LM2940S-12/NOPB

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LM2940 is an adjustable voltage regulator IC introduced by Texas Instruments. It is an integrated linear voltage regulator circuit specifically designed to provide a cost-effective solution for low noise, low dropout and low power applications.

The LM2940S-12/NOPB is the model which features low dropout linear regulator with an adjustable output that can be set from 1.2V to 13.0V. It offers competitive performance in terms of noise, power consumption and output voltage accuracy. The additional features include a selectable output current limit, a thermal shutoff circuit and an enable pin. It has an operating temperature range of -40 to +125 degree Celsius.

Applications

The LM2940 is used in a wide variety of applications like mobile phones, battery powered devices, automotive power systems, networking systems, instrumentation and embedded systems. It can be used as a step-up regulator, step-down regulator, inverter and as a power source for low power circuits. It is a great selection for applications needing multiple output voltages and adjustable output control.

Features

• Adjustable output voltage (1.2V - 13.0V)
• Low noise (10 μVrms) output voltage
• Low dropout voltage (140 mV at 50mA load current)
• Low power consumption
• Selectable output current limit
• Thermal shutdown
• Enable pin for power saving
• Operating temperature range from -40 to +125 degree Celsius

Working principle

The LM2940S-12/NOPB utilizes a NPN transistor as a pass-control element. The output voltage can be adjusted by changing the value of an external resistor connected to the adjustment pin. The input and output voltages of the IC are relative to ground. The pass-transistor is activated and connected between the input and output when the voltage on the adjustment pin (VADJ) is higher than ground voltage.

The current flowing through the pass-transistor is controlled by an error amplifier (EA), which regulates the output voltage. The EA compares the voltage on the feedback pin (VEE) to the voltage on the VADJ pin in order to adjust the output voltage. When the internal reference voltage (VREF) is higher, the pass-transistor will be driven harder, which increases the output voltage. When the VREF voltage is lower, the pass-transistor will be driven less, thus reducing the output voltage.

The LM2940 also includes an enable pin (EN) that allows the user to enable or disable the power switch that controls the output voltage. The current limit and thermal shutdown protect are also included, which prevent the device from overloading itself. This prevents damage to the power supply and the attached components.

Conclusion

The LM2940S-12/NOPB is an adjustable low-noise, low-dropout and low-power linear voltage regulator IC from Texas Instruments. It has adjustable output voltage from 1.2V to 13.0V and features low noise and low power consumption. It is used in a variety of applications from mobile phones to instrumentation and embedded systems. It functions through a NPN transistor pass-control and error amplifier for the adjustment of output voltage. The additional features like selectable output current limit, thermal shutoff and enable pin ensure safety and reliability.

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