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Analog Devices Inc./Maxim Integrated MAX640CSA+
- Part No.:
- MAX640CSA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX640CSA+.pdf
- Description:
- IC REG BUCK ADJ/1.3V 225MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,939
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Product details
Overview
MAX640CSA+ from Maxim Integrated is a 3.3V fixed-output, high-efficiency step-down DC-DC converter with pulse-frequency-modulated (PFM) control, delivering up to 225mA output current, 10µA quiescent supply current, and operating from 4V to 11.5V input voltage. It integrates a 1A internal PMOS power switch and features low-battery detection for portable 9V-to-3.3V conversion in handheld terminals.
For engineers reviewing the MAX640CSA+ datasheet, MAX640CSA+ pinout, MAX640CSA+ application, or MAX640CSA+ equivalent, key selection criteria include its PFM efficiency profile across light-to-moderate loads, preset 3.3V output without external feedback resistors, SO-8 package thermal performance, and compatibility with standard 100µH inductors and Schottky diodes like 1N5817.
Technical Context
The MAX640CSA+ employs a current-limiting PFM control scheme that dynamically adjusts switching frequency and duty cycle to maintain constant peak inductor current (IPEAK = 50µs × V / L), enabling high efficiency from light loads (10µA IQ) to full 225mA output. Its internal 1.28V bandgap reference feeds both the error comparator and low-battery detector.
Operation relies on variable on-time (tON = 50µs × V / (VIN − VOUT)) and minimum off-time (tOFF ≥ 50µs × V / VOUT) equations, ensuring zero-current switching and eliminating diode reverse-recovery losses. The LX pin drives an external inductor while the VFB pin supports either ground-connected fixed 3.3V mode or adjustable output via external resistor divider.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±3.7% (2.88V to 3.43V) - guaranteed over full temperature and load range without external components |
| Input Voltage Range | 4.0V to 11.5V - supports single 9V battery or regulated 5V/12V rails; dropout not specified but functional down to ~3.5V per typical curves |
| Max Output Current | 225mA - achievable with ≥100µH inductor and proper layout; limited by 600mA peak inductor current and thermal dissipation in SO-8 package |
| Quiescent Current | 10µA typical - enables >1-year battery life in always-on 9V-powered instrumentation with 25mA average load |
| Efficiency | Up to 94% at 100mA - measured with 100µH inductor, 1N5817 diode, and 9V input; maintains >85% from 1mA to 200mA load |
| Low-Battery Threshold | 1.28V ±2% on LBI pin - triggers open-drain LBO output to signal battery depletion; remains active during shutdown |
| Shutdown Threshold | 0.80V to 1.15V (SHDN pin) - ensures clean disable below 0.8V; pull-up current ≤0.4µA minimizes standby loss |
Pinout & Package
MAX640CSA+ is housed in an 8-pin SOIC (SO-8, .150" wide) package with exposed pad not present; thermal resistance θJA = 170°C/W, derating 5.88mW/°C above +70°C. Package outline conforms to MS012 standard (JEDEC MO-002AA).
| 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 3.3V 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 comparator input | Monitors battery voltage via external resistor divider; bias current <10nA minimizes divider loading |
| GND | Power and signal reference | Must be star-connected to input/output capacitor grounds and diode anode to minimize ground bounce |
| LX | PMOS switch drain terminal | Drives external inductor; peak current capability limited to 600mA; requires low-ESR catch diode |
| V+ | Positive supply input | Accepts 4–11.5V; absolute max 12V; bypass with ≥33µF electrolytic or low-ESR ceramic capacitor |
| VFB | Dual-mode feedback pin | Grounded for fixed 3.3V operation; connected to resistor divider for adjustable outputs (1.3V–VIN) |
| SHDN | Active-low enable control | Pulled below 0.8V disables regulator; leakage <0.4µA allows direct microcontroller GPIO drive |
Key Features
| Feature | Design Value |
|---|---|
| PFM control architecture | Enables 10µA quiescent current and >85% efficiency at 1mA load-critical for battery longevity in portable instruments |
| Integrated 1A PMOS switch | Eliminates external MOSFET and gate driver, reducing BOM count and PCB area in space-constrained handheld designs |
| Fixed 3.3V output (VFB grounded) | Removes need for precision feedback resistors, simplifying design validation and reducing calibration overhead |
| Active low-battery comparator | Provides system-level battery monitoring without additional ICs; operates during shutdown to preserve state awareness |
| Zero-current switching | Minimizes diode reverse-recovery losses and EMI, enabling use of low-cost 1N5817 instead of ultrafast diodes |
Applications
| Portable Instrument Power | Handheld Terminal Conversion |
|---|---|
|
Use Scenario: Powering digital multimeters, gas detectors, or portable oscilloscopes from a single 9V alkaline battery. IC Role / Device Role / Timing Role: Primary 3.3V step-down regulator supplying microcontroller, display, and sensor interface rails. Use Value: 10µA quiescent current extends battery life beyond 12 months in sleep mode; PFM efficiency maintains >90% at 5mA typical operating load. |
Use Scenario: Converting 9V battery voltage to stable 3.3V for ARM Cortex-M0/M3-based handheld data collectors. IC Role / Device Role / Timing Role: Core power management IC enabling low-power MCU operation and RF module sequencing. Use Value: Integrated low-battery detection (LBI/LBO) eliminates need for separate supervisor IC, reducing component count by one. |
| 5V-to-3.3V Point-of-Load | Industrial Sensor Node Supply |
|
