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Analog Devices Inc./Maxim Integrated MAX639ESA+
- Part No.:
- MAX639ESA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX639ESA+.pdf
- Description:
- IC REG BUCK ADJ/1.3V 225MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,631
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Product details
Overview
The MAX639ESA+ from Maxim Integrated is a 5V fixed-output, high-efficiency step-down DC-DC switching regulator with pulse-frequency-modulated (PFM) control, delivering up to 225mA output current, operating from 4V to 11.5V input, and consuming only 10µA quiescent current. It integrates a 1A internal PMOS power switch and features low-battery detection (LBI/LBO) for portable 9V-to-5V conversion in battery-powered instrumentation.
For engineers reviewing the MAX639ESA+ datasheet, MAX639ESA+ pinout, MAX639ESA+ application, or MAX639ESA+ equivalent, key selection criteria include its PFM efficiency profile across light-to-heavy loads, SO-8 package thermal performance, 5V preset output accuracy (±4% over temperature), and compatibility with standard 100µH inductors and Schottky diodes in minimal-component designs.
Technical Context
The MAX639ESA+ employs a variable-frequency, variable-duty-cycle PFM control scheme that maintains high efficiency (up to 91%) from 10µA to 225mA load by modulating switching frequency rather than pulse width. Its internal 1.28V bandgap reference feeds both the error comparator (for regulation) and the low-battery comparator (LBI threshold), enabling independent operation of LBO during shutdown.
Regulation is achieved via an internal voltage divider when VFB is grounded (5V output), or through external resistor feedback for adjustable outputs. The LX pin drives an external inductor with peak-current limiting governed by tON = 50µs × VIN/(VIN − VOUT) and tOFF ≥ 50µs × VIN/VOUT, ensuring constant IPEAK ≈ 50µs × VIN/L for stable operation across input voltage variations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 5.0V ±4% (guaranteed over −40°C to +85°C, 0–225mA load) |
| Input Voltage Range | 4.0V to 11.5V - supports 9V batteries and industrial 5V/12V rails |
| Quiescent Current | 10µA typical - enables >1-year battery life in always-on sensor nodes |
| Max Output Current | 225mA at VIN = 9V, L = 100µH - sufficient for microcontrollers and analog front-ends |
| Efficiency | 91% at 100mA (VIN = 9V) - exceeds linear regulators by >4× at medium loads |
| Low-Battery Threshold | 1.28V on LBI pin - configurable detection point for system brownout warning |
| Shutdown Threshold | 0.80V to 1.15V (SHDN pin) - robust noise margin for reliable enable/disable control |
Pinout & Package
MAX639ESA+ is housed in an 8-pin SO (Small Outline) package per JEDEC MS-012, with 1.27mm pitch, 4.9mm × 3.9mm body, and exposed pad not present. Thermal resistance θJA = 170°C/W (SO), derating 5.88mW/°C above +70°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT | Regulated output sense node | Internally connected to voltage divider; must be tied directly to output capacitor for stable 5V regulation |
| LBO | Open-drain low-battery output | Sinks up to 10mA when LBI < 1.28V; requires external pull-up for logic-level interface |
| LBI | Low-battery detector input | Compares external voltage (via R1/R2 divider) to 1.28V reference; active in shutdown |
| GND | Analog and power ground reference | Single ground connection point for feedback, LBO, and LX return - critical for ripple suppression |
| LX | PMOS switch drain terminal | Drives external inductor; peak current limited to 600mA; requires low-ESR catch diode |
| V+ | Positive supply input | Accepts 4–11.5V; must be decoupled with ≥33µF low-ESR capacitor near pin |
| VFB | Dual-mode feedback input | Grounded for 5V fixed output; connected to external divider for adjustable outputs (1.3V–VIN) |
| SHDN | Active-low shutdown control | Pulled below 0.8V disables LX; tied to V+ for always-on operation |
Key Features
| Feature | Design Value |
|---|---|
| Pulse-frequency-modulated (PFM) control | Enables 10µA quiescent current and >85% efficiency at 10µA load - ideal for intermittent-sensing applications |
| Integrated 1A PMOS power switch | Eliminates external FET and gate driver - reduces BOM count and layout area in space-constrained PCBs |
| Internal 1.28V precision reference | Feeds both regulation and low-battery comparators - ensures consistent trip points without external references |
| Low-battery detection with LBI/LBO pins | Provides system-level battery monitoring independent of main regulation loop - usable during shutdown |
| SO-8 package with industry-standard footprint | Enables drop-in replacement for legacy 5V buck regulators and simplifies thermal management vs. DIP |
Applications
| Portable Instrumentation | Handheld Terminals |
|---|---|
Use Scenario: Battery-powered multimeters and data loggers requiring stable 5V rail from 9V alkaline cells with multi-year shelf life. IC Role / Device Role / Timing Role: Primary 5V step-down regulator supplying MCU, ADC, and display backlight drivers. Use Value: 10µA quiescent current extends battery life beyond 2 years in sleep mode; PFM efficiency avoids thermal issues in sealed enclosures. | Use Scenario: Rugged handheld barcode scanners using AA/AAA batteries where cold-temperature startup and runtime are critical. IC Role / Device Role / Timing Role: Main 5V power source for ARM Cortex-M0 host, CMOS image sensor, and USB PHY. Use Value: LBI/LBO enables early battery warning before system reset; SO-8 package withstands mechanical shock and vibration. |
| 9V-to-5V Conversion | High-Efficiency Linear Regulator Replacement |
