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Analog Devices Inc./Maxim Integrated MAX639CPA
- Part No.:
- MAX639CPA
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
MAX639CPA.pdf
- Description:
- IC REG BUCK ADJ/1.3V 225MA 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,828
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Product details
Overview
The MAX639CPA from Maxim Integrated is a 5V, 225mA step-down DC-DC switching regulator with pulse-frequency-modulated (PFM) control, 10µA quiescent current, and integrated 1A PMOS power switch in an 8-pin plastic DIP package. It operates from 4V to 11.5V input and delivers high efficiency across light-to-heavy loads-ideal for 9V battery-powered portable instruments requiring stable 5V rail generation.
For engineers reviewing the MAX639CPA datasheet, MAX639CPA pinout, MAX639CPA application, or MAX639CPA equivalent, key selection criteria include its low-IQ PFM architecture, preset 5V output, internal low-battery comparator (LBI/LBO), shutdown control (SHDN), and compatibility with standard 100µH inductors and Schottky diodes in minimal-component buck designs.
Technical Context
The MAX639CPA implements a variable-frequency, current-limiting PFM control scheme that dynamically adjusts on-time (tON = 50µs × VIN/(VIN − VOUT)) and off-time (tOFF ≥ 50µs × VIN/VOUT) to maintain constant peak inductor current (~600mA) across input voltage variations. Its error comparator references a 1.28V internal bandgap and drives a variable-duty-cycle oscillator only when regulation is needed.
It integrates a low-battery detector with 1.28V threshold on LBI, open-drain LBO output, and active operation during shutdown. The VFB pin supports both fixed 5V output (when grounded) and adjustable output via external resistor divider, while SHDN enables active-low enable/disable with 0.8V–2.0V logic thresholds.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Preset 5.0V ±2% (guaranteed by correlation to switch timing and feedback parameters) |
| Max Output Current | 225mA continuous at VIN = 9V, L = 100µH (limited by thermal dissipation and inductor saturation) |
| Quiescent Current | 10µA typical at no load - enables >1-year battery life in always-on portable devices |
| Input Voltage Range | 4.0V to 11.5V - supports single 9V alkaline or dual Li-ion configurations |
| Efficiency | 89% typical at 100mA, VIN = 9V, L = 100µH - exceeds linear regulators under medium loads |
| Switch On-Resistance | 0.8Ω typical - minimizes dropout and conduction loss in PMOS switch |
| Low-Battery Threshold | 1.28V ±20mV on LBI - sets precise undervoltage lockout without external reference |
Pinout & Package
Package: 8-pin plastic DIP (0.300" wide), through-hole mount, operating temperature range 0°C to +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 2.5mA when LBI < 1.28V; requires external pull-up for logic-level signaling |
| LBI | Low-battery detection input | Compares external voltage (e.g., battery tap) to 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 capability limited to 600mA to avoid saturation |
| V+ | Positive supply input | Accepts 4V–11.5V; absolute max 12V; decoupling capacitor required within 1cm |
| VFB | Dual-mode feedback input | Grounded for 5V fixed output; used with resistor divider for adjustable outputs (1.3V–VIN) |
| SHDN | Active-low shutdown control | Pulled below 0.8V disables LX; pulled above 2.0V enables regulation; tie to V+ if unused |
Key Features
| Feature | Design Value |
|---|---|
| PFM Control Architecture | Enables 10µA quiescent current and >85% efficiency at 1mA load - critical for battery longevity |
| Integrated 1A PMOS Switch | Eliminates external MOSFET and gate driver - reduces BOM count and layout complexity |
| Preset 5V Output | Requires zero external resistors when VFB = GND - simplifies design for standard 5V rails |
| Active Low-Battery Detector | Provides system-level battery monitoring without additional ICs or firmware polling |
| Shutdown Mode with LBO Active | Reduces total system power to µA level while preserving battery status visibility |
Applications
| 9V Battery to 5V Conversion | High-Efficiency Linear Regulator Replacement |
|---|---|
Use Scenario: Powering microcontroller-based handheld terminals from a single 9V alkaline battery. IC Role / Device Role / Timing Role: Primary 5V DC-DC converter delivering up to 225mA with PFM modulation to extend battery life. Use Value: Achieves 89% efficiency at 100mA vs. ~45% for 78L05 linear regulator - doubles usable battery capacity. | Use Scenario: Replacing obsolete 7805 linear regulators in industrial sensor nodes with tight thermal constraints. IC Role / Device Role / Timing Role: Step-down switching regulator providing regulated 5V output with minimal heat dissipation. Use Value: Dissipates only 120mW at 100mA (vs. 400mW for 7805), enabling operation in sealed enclosures without heatsinking. |
| Portable Instruments | 5V-to-3.3V Converter Interface |
Use Scenario: Supplying 5V rail to analog front-end and display in portable multimeters. IC Role / Device Role / Timing Role: Main power converter with integrated LBO for battery gauge functionality. Use Value: Combines regulation and battery monitoring in one IC - eliminates separate supervisor IC and saves PCB area. | Use Scenario: Generating clean 5V for MCU core while feeding downstream 3.3V LDO in mixed-voltage systems. IC Role / Device Role / Timing Role: High-efficiency pre-regulator reducing input voltage to optimize LDO efficiency and thermal margin. Use Value: Lowers LDO dropout requirement by 4V - allows use of lower-IQ, smaller-footprint LDOs with improved PSRR. |
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 |
|---|---|---|---|
| MAX640CPA | Fixed 3.3V output (not 5V); identical pinout, package, and PFM architecture | Used where 3.3V logic rail is required instead of 5V; same external component values apply | Select MAX640CPA only when system requires 3.3V - not a drop-in replacement for 5V designs |
| TPS62231DRVR | 3MHz PWM (not PFM); 2.05–6.0V input; 5V output; 300mA rating; 2mm × 2mm WSON-6 | Higher frequency enables smaller inductors/capacitors but higher light-load IQ (17µA vs. 10µA) | Choose TPS62231DRVR for space-constrained designs needing higher output current; accept trade-off in standby power |
Compared with MAX640CPA and TPS62231DRVR, the MAX639CPA uniquely balances ultra-low quiescent current (10µA), fixed 5V output, and through-hole DIP packaging - making it optimal for legacy-replacement, battery-life-critical, and serviceable industrial instruments.
