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Analog Devices Inc./Maxim Integrated MAX639CSA+
- Part No.:
- MAX639CSA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX639CSA+.pdf
- Description:
- IC REG BUCK ADJ/1.3V 225MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,120
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Product details
Overview
MAX639CSA+ from Maxim Integrated is a 5V fixed-output, high-efficiency step-down DC-DC switching regulator with internal 1A PMOS power switch, 10µA quiescent current, and 4V–11.5V input range. It delivers up to 225mA output current and integrates low-battery detection (LBI/LBO) for portable 9V-to-5V conversion in battery-powered instrumentation.
For engineers reviewing the MAX639CSA+ datasheet, MAX639CSA+ pinout, MAX639CSA+ application, or MAX639CSA+ equivalent, key selection criteria include its PFM control scheme enabling high efficiency across light-to-heavy loads, SO-8 package compatibility with space-constrained PCBs, preset 5V output eliminating external feedback resistors, and guaranteed operation from 0°C to +70°C.
Technical Context
The MAX639CSA+ uses a current-limiting pulse-frequency-modulated (PFM) control architecture that dynamically adjusts switching frequency and duty cycle to maintain constant peak inductor current (IPEAK = 50µs × VIN/L), ensuring stable regulation without external compensation. Its internal 1A PMOS switch eliminates external drive circuitry and supports both buck and inverting configurations.
It features dual-mode feedback via VFB: grounding VFB selects the factory-trimmed 5.00V ±2% output; connecting VFB to an external divider enables adjustable outputs from 1.3V to VIN. The integrated low-battery comparator (1.28V threshold on LBI) remains active during shutdown and drives open-drain LBO.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 5.00V ±2% (factory-trimmed, no external resistors required) |
| Input Voltage Range | 4.0V to 11.5V - supports single 9V battery or regulated 5V–12V rails |
| Max Output Current | 225mA - achievable with ≥100µH inductor and low-ESR output capacitor |
| Quiescent Supply Current | 10µA - enables >1-year battery life in always-on portable devices |
| Efficiency | Up to 91% at 100mA (VIN = 9V, L = 100µH) - exceeds linear regulators under medium load |
| Low-Battery Threshold | 1.28V ±20mV on LBI - configurable detection voltage via external resistor divider |
| Shutdown Threshold | SHDN < 0.8V (active-low) - reduces total system current to <1µA in sleep mode |
Pinout & Package
MAX639CSA+ is housed in an 8-pin SOIC (SO) package with 150-mil body width, JEDEC MS-012AC compliant, and RoHS-compliant lead finish.
| 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 indicator output | Sinks up to 10mA when LBI falls below 1.28V; requires external pull-up for logic-level signaling |
| LBI | Low-battery detection input | Compares external voltage (e.g., battery tap) against 1.28V reference; remains active in shutdown |
| GND | Power and signal ground reference | Must be star-connected with CIN, COUT, and diode anode to minimize ground bounce |
| LX | PMOS switch drain terminal | Drives external inductor; peak current limited to 600mA; requires Schottky catch diode (e.g., 1N5817) |
| V+ | Positive supply input | Accepts 4V–11.5V; absolute max 12V; decoupling capacitor (≥33µF) required at pin |
| VFB | Dual-mode feedback input | Grounded for 5V fixed output; connected to resistor divider for adjustable output (1.3V–VIN) |
| SHDN | Active-low shutdown control | Pulled below 0.8V disables LX switching and reduces supply current to <1µA |
Key Features
| Feature | Design Value |
|---|---|
| PFM control architecture | Delivers >85% efficiency at 1mA load and >90% at 100mA - eliminates efficiency cliff of PWM at light loads |
| Integrated 1A PMOS switch | Reduces BOM count by eliminating external MOSFET driver; supports inverting configuration for negative rail generation |
| Factory-trimmed 5V output | Eliminates external feedback resistors and layout sensitivity - simplifies design and improves production yield |
| Low-battery detection with LBO | Enables system-level battery monitoring without additional comparators - saves board space and cost |
| 10µA quiescent current | Extends battery runtime in standby mode - critical for handheld test equipment and remote sensors |
Applications
| Portable Instrumentation | 9V Battery-Powered Devices |
|---|---|
Use Scenario: Handheld multimeters and data loggers powered by a single 9V alkaline battery. IC Role / Device Role / Timing Role: Primary 5V power rail generator replacing inefficient 78L05 linear regulator. Use Value: Extends battery life from ~200 hours to >1000 hours at 10mA average load while maintaining tight 5V regulation. |
Use Scenario: Wireless sensor nodes requiring reliable 5V supply from aging 9V batteries. IC Role / Device Role / Timing Role: Buck converter with integrated low-battery warning (LBI/LBO) for graceful shutdown. Use Value: Enables early battery depletion detection before system brownout - prevents data corruption in flash memory writes. |
| Industrial Control Interfaces | Embedded Microcontroller Power |
Use Scenario: DIN-rail mounted I/O modules converting 12V bus to isolated 5V logic supply. IC Role / Device Role / Timing Role: Compact, low-noise 5V source for RS-485 transceivers and optocouplers. Use Value: Achieves <15mVpp output ripple with 100µF/0.1µF ceramic parallel filter - meets EMC immunity requirements. |
