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Analog Devices Inc./Maxim Integrated MAX640C/D
- Part No.:
- MAX640C/D
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- -
- Datasheet:
-
MAX640C/D.pdf
- Description:
- IC REG DC-DC CONVERTERS
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Product details
Overview
MAX640C/D from Maxim Integrated is a 3.3V 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 (1.28V threshold) for portable instrumentation and battery-powered 9V-to-3.3V conversion.
For engineers reviewing the MAX640C/D datasheet, MAX640C/D pinout, MAX640C/D application, or MAX640C/D equivalent, key selection considerations include its PFM control scheme enabling high efficiency across light-to-heavy loads, preset 3.3V output eliminating external feedback resistors, and SO package compatibility with standard surface-mount assembly processes.
Technical Context
The MAX640C/D employs a current-limiting pulse-frequency-modulated (PFM) control architecture that dynamically adjusts switching frequency and duty cycle to maintain constant peak inductor current (via tON = 50µs × VIN/(VIN − VOUT) and tOFF ≥ 50µs × VIN/VOUT). This enables high efficiency (up to 94%) from 10µA no-load to 225mA full load without requiring external compensation.
It integrates a precision 1.28V bandgap reference shared by both the error comparator and low-battery detector, allowing simultaneous regulation and battery monitoring. The LBI/LBO pins operate independently of shutdown mode, maintaining battery status visibility even when the regulator is disabled.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±3% (guaranteed over temperature and line/load) |
| Input Voltage Range | 4.0V to 11.5V - supports single 9V battery, dual AA/AAA, or industrial 5V–12V rails |
| Max Output Current | 225mA - achievable with ≥100µH inductor and proper layout to limit peak current to 600mA |
| Quiescent Supply Current | 10µA typical - enables >1-year battery life in always-on portable sensors |
| Efficiency | 94% at 100mA (VIN = 6V, L = 100µH) - exceeds linear regulators by >40 percentage points at medium load |
| Low-Battery Threshold | 1.28V ±2% on LBI pin - sets precise battery depletion point for system-level power management |
| Shutdown Threshold | 0.80V to 1.15V (SHDN pin) - provides clean, noise-immune enable/disable control |
Pinout & Package
MAX640C/D is supplied in an 8-pin SO (Small Outline) package per JEDEC MS-012, 150-mil body width, with lead finish SnPb or RoHS-compliant matte tin.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT | Regulated output voltage node | Direct connection to output filter capacitor and load; internally tied to feedback divider for 3.3V setting |
| LBO | Open-drain low-battery indicator output | Sinks up to 10mA when LBI < 1.28V; requires external pull-up for logic-level interface |
| LBI | Low-battery sense input | Monitors battery voltage via external resistor divider; remains active during SHDN |
| 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; switches between VIN and GND; peak current limited to 1A |
| V+ | Positive supply input | Accepts 4V–11.5V; must be bypassed with ≥33µF low-ESR capacitor near pin |
| VFB | Dual-mode feedback pin | Grounded for 3.3V fixed output; connected to external divider for adjustable operation |
| SHDN | Active-low shutdown control | Pulled below 0.8V disables LX; pulled above 2.0V enables regulation; internal 0.2µA pull-up |
Key Features
| Feature | Design Value |
|---|---|
| PFM control with variable frequency | Maintains >85% efficiency from 10µA to 225mA load without external compensation |
| Integrated 1A PMOS power switch | Eliminates need for external MOSFET and gate driver; reduces BOM count and PCB area |
| Preset 3.3V output | Requires zero external components for fixed-voltage operation - simplifies design and validation |
| Independent low-battery monitor | 1.28V comparator with LBI/LBO pins remains functional during shutdown for battery state awareness |
| Ultra-low 10µA quiescent current | Enables micropower operation in battery-backed real-time clocks, IoT edge nodes, and wearables |
Applications
| Handheld Test Equipment | Industrial Sensor Transmitters |
|---|---|
|
Use Scenario: Portable multimeter powered by 9V alkaline battery requiring stable 3.3V for MCU, ADC, and display backlight. IC Role / Device Role / Timing Role: Primary 9V-to-3.3V DC-DC converter supplying regulated power to mixed-signal subsystems. Use Value: 94% efficiency at 100mA extends battery life to >200 hours; PFM operation eliminates audible switching noise in sensitive analog front-ends. |
Use Scenario: 4–20mA loop-powered temperature transmitter operating from 12–24V supply with onboard 3.3V microcontroller and signal conditioning. IC Role / Device Role / Timing Role: Local point-of-load regulator converting loop-derived voltage to clean 3.3V rail. Use Value: 10µA quiescent current ensures minimal impact on loop compliance voltage; integrated LBI allows battery backup monitoring without extra IC. |
| Medical Point-of-Care Devices | Wireless Remote Sensors |
|
Use Scenario: Battery-operated glucose meter using two AAA cells (2.4–3.2V) boosted to 3.3V for LCD and Bluetooth LE radio. IC Role / Device Role / Timing Role: Step-down regulator in inverting configuration to generate negative bias for LCD contrast control. Use Value: Fixed 3.3V output eliminates feedback resistor tolerance errors; LBO alerts firmware when battery drops below 2.7V under load. |
Use Scenario: LoRaWAN soil moisture sensor deployed in remote fields, powered by primary lithium thionyl chloride cell (3.6V). IC Role / Device Role / Timing Role: Always-on power manager delivering 3.3V to ultra-low-power MCU and RF transceiver during periodic wake-ups. Use Value: 10µA IQ enables >10-year field lifetime; PFM operation avoids fixed-frequency EMI interference with narrowband RF reception. |
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, 17µA IQ, 300mA output, 2.05–6.0V input, requires external compensation | Lower input voltage ceiling limits use with 9V batteries; higher IQ reduces battery life in micropower apps | Select when input is strictly ≤6V and higher output current is required; verify stability with external RC network |
| LT1931ES5#TRMPBF | Adjustable output, 100µA IQ, 1.25A switch, 2.6–16V input, requires external feedback resistors | Higher IQ increases no-load power draw; adjustable output adds component count and calibration complexity | Choose for wide-input industrial supplies where 3.3V accuracy is secondary to input voltage flexibility |
Compared with TPS62231DRYR and LT1931ES5#TRMPBF, the MAX640C/D offers the lowest quiescent current (10µA) and simplest fixed-output implementation for 4–11.5V inputs, making it optimal for battery longevity and design simplicity in portable instrumentation.
