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Analog Devices Inc./Maxim Integrated MAX639CSA+T
- Part No.:
- MAX639CSA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX639CSA+T.pdf
- Description:
- IC REG BUCK ADJ/1.3V 225MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,905
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Product details
Overview
MAX639CSA+T 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. 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 MAX639CSA+T datasheet, MAX639CSA+T pinout, MAX639CSA+T application, or MAX639CSA+T equivalent, key selection criteria include its fixed 5V output, low-IQ PFM architecture, internal low-battery detector (LBI/LBO), SO-8 package thermal performance, and compatibility with standard 100µH inductors and Schottky diodes in minimal-component designs.
Technical Context
The MAX639CSA+T implements a current-limiting PFM control scheme that dynamically adjusts switching frequency and duty cycle to maintain constant peak inductor current (IPEAK = 50µs × VIN/L), enabling high efficiency from 10µA to 225mA load range. Its error comparator drives a variable-frequency oscillator only when output voltage dips below regulation threshold.
It integrates a 1.28V bandgap reference for both feedback (VFB) and low-battery detection (LBI), supports fixed 5V output via grounded VFB, and retains LBO functionality during shutdown. The LX pin drives external inductor with 1A peak capability and ≤1.5Ω on-resistance at +25°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 5.00V ±2% (guaranteed over 0–225mA, 4V–11.5V input) |
| Max Output Current | 225mA continuous (requires ≥100µH inductor with ≥600mA peak rating) |
| Quiescent Current | 10µA typical (enables >1-year battery life in always-on 9V systems) |
| Input Voltage Range | 4.0V to 11.5V (supports 6×AA, 9V battery, or regulated 5V–12V rails) |
| Efficiency | 89% typical at 100mA/9V input (exceeds linear regulators by >40% at medium loads) |
| LX Switch RDS(ON) | ≤1.5Ω at +25°C (minimizes dropout and conduction loss at full load) |
| Low-Battery Threshold | 1.28V ±2% on LBI pin (configurable detection point via external resistor divider) |
Pinout & Package
MAX639CSA+T is housed in an 8-pin SOIC (SO-8) package with standard .150" width, 1.27mm pitch, and exposed pad not present. Thermal resistance θJA is 5.88mW/°C above +70°C (derating to 471mW at +70°C).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT | Regulated output sense node | Internally connected to feedback 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 signaling |
| LBI | Low-battery comparator input | Monitors system battery voltage via resistor divider; remains active in shutdown mode |
| GND | Power and signal reference ground | Must be star-connected to CIN, COUT, and diode anode to minimize ground bounce |
| LX | PMOS switch drain terminal | Drives external inductor; peak current limited to 600mA to prevent saturation and IC damage |
| V+ | Positive supply input | Accepts 4V–11.5V; absolute max 12V; requires ≥33µF low-ESR input capacitor |
| VFB | Dual-mode feedback pin | Grounded for fixed 5V output; connected to external divider for adjustable outputs (1.3V–V+) |
| SHDN | Active-low shutdown control | Pulled below 0.8V disables LX; pulled above 2.0V enables operation; tie to V+ if unused |
Key Features
| Feature | Design Value |
|---|---|
| PFM Control Architecture | Enables 10µA quiescent current while maintaining >85% efficiency at 10mA load-critical for battery longevity |
| Integrated 1A PMOS Switch | Eliminates need for external MOSFET and gate driver, reducing BOM count and PCB area in space-constrained designs |
| Internal Low-Battery Detector | Provides system-level battery monitoring without additional comparators or references-reduces component count by one IC |
| Fixed 5V Output Option | Requires zero external resistors when VFB is grounded-simplifies design validation and reduces assembly cost |
| Shutdown Mode with Active LBO | Maintains battery monitoring during sleep, enabling wake-up triggers based on voltage threshold without exiting shutdown |
Applications
| Portable Medical Sensors | Handheld Test Equipment |
|---|---|
Use Scenario: Battery-powered glucose meter operating from two 3.6V Li-ion cells in series (7.2V nominal). IC Role / Device Role / Timing Role: Primary 5V power rail generator with integrated low-battery warning to alert user before measurement accuracy degrades. Use Value: 10µA IQ extends battery life beyond 2 years in standby; PFM avoids audible switching noise in sensitive analog front-end circuits. | Use Scenario: Pocket-sized multimeter powered by 9V alkaline battery with auto-ranging ADC and LCD display. IC Role / Device Role / Timing Role: Efficient 5V supply for microcontroller, display driver, and precision reference-replacing inefficient 78L05 linear regulator. Use Value: 89% efficiency at 100mA eliminates thermal derating concerns in sealed plastic enclosure; SO-8 footprint fits tight layout constraints. |
| Industrial Data Loggers | Wireless Sensor Nodes |
Use Scenario: Remote environmental monitor using 4xAA batteries (6V nominal) and LoRaWAN radio module. IC Role / Device Role / Timing Role: Main 5V supply for MCU, sensor interface, and RF transceiver-dynamically adapting to battery voltage decay from 6.8V to 4.2V. Use Value: Maintains >85% efficiency across full input range; LBO output triggers firmware-initiated data flush before brownout. | Use Scenario: Zigbee-enabled temperature node powered by CR2032 coin cell (3V) boosted via external charge pump to 5V input for MAX639CSA+T. IC Role / Device Role / Timing Role: Final-stage regulated 5V source for ultra-low-power MCU and digital sensors during active transmission bursts. Use Value: 225mA peak capability supports 100ms radio transmit pulses without output sag; PFM ensures no switching activity during 99% sleep time. |