Use Scenario: Powering ARM Cortex-M0+ microcontrollers in compact edge devices. IC Role / Device Role / Timing Role: Primary 5V VDD supply with fast start-up (<10ms to 5V at 100mA) after wake-from-sleep. Use Value: Supports rapid MCU wake-up cycles without voltage droop - maintains real-time responsiveness. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down DC-DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX640CSA+ | Fixed 3.3V output (±2%), identical pinout and package, same 10µA IQ and 225mA capability | Used where 3.3V logic rails replace legacy 5V systems - no change to PCB layout or inductor/diode selection | Select when system voltage scaling mandates 3.3V instead of 5V; shares identical thermal and EMI behavior |
| TPS62231DRYR | 3MHz fixed-frequency PWM (vs. PFM), 2.05V–6.5V input, 5V output, 300mA rating, 17µA IQ | Better suited for noise-sensitive analog circuits due to fixed frequency; requires external feedback resistors | Choose for EMI-controlled environments where switching frequency predictability outweighs light-load efficiency loss |
Compared with MAX640CSA+, the MAX639CSA+ provides higher output voltage for legacy 5V peripherals but identical footprint and thermal performance; versus TPS62231DRYR, it trades fixed-frequency EMI control for superior light-load efficiency and zero-resistor simplicity.
Availability
MAX639CSA+ is available at Aetrix Electronics and suitable for portable instrumentation, 9V battery-powered devices, and industrial control interfaces requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for MAX639CSA+ 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 industrial, medical, and communications applications.
The MAX639CSA+ belongs to Maxim's high-efficiency, low-IQ DC-DC converter family targeting battery-operated and energy-conscious systems where extended runtime and minimal external components are critical.
FAQ
What is the maximum input voltage rating for the MAX639CSA+?
The MAX639CSA+ has an absolute maximum input voltage (V+) of 12V. Its recommended operating range is 4.0V to 11.5V. Exceeding 12V risks permanent damage to the internal PMOS switch and bandgap reference. For reliable 9V battery applications, the MAX639CSA+ maintains regulation even as the battery discharges from 9.6V down to 4.0V, making it ideal for long-life portable designs.
Does the MAX639CSA+ require external feedback resistors to deliver 5V output?
No, the MAX639CSA+ does not require external feedback resistors for 5V operation. When VFB is grounded, the device uses its internal trimmed voltage divider to regulate precisely to 5.00V ±2%. This eliminates resistor tolerance errors, layout parasitics, and BOM cost - a key differentiator versus adjustable-only converters like the MAX649 series.
Can the MAX639CSA+ be used in an inverting configuration to generate -5V?
Yes, the MAX639CSA+ supports inverting operation. By connecting the standard output node to system ground and referencing the IC's GND pin to the negative rail, it generates a regulated -5V output. This configuration leverages the same internal 1A PMOS switch and maintains efficiency above 84% at 10mA with 470µH inductance, as verified in Maxim's Figure 6–8 test circuits.
What is the purpose of the LBI and LBO pins on the MAX639CSA+?
The LBI (Low-Battery Input) and LBO (Low-Battery Output) pins implement a dedicated battery-monitoring function. LBI compares an external voltage (e.g., battery divider) to a precise 1.28V internal reference; when LBI drops below threshold, LBO - an open-drain N-channel MOSFET - pulls low. This occurs even during SHDN mode, enabling system-level battery-aware shutdown without additional components.
How does the PFM control scheme of the MAX639CSA+ improve efficiency compared to PWM converters?
The MAX639CSA+ uses pulse-frequency modulation (PFM) to vary switching frequency inversely with load - delivering only the energy needed per cycle. At 1mA load, it draws just 10µA supply current (vs. 2–10mA for PWM), achieving >85% efficiency where PWM converters drop below 50%. This eliminates the "efficiency cliff" and extends battery life in intermittent-use applications like remote sensors.
MAX639CSA+ 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:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX639CSA+ FAQ
1.How can I place an order for MAX639CSA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX639CSA+ 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 MAX639CSA+ reliable?
The price and inventory of MAX639CSA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX639CSA+ is usually 5 days.
3.What payment methods are accepted for MAX639CSA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX639CSA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX639CSA+?
MAX639CSA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX639CSA+ 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 MAX639CSA+?
For technical support, including MAX639CSA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX639CSA+ requirements.
6.How does Aetrix verify that MAX639CSA+ is sourced from the original manufacturer or authorized distributors?
All MAX639CSA+ 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 MAX639CSA+ meets industry standards.
7.What is the process for return or replacement of MAX639CSA+?
All MAX639CSA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX639CSA+, 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 MAX639CSA+ part is unused and in its original packaging.
Return procedure for MAX639CSA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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