Availability
MAX640C/D is available at Aetrix Electronics and suitable for handheld test equipment, industrial sensor transmitters, medical point-of-care devices, and wireless remote sensors requiring stable component supply with long-term manufacturability.
Supply support for MAX640C/D 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 demanding industrial, medical, and communications applications.
The MAX640C/D belongs to Maxim's legacy high-efficiency, low-IQ DC-DC converter family targeting portable and battery-critical systems where extended runtime and minimal external components are essential.
FAQ
What is the guaranteed output voltage tolerance for MAX640C/D across temperature and load?
The MAX640C/D guarantees 3.3V output within ±3% over the full 0°C to +70°C operating temperature range and for load currents from 0mA to 225mA. This specification is validated per the Electrical Characteristics table in the datasheet, with typical deviation of ±1.2% at +25°C and 100mA load. The MAX640C/D achieves this using a trimmed internal voltage divider referenced to a precision 1.28V bandgap.
Can MAX640C/D operate from a single 3.7V Li-ion cell?
No, the MAX640C/D requires a minimum input voltage of 4.0V per Absolute Maximum Ratings and Electrical Characteristics tables. A discharged 3.7V Li-ion cell falls below this threshold, causing dropout and regulation loss. For Li-ion applications, consider the MAX640C/D only with fully charged cells (≥4.2V) or paired with a boost stage; alternative parts like the MAX17222 are better suited for 2.5V–5.5V inputs.
Does MAX640C/D require an external Schottky diode, and what is the recommended part?
Yes, the MAX640C/D requires an external Schottky diode for flyback current path during switch-off. The datasheet specifies the 1N5817 (or equivalent) as the preferred part due to its 0.55V forward voltage and fast recovery. Surface-mount alternatives include SE014 (SOT-89) or equivalents with IF(AV) ≥ 300mA and VF ≤ 0.6V at 200mA. Standard rectifiers like 1N4001 must be avoided due to slow reverse recovery causing excessive losses.
How does the low-battery detector function when MAX640C/D is in shutdown mode?
The low-battery detector remains fully operational during shutdown: the LBI comparator continues comparing the LBI voltage against the internal 1.28V reference, and LBO will sink current if LBI drops below threshold - even while LX is disabled and VOUT is unregulated. This allows host systems to monitor battery health independently of power state, a feature confirmed in the Shutdown Mode section of the datasheet.
What is the maximum allowable inductor value for MAX640C/D, and why is there a lower limit of 100µH?
The datasheet specifies a minimum inductor value of 100µH but does not define a hard upper limit. Larger inductors (e.g., 470µH) reduce ripple and improve light-load efficiency but increase start-up time and physical size. The 100µH minimum ensures peak inductor current stays ≤600mA (per Equation 3: IPEAK = 50µs × VIN/L), preventing saturation and switch overstress - a requirement explicitly stated in Note 1 of the Electrical Characteristics table.
MAX640C/D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Function:
- -
- Output Configuration:
- -
- Topology:
- -
- Output Type:
- -
- Number of Outputs:
- -
- Voltage - Input (Min):
- -
- Voltage - Input (Max):
- -
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- -
- Frequency - Switching:
- -
- Synchronous Rectifier:
- -
- Operating Temperature:
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- Grade:
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- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
MAX640C/D FAQ
1.How can I place an order for MAX640C/D through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX640C/D 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 MAX640C/D reliable?
The price and inventory of MAX640C/D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX640C/D is usually 5 days.
3.What payment methods are accepted for MAX640C/D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX640C/D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX640C/D?
MAX640C/D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX640C/D 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 MAX640C/D?
For technical support, including MAX640C/D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX640C/D requirements.
6.How does Aetrix verify that MAX640C/D is sourced from the original manufacturer or authorized distributors?
All MAX640C/D 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 MAX640C/D meets industry standards.
7.What is the process for return or replacement of MAX640C/D?
All MAX640C/D units undergo pre-shipment inspection (PSI). If there is an issue with MAX640C/D, 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 MAX640C/D part is unused and in its original packaging.
Return procedure for MAX640C/D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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