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 |
|---|---|---|---|
| TPS62231DRVR | 3MHz PWM control (vs. PFM), 2.05V–6.5V input, 5V fixed, 300mA output, 17µA IQ | Higher switching frequency enables smaller inductors but increases EMI sensitivity; less suitable for noise-critical analog systems | Prefer for compact layouts needing <1µH inductors; avoid where audible noise or EMI must be minimized |
| LT1931ES5#TRMPBF | Fixed 5V, 1.25MHz PWM, 2.6V–16V input, 150mA output, 100µA IQ, SOT-23-5 package | Higher quiescent current reduces battery life; lower output current limits use with higher-power peripherals | Choose only when SO-8 footprint is unavailable and 150mA suffices; verify thermal performance in enclosed enclosures |
Compared with TPS62231DRVR and LT1931ES5#TRMPBF, MAX639CSA+T offers superior light-load efficiency and lower audible noise due to its PFM architecture, while delivering higher output current in the same SO-8 package-making it optimal for battery-powered instrumentation where runtime and signal integrity are critical.
Availability
MAX639CSA+T is available at Aetrix Electronics and suitable for portable medical sensors, handheld test equipment, industrial data loggers, and wireless sensor nodes requiring stable component supply with long-term manufacturability.
Supply support for MAX639CSA+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, medical, and communications markets.
The MAX639CSA+T belongs to Maxim's legacy low-power DC-DC converter family, designed specifically for battery-operated portable instrumentation where extended runtime, minimal external components, and reliable low-voltage operation are essential.
FAQ
What is the maximum input voltage rating for MAX639CSA+T?
The absolute maximum input voltage for MAX639CSA+T is 12V applied to the V+ pin. Continuous operation is specified from 4.0V to 11.5V. Exceeding 12V risks permanent damage to the internal PMOS switch and bandgap reference circuitry. For 9V battery applications, this provides 0.5V headroom against transient spikes.
Can MAX639CSA+T be used to generate an adjustable output voltage?
Yes, MAX639CSA+T supports adjustable output from 1.3V to V+ by connecting VFB to an external resistor divider instead of grounding it. The output voltage is set using R3 and R4 per the formula R3 = R4 × [(VOUT/1.28V) − 1], with R4 typically 100kΩ. This configuration maintains regulation accuracy and PFM efficiency across the full range.
Does MAX639CSA+T require an external Schottky diode?
Yes, MAX639CSA+T requires an external Schottky diode (e.g., 1N5817) connected between LX and VOUT. The IC lacks synchronous rectification, so the diode provides the freewheeling path during switch-off. Fast recovery and low forward voltage (<0.55V) are mandatory to maintain efficiency and prevent excessive heating at 225mA loads.
How does the low-battery detector function in MAX639CSA+T?
The MAX639CSA+T low-battery detector compares LBI voltage to an internal 1.28V reference. When LBI falls below 1.28V, LBO sinks current (open-drain). This circuit remains fully operational during shutdown mode. Detection threshold is set externally using R1/R2 per R1 = R2 × [(VLB/1.28V) − 1], enabling precise battery end-of-life signaling.
What is the recommended inductor value for MAX639CSA+T in a 9V-to-5V application?
For a 9V-to-5V application delivering up to 225mA, Maxim specifies a minimum 100µH inductor with ≥600mA peak current rating (e.g., Sumida CDR74-100 or equivalent). Lower inductance increases ripple and reduces efficiency; higher values improve light-load efficiency but extend start-up time. Inductor DCR should be <0.5Ω to limit dropout at full load.
MAX639CSA+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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+T FAQ
1.How can I place an order for MAX639CSA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX639CSA+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 MAX639CSA+T reliable?
The price and inventory of MAX639CSA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX639CSA+T is usually 5 days.
3.What payment methods are accepted for MAX639CSA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX639CSA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX639CSA+T?
MAX639CSA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX639CSA+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 MAX639CSA+T?
For technical support, including MAX639CSA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX639CSA+T requirements.
6.How does Aetrix verify that MAX639CSA+T is sourced from the original manufacturer or authorized distributors?
All MAX639CSA+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 MAX639CSA+T meets industry standards.
7.What is the process for return or replacement of MAX639CSA+T?
All MAX639CSA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX639CSA+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 MAX639CSA+T part is unused and in its original packaging.
Return procedure for MAX639CSA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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