Availability
MAX639CPA is available at Aetrix Electronics and suitable for 9V battery-powered portable instruments, high-efficiency linear regulator replacements, and industrial sensor nodes requiring stable component supply and long-term obsolescence support.
Supply support for MAX639CPA 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 semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and communications applications.
The MAX639CPA belongs to Maxim's legacy low-power DC-DC converter product line, designed specifically for battery-operated equipment requiring high efficiency across wide load ranges and integrated system supervision features.
FAQ
What is the maximum input voltage rating for the MAX639CPA?
The MAX639CPA has an absolute maximum input voltage rating of 12V on the V+ pin. Its recommended operating input range is 4.0V to 11.5V. Exceeding 12V may cause permanent damage. This limit ensures safe operation with common 9V batteries, even under no-load transient conditions where input voltage can rise due to source impedance.
Does the MAX639CPA require external components to deliver its preset 5V output?
No, the MAX639CPA delivers its preset 5V output with zero external resistors when the VFB pin is connected directly to GND. Only three external components are mandatory: an inductor (≥100µH), a Schottky diode (e.g., 1N5817), and input/output capacitors. This minimal BOM reduces cost and layout risk in high-volume portable instrument designs.
How does the low-battery detection feature work on the MAX639CPA?
The MAX639CPA's low-battery detector compares voltage on the LBI pin to an internal 1.28V reference. When LBI falls below this threshold, the open-drain LBO pin pulls low. LBO remains functional during shutdown mode. Users set detection voltage using a resistor divider (e.g., R1/R2) from battery to GND, with LBI connected to the divider midpoint - enabling customizable battery cutoff without extra ICs.
Can the MAX639CPA be used in an inverting configuration to generate -5V?
Yes, the MAX639CPA supports inverting operation: connect VOUT to system ground, tie the former ground node to VIN, and route the LX output through an inductor/diode to generate -5V at the new "output" node. The datasheet confirms this topology (Figure 6) with efficiency >84% at 10mA and maximum differential voltage limited to 11.5V between V+ and VOUT - ensuring safe operation in bipolar supply designs.
What is the thermal performance of the MAX639CPA in its plastic DIP package?
In its 8-pin plastic DIP package, the MAX639CPA has a continuous power dissipation limit of 727mW at +70°C ambient, derating by 9.09mW/°C above that temperature. At full 225mA output into 5V with 9V input, power dissipation is ~900mW - exceeding the package limit. Therefore, operation at full load requires either reduced ambient temperature, forced airflow, or careful thermal design with copper pour to meet reliability targets.
MAX639CPA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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:
- Through Hole
- Supplier Device Package:
- 8-PDIP
MAX639CPA FAQ
1.How can I place an order for MAX639CPA through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX639CPA 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 MAX639CPA reliable?
The price and inventory of MAX639CPA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX639CPA is usually 5 days.
3.What payment methods are accepted for MAX639CPA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX639CPA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX639CPA?
MAX639CPA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX639CPA 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 MAX639CPA?
For technical support, including MAX639CPA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX639CPA requirements.
6.How does Aetrix verify that MAX639CPA is sourced from the original manufacturer or authorized distributors?
All MAX639CPA 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 MAX639CPA meets industry standards.
7.What is the process for return or replacement of MAX639CPA?
All MAX639CPA units undergo pre-shipment inspection (PSI). If there is an issue with MAX639CPA, 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 MAX639CPA part is unused and in its original packaging.
Return procedure for MAX639CPA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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