Use Scenario: Industrial sensor transmitters powered by 9V PP3 batteries needing regulated 5V for op-amps and 4–20mA DACs. IC Role / Device Role / Timing Role: Efficient DC-DC converter replacing obsolete 7805 linear regulators in legacy designs. Use Value: 91% efficiency at 100mA eliminates heatsink requirement and reduces board temperature rise by >15°C vs. linear solution. | Use Scenario: Low-power IoT edge nodes where 5V rail powers RF modules (e.g., ESP32) and sensors with burst transmission. IC Role / Device Role / Timing Role: High-efficiency alternative to LM78L05, reducing power loss during active transmit cycles. Use Value: Delivers 225mA at 9V input with <100mV output ripple - meets RF module supply noise requirements without additional filtering. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX640ESA+ | Fixed 3.3V output (not 5V); identical PFM architecture, SO-8 package, and 10µA IQ | Used where 3.3V logic/system rail required instead of 5V; same layout but different feedback configuration | Select MAX640ESA+ only if target system operates at 3.3V; not a pin-compatible 5V substitute |
| TPS62231DRVR | 3MHz PWM (not PFM); 2.05–6.0V input; 5V output; 22µA IQ; 300mA output; WSON-6 package | Higher switching frequency enables smaller inductors/caps; lacks integrated LBI/LBO comparator | Choose TPS62231DRVR for compact, high-frequency designs without battery monitoring; MAX639ESA+ preferred for ultra-low-IQ and built-in LBO |
Compared with MAX640ESA+, MAX639ESA+ provides 5V output essential for legacy 5V peripherals, while TPS62231DRVR offers higher frequency and smaller size but omits the low-battery detection function critical for battery-operated field instruments.
Availability
MAX639ESA+ is available at Aetrix Electronics and suitable for portable instrumentation, handheld terminals, and 9V-to-5V conversion applications requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.
Supply support for MAX639ESA+ 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, automotive, and communications markets.
The MAX639ESA+ belongs to Maxim's legacy high-efficiency, low-quiescent-current DC-DC converter family designed specifically for battery-powered portable equipment where extended runtime and simple bill-of-materials are primary design constraints.
FAQ
What is the guaranteed output voltage tolerance for MAX639ESA+ over temperature and load?
The MAX639ESA+ guarantees a 5.0V output with ±4% tolerance across the full operating temperature range (−40°C to +85°C) and load current (0–225mA), as confirmed by electrical characterization in the datasheet's "Electrical Characteristics" table under "Output Voltage (Note 2)" for MAX639.
Can MAX639ESA+ operate with input voltages below 4V?
No. The absolute minimum input voltage for MAX639ESA+ is 4.0V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 4V will result in dropout, unregulated output, or failure to start - it is not characterized or guaranteed for sub-4V operation.
Does MAX639ESA+ require an external diode, and what type is recommended?
Yes, MAX639ESA+ requires an external Schottky diode (e.g., 1N5817) connected between LX and VOUT. The datasheet specifies fast turn-on time and low forward voltage (<0.55V) to minimize losses; general-purpose rectifiers like 1N4001 are prohibited due to slow recovery causing excessive power dissipation.
How does the low-battery detection circuit behave during shutdown mode?
The low-battery detection circuit remains fully active during shutdown mode: the LBI comparator continues comparing the LBI voltage to the internal 1.28V reference, and LBO will sink current if LBI falls below threshold - enabling battery monitoring even when the main regulator is disabled.
What is the maximum inductor value recommended for MAX639ESA+ to maintain 225mA output capability?
The datasheet confirms stable 225mA operation with a 100µH inductor (L = 100µH). While larger values (e.g., 470µH) improve light-load efficiency, they reduce maximum achievable output current - Figure MAX639-07 shows maximum output current drops to ~150mA at 470µH, so 100µH is the recommended maximum for full 225mA capability.
MAX639ESA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable (Fixed)
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 11.5V
- Voltage - Output (Min/Fixed):
- 1.3V (5V)
- Voltage - Output (Max):
- 11.5V
- Current - Output:
- 225mA
- Frequency - Switching:
- -
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX639ESA+ FAQ
1.How can I place an order for MAX639ESA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX639ESA+ 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 MAX639ESA+ reliable?
The price and inventory of MAX639ESA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX639ESA+ is usually 5 days.
3.What payment methods are accepted for MAX639ESA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX639ESA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX639ESA+?
MAX639ESA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX639ESA+ 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 MAX639ESA+?
For technical support, including MAX639ESA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX639ESA+ requirements.
6.How does Aetrix verify that MAX639ESA+ is sourced from the original manufacturer or authorized distributors?
All MAX639ESA+ 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 MAX639ESA+ meets industry standards.
7.What is the process for return or replacement of MAX639ESA+?
All MAX639ESA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX639ESA+, 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 MAX639ESA+ part is unused and in its original packaging.
Return procedure for MAX639ESA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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