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Analog Devices Inc./Maxim Integrated MAX1921EUT18
- Part No.:
- MAX1921EUT18
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- SOT-23-6
- Datasheet:
-
MAX1921EUT18.pdf
- Description:
- IC REG BUCK 1.8V 400MA SOT23-6
- Quantity:
- Payment:
- Shipping:
Inventory:11,179
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Product details
Overview
MAX1921EUT18 from Maxim Integrated is a fixed-output, 1.8V, 400mA synchronous step-down DC-DC converter in a 6-pin SOT23 package. It operates from a 2V to 5.5V input, delivers ±1.5% initial output accuracy, maintains 50µA quiescent current, and switches up to 1.2MHz for compact external components. It is used in battery-powered handheld devices requiring efficient low-voltage rail generation.
For engineers reviewing the MAX1921EUT18 datasheet, MAX1921EUT18 pinout, MAX1921EUT18 application, or MAX1921EUT18 equivalent, key selection criteria include its factory-set 1.8V output, SOT23-6 footprint, internal synchronous rectification, shutdown current of 0.1µA, and compatibility with ceramic output capacitors in voltage-positioning topologies.
Technical Context
The MAX1921EUT18 employs a proprietary current-limited control scheme with 400ns minimum on/off times, enabling high efficiency across light-to-heavy loads while maintaining fast transient response. Its internal synchronous rectifier eliminates the need for an external Schottky diode and reduces conduction losses.
It uses voltage positioning feedback via the OUT pin (not FB), where regulation is achieved through an internal resistive divider set for 1.8V. Startup occurs at 2.0V input, with UVLO hysteresis of 200mV, and soft-start limits inrush current by ramping the current limit in 25% steps.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 1.8V ±1.5% initial accuracy; no external resistor required. |
| Input Voltage Range | 2.0V to 5.5V; enables direct Li+ or dual-AA operation without pre-regulation. |
| Max Output Current | 400mA guaranteed; supports core logic rails in portable SoC applications. |
| Quiescent Current | 50µA at no load; extends battery life in always-on subsystems. |
| Shutdown Current | 0.1µA; suitable for deep-sleep power domains in wireless handsets. |
| Switching Frequency | Up to 1.2MHz; allows use of ≤10µH inductors and 4.7–10µF ceramic output capacitors. |
| Package | SOT23-6 (U6S-3); 2.9mm × 2.9mm × 1.45mm footprint compatible with standard pick-and-place. |
Pinout & Package
MAX1921EUT18 is housed in a 6-pin SOT23-6 package (JEDEC MO-178AA, pkg code U6S-3), with exposed pad not electrically connected. Pin 1 is marked by a dot or beveled edge; lead-free variants use "+" suffix and omit the pin 1 indicator.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (IN) | Power input | Accepts 2V–5.5V; requires local 2.2µF ceramic bypass capacitor. |
| 2 (AGND) | Analog ground reference | Must be tied directly to PGND at a single star point to minimize noise coupling into feedback path. |
| 3 (SHDN) | Active-low enable | Pull to GND for 0.1µA shutdown; tie to IN for normal operation; VIH ≥1.6V, VIL ≤0.4V. |
| 4 (LX) | Switch node | Connects to inductor; high dv/dt node-must be routed short and away from sensitive analog traces. |
| 5 (PGND) | Power ground return | Carries high pulsed currents; connect to AGND only at single-point star ground near device. |
| 6 (OUT) | Fixed-output voltage sense | Internally connected to 1.8V divider; no external feedback-output voltage is factory-trimmed and non-adjustable. |
Key Features
| Feature | Design Value |
|---|---|
| Internal synchronous rectification | Eliminates external Schottky diode, improving efficiency >90% and reducing thermal stress in space-constrained layouts. |
| Digital soft-start | Ramps current limit in 25% increments, limiting inrush and relaxing input capacitor sizing requirements for alkaline/Li+ sources. |
| Voltage positioning topology | Uses LX feed-forward and R1/CFF compensation to halve peak-to-peak output excursions during load transients vs. conventional buck regulators. |
| High-frequency operation | 1.2MHz max switching enables <10µH inductors and small ceramic output caps-reducing BOM cost and PCB area by >40% vs. 500kHz alternatives. |
| Low dropout behavior | Maintains regulation down to VIN = VOUT + 0.2V at light loads, supporting ultra-low headroom applications like 1.8V LDO replacement. |
Applications
| Wireless Handset Core Rail | PDAs and Palmtop Memory Supply |
|---|---|
Use Scenario: Powers ARM-based application processors and LPDDR memory in sub-100mm form factor handsets running on single-cell Li+. IC Role / Device Role / Timing Role: Primary 1.8V buck regulator delivering up to 400mA with <10mV load-step ripple under 200mA/µs transients. Use Value: Enables voltage positioning to suppress undershoot below 1.71V during CPU burst mode, avoiding memory timing violations. | Use Scenario: Supplies 1.8V to NAND flash and SRAM in industrial PDAs operating from dual AA batteries (2.4V–3.2V). IC Role / Device Role / Timing Role: High-efficiency step-down converter with 2.0V startup and 50µA quiescent current for extended standby life. Use Value: Delivers >88% efficiency at 100mA from 2.4V input, extending battery runtime by 3.2 hours per charge vs. linear regulator alternative. |
| CDMA Power Amplifier Bias | Portable Medical Sensor Node |