Use Scenario: Generating 3.3V from existing 5V system rail in PLC I/O modules or industrial controllers. IC Role / Device Role / Timing Role: Local DC-DC converter replacing linear regulator to reduce thermal load on 5V supply. Use Value: 94% peak efficiency reduces heat generation by >70% versus LDO, enabling higher channel density in compact enclosures. |
Use Scenario: Powering wireless sensor nodes (LoRaWAN, NB-IoT) with intermittent 225mA burst transmission from AA/AAA batteries. IC Role / Device Role / Timing Role: High-efficiency buck converter supporting pulsed load profiles with fast transient response. Use Value: 25µs LBO delay and sub-10ms startup time ensure reliable brown-out detection and rapid wake-up from deep sleep. |
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 |
|---|---|---|---|
| TPS62231DRYR | 3.3V fixed, 300mA output, 17µA IQ, PWM-only control (no PFM), 2.05–6.5V input | Higher output current but lower light-load efficiency; requires external compensation; no integrated LBO | Select when higher continuous current or tighter output tolerance (±1%) is required; avoid if battery life at µA loads is critical |
| RT8059GJ6 | 3.3V fixed, 300mA, 22µA IQ, PFM/PWM hybrid, 2.5–5.5V input, no LBI/LBO | Narrower input range; lacks battery monitoring; smaller 6-pin SOT-23-6 package limits thermal headroom | Prefer for space-constrained designs where input is regulated 3.3V/5V and battery detection is handled externally |
Compared with TPS62231DRYR and RT8059GJ6, the MAX640CSA+ uniquely combines ultra-low 10µA quiescent current, integrated low-battery detection, and wide 4–11.5V input range-making it optimal for unregulated battery-powered systems requiring long service life and autonomous battery management.
Availability
MAX640CSA+ is available at Aetrix Electronics and suitable for portable instrumentation, handheld terminals, industrial sensor nodes, and 5V-to-3.3V point-of-load conversion requiring stable component supply and long-term manufacturability.
Supply support for MAX640CSA+ 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, medical, and portable applications.
The MAX639/MAX640/MAX653 family was designed specifically for battery-powered systems needing high-efficiency, low-quiescent-current DC-DC conversion with integrated system supervision functions like low-battery detection.
FAQ
What is the maximum output current capability of the MAX640CSA+ under typical conditions?
The MAX640CSA+ delivers up to 225mA output current with a 100µH inductor, 1N5817 diode, and 9V input at +25°C. Performance depends on thermal management: the SO-8 package's 471mW continuous power dissipation limit and ambient temperature constrain sustained 225mA operation. At 100mA, efficiency reaches 94%; at 10mA, it remains above 85% due to PFM control.
Can the MAX640CSA+ be used in adjustable-output configurations?
Yes, the MAX640CSA+ supports adjustable output voltages from 1.3V to VIN by connecting VFB to an external resistor divider instead of grounding it. The feedback threshold is 1.28V, so R3 = R4 × ((VOUT/1.28) − 1). For example, to set 2.5V output with R4 = 100kΩ, R3 = 95.3kΩ. Fixed 3.3V operation requires only grounding VFB-no resistors needed.
How does the low-battery detection function work on the MAX640CSA+?
The MAX640CSA+ uses an internal 1.28V reference to compare against the voltage applied to the LBI pin. When LBI falls below 1.28V, the open-drain LBO pin pulls low, sinking up to 2.5mA. This comparator remains active during shutdown mode. To set a 6.0V low-battery threshold, use R1 = R2 × ((6.0/1.28) − 1); with R2 = 100kΩ, R1 = 369kΩ. LBO leakage is <0.1µA when inactive.
What external components are required for basic operation of the MAX640CSA+?
For fixed 3.3V operation, the MAX640CSA+ requires only four external components: an input capacitor (≥33µF), output capacitor (≥100µF), 100µH inductor, and Schottky diode (e.g., 1N5817). VFB is grounded, SHDN is tied to V+, and LBI/LBO are left unconnected unless battery monitoring is needed. No feedback resistors or compensation networks are required in default configuration.
Is the MAX640CSA+ pin-compatible with other devices in the MAX639/MAX640/MAX653 family?
Yes, all members of the MAX639/MAX640/MAX653 family-including MAX640CSA+-share identical 8-pin SOIC pinouts, electrical interfaces, and PCB footprints. The only functional difference is the preset output voltage: MAX639 = 5.0V, MAX640 = 3.3V, MAX653 = 3.0V. This allows drop-in replacement across variants when adjusting system voltage rails without layout changes.
MAX640CSA+ 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 (3.3V)
- 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
MAX640CSA+ FAQ
1.How can I place an order for MAX640CSA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX640CSA+ 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 MAX640CSA+ reliable?
The price and inventory of MAX640CSA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX640CSA+ is usually 5 days.
3.What payment methods are accepted for MAX640CSA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX640CSA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX640CSA+?
MAX640CSA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX640CSA+ 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 MAX640CSA+?
For technical support, including MAX640CSA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX640CSA+ requirements.
6.How does Aetrix verify that MAX640CSA+ is sourced from the original manufacturer or authorized distributors?
All MAX640CSA+ 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 MAX640CSA+ meets industry standards.
7.What is the process for return or replacement of MAX640CSA+?
All MAX640CSA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX640CSA+, 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 MAX640CSA+ part is unused and in its original packaging.
Return procedure for MAX640CSA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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