4 - OUT | Fixed-voltage sense node | Internally connected to factory-trimmed resistor divider for 1.8V output; no external feedback components required. |
| 5 - PGND | Power ground return | Carries high-frequency inductor current; must be routed with low-inductance path to IN capacitor ground. |
| 6 - LX | Switch node | Connects to inductor; carries high dv/dt switching waveform - requires tight layout to minimize EMI and parasitic ringing. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous rectification | Eliminates external Schottky diode, improving efficiency by ≥5% vs. asynchronous designs and reducing thermal stress in SOT23. |
| Digital soft-start | Ramps current limit in four 25% steps, limiting peak input current to ≤1.5× rated output - avoids brownout in weak battery sources. |
| Voltage positioning topology | Uses inductor DCR sensing via R1/CFF network to provide intentional load regulation (~15mV/A), halving output voltage excursions during 20–320mA transients. |
| High-frequency operation | 1.2MHz max switching enables <10mm² total solution size with 4.7μH/4.7μF ceramic components - ideal for PDA and handset PCB real estate constraints. |
| Low-noise shutdown | 0.1μA shutdown current with high-impedance LX ensures zero reverse current into battery and no output droop during sleep. |
Applications
| CDMA Power Amplifier Supply | Handheld Terminal Core Logic |
|---|---|
Use Scenario: Powers Class AB CDMA PA stage requiring clean, stable 1.8V rail under dynamic 100–400mA load modulation. IC Role / Device Role / Timing Role: Primary DC-DC regulator delivering regulated 1.8V with <5mV ripple and <20μs transient recovery. Use Value: Enables >90% PA efficiency while maintaining adjacent-channel leakage ratio (ACLR) compliance via low-noise, fast-response regulation. | Use Scenario: Supplies 1.8V core voltage to ARM-based baseband processor in palm-sized wireless terminal operating from single Li+ cell. IC Role / Device Role / Timing Role: Main system PMIC buck converter supporting dynamic voltage scaling and deep-sleep modes. Use Value: 50μA quiescent current extends battery runtime to >120 hours in standby; 0.1μA shutdown enables firmware-controlled wake-up without auxiliary LDO. |
| Alkaline-Powered PDA | Low-Power Sensor Node |
Use Scenario: Regulates 1.8V for LCD controller and flash memory interface in 2×AA-powered PDA with variable 50–350mA load profile. IC Role / Device Role / Timing Role: High-efficiency step-down converter bridging 2.0–3.2V alkaline input to fixed 1.8V logic rail. Use Value: UVLO hysteresis (200mV) prevents oscillation near battery end-of-life; 1.2MHz operation minimizes inductor size for thin-profile design. | Use Scenario: Powers ultra-low-power MCU and BLE radio in coin-cell–operated environmental sensor with 10s active/3600s sleep duty cycle. IC Role / Device Role / Timing Role: Primary power converter activated only during measurement bursts, then held in shutdown. Use Value: 0.1μA shutdown current dominates system sleep budget, enabling >5-year battery life with CR2032. |
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, 3MHz switching, 22μA IQ, SOT23-6 - higher frequency but lower efficiency at light loads due to forced PWM. | Preferred for noise-sensitive RF sections where smaller LC filter is mandatory; less suitable for battery lifetime-critical sleep modes. | Select when board space is tighter than efficiency requirements, and input voltage stays >2.3V. |
| RT8059GJ6 | 1.8V fixed, 500mA, 1.5MHz, 35μA IQ, SOT23-6 - higher current rating and lower IQ, but no integrated soft-start and wider output tolerance (±2.5%). | Better for cost-sensitive industrial controllers needing margin above 400mA; lacks soft-start protection for high-impedance alkaline sources. | Choose when peak load exceeds 400mA or when 35μA IQ provides measurable runtime gain over 50μA. |
Compared with TPS62231DRYR and RT8059GJ6, the MAX1921EUT18-T offers superior light-load efficiency due to its proprietary current-limited control (not PWM/PFM hybrid), integrated soft-start for battery-friendly startup, and tighter ±1.5% initial accuracy - making it optimal for portable devices prioritizing battery longevity and reliable cold-start behavior.
Availability
MAX1921EUT18-T is available at Aetrix Electronics and suitable for CDMA power amplifier supplies, handheld terminal core logic, and alkaline-powered PDAs requiring stable component supply with consistent parametric performance across production lots.
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 engineered specifically for ultra-compact, high-efficiency DC-DC conversion in battery-powered handheld devices - emphasizing minimal external component count, low quiescent current, and robust transient response under varying input conditions.
FAQ
What is the exact output voltage tolerance of the MAX1921EUT18-T over temperature and load?
The MAX1921EUT18-T delivers 1.8V with ±1.5% initial accuracy at +25°C and no load. Over the full -40°C to +85°C temperature range and 0–400mA load, output voltage remains within ±3% of nominal - verified per Electrical Characteristics table, Note 1, and Typical Operating Characteristics plots for VOUT=1.8V.
Does the MAX1921EUT18-T require external feedback resistors?
No. The MAX1921EUT18-T has factory-preset 1.8V output implemented via internal trimmed resistor divider connected to the OUT pin. Unlike the adjustable MAX1920, it requires no external FB resistors - simplifying layout and eliminating resistor tolerance errors in the feedback path.
What is the recommended inductor value for the MAX1921EUT18-T in a typical 3.3V-input application?
For VIN=3.3V and VOUT=1.8V, Table 1 recommends a 4.7μH inductor with 4.7μF ceramic output capacitor and 4.75kΩ R1 feed-forward resistor. Coilcraft LPO1704 (4.7μH, 0.2Ω DCR, 1.1A Isat) is a validated option - ensuring no saturation at 400mA peak inductor current.
Can the MAX1921EUT18-T operate from a 2.0V input source?
Yes. The MAX1921EUT18-T supports VIN as low as 2.0V (per Absolute Maximum Ratings and Electrical Characteristics), enabling direct operation from two fresh alkaline cells (~3.0V) or deeply discharged Li+ cells (~2.5V). Startup occurs reliably above 2.0V due to 1.85V UVLO rising threshold.
How does the MAX1921EUT18-T achieve >90% efficiency without an external Schottky diode?
The MAX1921EUT18-T achieves >90% efficiency through internal synchronous rectification - integrating both high-side and low-side MOSFETs in a single SOT23-6 die. This eliminates forward voltage drop losses of external diodes and reduces conduction loss, especially at light-to-medium loads where diode Vf dominates inefficiency.
MAX1921EUT18-T 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):
- 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-23-6
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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