Power IC Selection Guide

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Power IC Selection Guide

Selecting a power IC is not only about meeting the performance requirements and reliability of the circuit, but also considering its size, weight, battery life and cost. Here are some basic principles for selection for reference.

1, priority to boost DC / DC converter

The use of a step-up DC/DC converter is not only efficient but also reduces the number of batteries (reducing the overall power supply volume and weight). For example, the MAX1674/1675 high-efficiency, low-power step-up DC/DC converter IC has a quiescent current of only 16μA, an efficiency of 94% at 200mA output, and a power consumption of only 0.1μA when the power is turned off. Limit to reduce the ripple voltage.

2, the best conditions for using LDO

When the ripple and noise in the output voltage are required to be extremely small, the input-output voltage difference is not large, and the micro-power, low-dropout (LDO) linear regulator is most suitable when the output current is not more than 100mA. For example, using a 3-cell NiCd, Ni-MH battery or a 1-cell lithium-ion battery, the output is 3.0-3.3V, and the operating current is less than 100mA. The battery life is longer and the efficiency is higher. For example, the ultra-micropower linear regulator BAW03A ~ 06A, its quiescent current is only 1.1μA, the output voltage is 1.2, 1.3, 1.4, 1.5, 1.7, 1.8, 2, 2.1, 2.3, 2.5, 2.7, .28, 2.9 3.0, 3.1, 3.2, 3.3, 3.4, 4.0, 4.2, 4.3, 4.5, 5.0, 5.8, 6.0V, available for user selection, output current 30mA ~ 50mA. The MAX8867/8868 has an output noise of 30μVrms. Another low-power, low-dropout LDO device, the GMT7250, has a quiescent current of 180μA and a dropout of less than 85mV at 100mA. The device has good temperature stability, typically 31ppm/°C, and has power supply status signal output and power-off control. The device has fixed voltage output: 3.3V, 4.85V, 5.0V, and can be connected with two resistors to set the output voltage. The output voltage range is 1.2~9.75V, and the output current can reach 250mA, which is suitable for most portable applications. .

3, when you need a negative power supply, try to use a charge pump

A portable power supply often requires a negative power supply. Since the required current is not large, the charge pump IC is the simplest to form a voltage inversion circuit. If the noise is required to be small or the output regulation is required, a charge pump IC with an LDO linear regulator can be used. . For example, MAX1680/1681, the output current can reach 125mA, adopt 1MHz switching frequency, only need to connect two 1μF small capacitors, the output impedance is 3.5Ω, there is power off control (power consumption is only 1μA when off), and can form a voltage doubler circuit. . Another MAX372, charge pump IC with regulated output, has adjustable output (0~-2×VIN), two external 0.1μF capacitors, consumes 35μA supply current, can output 30mA regulated current, and has power off control. Function (power consumption is only 0.1μA when off), small size μMAX package.

4. Do not pursue the latest devices with high precision and full functionality.

The accuracy of the power IC is generally ±2% to ±4%, and the accuracy is as high as ±0.5% to ±1%. The appropriate accuracy should be selected according to the requirements of the circuit, which can reduce the production cost. More versatile devices are more expensive, so there is no need to turn off the power function or there is no microprocessor (μP) or microcontroller (μC) in the product, so there is no need to select a device with a power-off function or an output power supply status signal. Not only can the cost be reduced, but the size is smaller.

5, do not "big horse car"