LM431CCMX

Product Overview: onsemi LM431CCMX

The onsemi LM431CCMX is a precision adjustable shunt voltage regulator designed to provide a stable and accurate voltage reference in various electronic circuits. It operates similarly to a Zener diode but with significantly improved performance characteristics such as adjustable output voltage, low dynamic impedance, and high stability over temperature and supply variations. The LM431CCMX is widely used in power supplies, voltage monitoring, and regulation applications, offering a compact and reliable solution for voltage reference needs.

Key Features

* Adjustable Output Voltage: Output voltage programmable from 2.5 V to 36 V by an external resistor divider.
* Low Dynamic Impedance: Typically 0.2 Ω at 10 mA, providing superior voltage regulation performance.
* Wide Operating Voltage Range: Supports voltages up to 36 V, suitable for many applications.
* High Accuracy: Initial output voltage tolerance of ±1% with tight temperature stability.
* Low Temperature Drift: Approximately 50 ppm/°C, ensuring consistent performance over temperature variations.
* Wide Operating Current Range: Operates from 1 mA to 100 mA, supporting various load conditions.
* Fast Response Time: Suitable for transient voltage regulation.
* Thermal Shutdown Protection: Internal thermal protection prevents damage during over-temperature conditions.
* Surface Mount Package: Available in SOIC-8 (small outline integrated circuit) package for compact PCB designs.
* Low Power Consumption: Efficient design minimizes power dissipation in voltage reference circuits.

Package and Mechanical Details

* Package Type: SOIC-8 surface-mount package
* Pin Count: 8 pins
* Package Dimensions: Approximately 5.0 mm × 4.9 mm body size
* Mounting Style: Surface-mount technology (SMT)
* Operating Temperature Range: –40 °C to +125 °C industrial grade

Electrical Characteristics

| Parameter | Typical Value | Conditions |
| ---------------------------------- | ------------------ | -------------------------------- |
| Reference Voltage (Vref) | 2.495 V to 2.505 V | At 25 °C, Iref = 10 mA |
| Voltage Adjust Range | 2.5 V to 36 V | Set by external resistor network |
| Operating Current Range (Iref) | 1 mA to 100 mA | Continuous operation |
| Dynamic Impedance (Zdynamic) | 0.2 Ω (typical) | Iref = 10 mA |
| Input Voltage Range (Vin) | Up to 36 V | Maximum rating |
| Line Regulation | 0.01% / V | Change in Vin |
| Temperature Coefficient | 50 ppm/°C | Full operating temperature range |
| Output Noise Voltage | 60 µVrms | 10 Hz to 10 kHz bandwidth |
| Thermal Shutdown Threshold | ~150 °C | Device junction temperature |
| Supply Current (Iq) | 1 mA (typical) | Quiescent current |

Functional Description

The LM431CCMX operates as an adjustable shunt regulator with an internal bandgap voltage reference of approximately 2.5 V. It maintains a constant voltage between the reference pin and the cathode terminal by adjusting its internal transistor conduction. The output voltage can be set above the reference voltage by using an external resistor divider connected between the output, the reference pin, and ground.

When the voltage at the reference pin exceeds the internal bandgap reference, the device conducts more current to maintain the voltage at the programmed setpoint. This action allows the device to regulate output voltages with high precision and low noise.

Because it operates as a shunt regulator, the LM431CCMX must be connected in parallel with the load, drawing sufficient current to maintain regulation but not exceeding maximum current ratings.

Typical Applications

* Adjustable power supplies and voltage regulators
* Voltage monitoring and threshold detection circuits
* Switching power supply feedback control
* Battery chargers and battery management systems
* Precision voltage references for analog-to-digital converters (ADCs)
* Industrial instrumentation and measurement equipment
* Automotive electronics requiring stable voltage references
* LED driver voltage regulation

Design and Usage Recommendations

* Resistor Selection: Use high-precision, low-temperature coefficient resistors to set the output voltage accurately.
* Operating Current: Ensure the device current remains within specified limits for stable operation.
* Thermal Management: Proper PCB layout and copper area help dissipate heat generated during operation, especially at higher current levels.
* Noise Reduction: Place a small ceramic capacitor at the reference pin to ground to minimize noise.
* Input Voltage: Keep the supply voltage below the absolute maximum rating of 36 V for device reliability.
* Startup Behavior: The device starts regulating when the input voltage and current exceed the minimum thresholds.

Advantages

* High accuracy and low drift allow precise voltage regulation.
* Adjustable output voltage offers flexibility for a wide range of applications.
* Low dynamic impedance improves load and line regulation.
* Compact SOIC-8 package enables integration into dense circuit boards.
* Built-in thermal protection enhances device reliability.

Conclusion

The onsemi LM431CCMX is a versatile, high-precision adjustable shunt voltage regulator ideal for applications demanding stable and accurate voltage references. Its combination of wide operating voltage range, low noise, excellent temperature stability, and integrated protection features makes it an excellent choice for power supplies, instrumentation, and industrial control systems requiring dependable voltage regulation and monitoring.