Electronic cigarette application design based on core sea CSU8RP3125

With the increase in smoking bans in public places in the country and the expectation of healthy lifestyles, more and more old smokers have chosen to quit smoking, and the emergence of electronic cigarettes has given hope to old smokers to quit smoking. This paper introduces the core technology CSU8RP3125 CSU8RP3125 solution for electronic cigarettes, which can accurately monitor the battery voltage, prevent battery overcharge or undervoltage, measure the atomization current and prevent atomization and overcurrent. The smoke meets the match and is destined to be hurt! We all know that smoking is harmful to health, but we all have one foot on the mire, and we are still unable to extricate ourselves. In the era of increasing smoking cessation awareness, e-cigarettes stand out among various cigarette substitutes with high performance, high quality and high market competitiveness, bringing huge economic benefits and reducing the harm caused by second-hand smoke to people around them. .

Electronic cigarettes, also known as virtual cigarettes and electronic atomizers, are mainly used to quit smoking and replace cigarettes. It has the same appearance as a cigarette, a taste similar to that of a cigarette, and even more than the taste of a typical cigarette. It can also smoke and absorb the taste and feel like a cigarette. The electronic cigarette consists of a lithium-ion battery, an atomizer and a cartridge, and the liquid containing the nicotine component is misted through the atomizer, and is directly inhaled but does not generate smoke during the process.

Electronic cigarette solution based on core sea CSU8RP3125

This paper introduces the core technology CSU8RP3125 of the core technology Co., Ltd. application on the electronic cigarette, the program uses the built-in ± 1% precision 16MHZ high-speed PWM clock source, flexible control of LED breathing lights in a wide frequency range The internal reference source of the high-precision ADC with built-in 12-bit 1% measurement error is used to accurately monitor the battery voltage, prevent overcharge or undervoltage of the battery, measure the atomization current, and prevent atomization and overcurrent. .

system design

The electronic cigarette is composed of the main control chip CSU8RP3125, battery, button, LED breathing lamp and atomizer (see the figure below).

detailed design

1, short circuit protection

The low-voltage reset function of the chip itself is used to realize the short-circuit protection of the electronic cigarette, and the LVR of the chip is set at 2.4V. When the load terminal is short-circuited, the VDD pin of the chip is instantaneously pulled down to 2.4V, and the chip is reset, NMOS.

The control pin of the tube returns to the state of power-on reset, that is, the low level cuts off the NMOS to protect the MOS transistor.

2, overcharge protection

Since the battery is directly connected to the VDD of the chip, the internal reference voltage of the chip is used as an input, and VDD is used as a reference. Since the internal reference voltage is fixed, as long as the voltage on VDD changes, the AD value obtained will also be used. There is a corresponding change, using the AD value to calculate the voltage at the battery end. When the chip detects that the battery voltage is higher than 4.2V, let the NMOS control pin output a low level to turn off the NMOS to cut off the charging circuit between the charging terminal and the battery. To prevent overcharging of the battery. The CSU8RP3215 chip uses an internal reference to measure the battery voltage, eliminating the need for an external reference source and saving voltage divider resistors.

3, low voltage alarm

Use the same ADC detection method in section 2.2 to detect the VDD voltage (ie battery voltage). When the battery voltage is lower than 3.2V, let the NMOS transistor control pin output low level to turn off the NMOS and drive the LED to breathe by controlling the PWM output. A light to remind the user that the battery voltage is too low.

4, atomization overcurrent protection

The external AD channel is used to detect the voltage drop of the NMOS tube to the ground to convert the current flowing through the atomizer. Once the atomization current is detected to be too large, the chip will lower the control pin of the NMOS transistor to turn off the NMOS transistor. To prevent atomization and overcurrent. The CSU8RP3125's AD detects small signal accuracy and can be used for the reliability of electronic cigarette products.

5, control of breathing lights

Using the PWM output function of the chip itself, in the process from the off to the brightest of the LED lamp, when the PWM period is fixed, the PWM starts from the low level and increments a positive broadband every 3ms until the PWM output is high. On the contrary, in the process from the brightest to the off, the PWM starts from the high level, and increments a negative broadband every 6ms until the PWM output is low, which realizes the control of the breathing lamp. When the battery voltage is under voltage, the gradual speed of the breathing light will become 1/3 of normal operation, which reminds the user that it needs to be charged in time.

At present, the electronic cigarette is mainly targeted at the European and American markets, and the ESD (chip-scale) HBM model of the core CSU8RP3125 chip selected for this design is 8KV, and the operating temperature range is -40 to 85 °C. The high-speed PWM of the tested chip is stable, the ADC sampling effect is good, the temperature drift is small, and the performance is reliable. This type of chip is MSOP-8 package, which is conducive to PCB area reduction, and is very suitable for the development of electronic cigarettes.