Use Scenario: Provides clean, low-noise 1.8V bias to CDMA PA driver stages in handset front-end modules. IC Role / Device Role / Timing Role: Fixed-output buck with internal soft-start and 0.1µA shutdown to coordinate PA enable sequencing. Use Value: Reduces supply-induced AM-to-PM distortion by limiting startup dI/dt and maintaining <2mV RMS output noise at 100kHz–10MHz. | Use Scenario: Powers ultra-low-power microcontroller and analog sensor interface in disposable wearable ECG patches. IC Role / Device Role / Timing Role: Primary system regulator operating from coin-cell (3V) with 0.1µA shutdown and 50µA quiescent draw. Use Value: Achieves 12-month shelf life and >6 months continuous operation by minimizing no-load consumption and enabling precise sleep-state entry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS62231DRVR | 1.8V fixed, 400mA, 2.05–6.5V input, 3MHz switching, 17µA IQ, WSON-6 (2×2mm) | Higher frequency enables smaller inductors but requires tighter layout control; lower IQ benefits long-term battery apps. | Select when board space is critical and input voltage may exceed 5.5V; verify EMI filtering for 3MHz harmonics. |
| RT8059GJ6 | 1.8V fixed, 500mA, 2.5–5.5V input, 1.5MHz switching, 25µA IQ, SOT23-6 | Wider current capability and lower IQ, but requires ≥2.5V VIN-unsuitable for 2.0V Li+ start-up. | Select for higher load margin or lower quiescent needs; avoid if system must start from 2.0V or below. |
Compared with MAX1921EUT18, TPS62231DRVR offers smaller solution size and lower IQ but lacks 2.0V startup capability; RT8059GJ6 provides higher output current and lower IQ but cannot operate below 2.5V input-making MAX1921EUT18 uniquely suited for 2.0V–5.5V battery rails with strict 1.8V accuracy and proven voltage positioning performance.
Availability
MAX1921EUT18 is available at Aetrix Electronics and suitable for wireless handsets, portable medical sensors, PDAs, and CDMA power amplifier supplies requiring stable component supply, RoHS-compliant sourcing, and long-term production continuity.
Supply support for MAX1921EUT18 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 space-constrained, battery-powered portable electronics needing high-efficiency, low-noise, fixed-output DC-DC conversion in minimal footprint.
FAQ
What is the output voltage tolerance of the MAX1921EUT18 over temperature and load?
The MAX1921EUT18 guarantees ±3% output voltage accuracy over the full -40°C to +85°C operating temperature range and 0–400mA load current. At room temperature and zero load, initial accuracy is tighter at ±1.5%. This is achieved via factory laser trimming of the internal feedback divider network specific to the MAX1921EUT18 variant.
Can the MAX1921EUT18 be used with a tantalum output capacitor?
Yes, the MAX1921EUT18 supports tantalum output capacitors using the application circuit in Figure 3 of the datasheet. Stability requires sufficient ESR-typically ~25mV ripple at the internal feedback node-so select a tantalum capacitor with typical ESR ≈ 2× the calculated minimum. Ceramic capacitors are preferred for better transient response and reliability.
Does the MAX1921EUT18 require an external feedback resistor network?
No. The MAX1921EUT18 has a factory-preset 1.8V output and uses the OUT pin connected to an internal voltage divider. Unlike the adjustable MAX1920, it does not use the FB pin and requires no external resistors-simplifying layout and eliminating resistor tolerance errors in the output voltage.
What is the minimum input voltage required for the MAX1921EUT18 to start switching?
The MAX1921EUT18 starts switching when the input voltage rises to 2.0V (typical startup voltage). Its UVLO threshold is 1.85V (rising) with 200mV hysteresis, ensuring reliable turn-on from single-cell Li+ or two alkaline cells without brown-out oscillation.
How does the voltage positioning architecture of the MAX1921EUT18 improve load transient response?
The MAX1921EUT18's voltage positioning uses feed-forward from the LX node and CFF compensation to intentionally introduce controlled load regulation (~15mΩ effective resistance). This reduces output voltage undershoot/overshoot during fast load steps by half compared to traditional buck regulators-critical for powering noise-sensitive RF and memory circuits.
MAX1921EUT18 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 FAQ
1.How can I place an order for MAX1921EUT18 through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1921EUT18 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 reliable?
The price and inventory of MAX1921EUT18 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1921EUT18 is usually 5 days.
3.What payment methods are accepted for MAX1921EUT18?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1921EUT18 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1921EUT18?
MAX1921EUT18 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1921EUT18 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?
For technical support, including MAX1921EUT18 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1921EUT18 requirements.
6.How does Aetrix verify that MAX1921EUT18 is sourced from the original manufacturer or authorized distributors?
All MAX1921EUT18 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 meets industry standards.
7.What is the process for return or replacement of MAX1921EUT18?
All MAX1921EUT18 units undergo pre-shipment inspection (PSI). If there is an issue with MAX1921EUT18, 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 part is unused and in its original packaging.
Return procedure for MAX1921EUT18:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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