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How to choose chips?

chipmall.com | 16/09/2020

Abstract: In the process of electronic research and development, we often face a situation that the product needs more functions, so we have to choose a newer version of the chip. During the evaluation process, we often faced with a variety of chips to choose from. How to choose the most suitable chip becomes especially important at this time. So how to make a correct judgment? Below, chipmall.com will give you a detailed answer.
1. Choose a chip in the mature stage.
1.1 Because the product is in the mature stage, the quality is relatively stable and reliable.

1.2 There are many existing materials and reference designs, which are easy to use.

1.3 You can't just look at the datasheet to see if the new features of the product can be realized, but also look at the user guide and errata. For example, if you want to use the USB function for a lumen chip, 　 need two additional IO ports as the configuration pins of the host/device, which cannot be fully controlled by the software. In addition, you also need to check which conditions the chip meets, civilian grade or Industrial grade, do you need special electrostatic protection, for example, several IO ports of lumens need special protection (indicated in errata).

1.4 Products in the mature stage are relatively reliable in supply. The production cycle of a large manufacturer generally takes several years. Even if it is no longer in production, there will be an upgraded version of PIN TO PIN.

1.5 Choose products from larger companies, and there are many reference materials. The reason why this article is ranked last is that the unit price of some products of large companies is more expensive than that of small companies.

2. To meet the functions of the existing design.
2.1 The appropriate chip should be selected according to the function of the product. Don't just focus on the main function or the new function, check whether all the functions are in compliance. Often large functions are compliant, but some small functions are not, causing waste. Take our products as an example: our meters are equipped with LED/LCD display, RS485 communication, fan PWM control, I2C communication, UART communication, key scanning,Buzzer PWM control, RTC, heartbeat detection, ADC detection, etc., RPM capture.

2.1.1 LED/LCD display: Which interface is used, such as SPI, IO port simulation, etc. If you can use SPI, etc., you need to consider how many channels of SPI of the chip are in total and whether it meets the number of SPI channels of the most complex system.

2.1.2 RS485 communication: What kind of interface is used, such as UART or others. If you use UART, you need to consider how many independent UARTs are needed in the most complex system, and whether the chip is compatible.

2.1.3 Fan PWM control:

2.1.3.1 Consider whether the chip has PWM function.

2.1.3.2 Consider that the most complex system requires several PWM output functions. See if the chip meets.

2.1.3.3 Consider whether the PWM output meets the existing functions. For example, duty cycle, period. Lumen timer PWM does not support prescaler.

2.1.4 RTC: Consider whether the chip has its own RTC function. If it comes with RTC function, you need to consider how the chip's RTC software and hardware work, whether there is a data retention function, and enter the RTC . What is the power consumption after mode. After all, low power consumption requires consideration of how long the battery can work.

2.1.5 Heartbeat: Since the IO port interrupt function is adopted, it is necessary to consider whether the chip supports the IO port interrupt, and what kind of interrupt (rising edge/falling edge/level) the IO port supports. and It is necessary to consider whether the number of IO port interrupts is sufficient in the most complex system.

2.1.6 ADC: Consider whether it has ADC function, as well as ADC conversion rate and ADC accuracy. And it is necessary to consider whether the reference power of the chip ADC is generated internally, if it is generated internally,It depends on whether the internal reference power supply can be input to the outside through the IO port, because if the voltage of the reference power supply is inconsistent with the chip supply voltage, and then due to accuracy requirements, if full scale is required, then it needs to be made externally. The reference power supply of the same voltage. Luminous ADC has its own internal reference voltage, but it does not provide external output.

2.1.7 Capture: Consider whether the capture function is suitable. Capture the number of bits of the timer, whether the input clock source can be divided, and whether the timer overflow can be interrupted.

3. Consider the difficulty and cost of building a software and hardware platform.

3.1 Consider whether the chip has an emulation and debugging interface, what tool is used for emulation, and whether it is compatible with the company’s existing debugging tools.

3.2 Consider what software is the software development environment of the chip, such as IAR. Of course, it is best if it is compatible with the company's existing development software, so as to minimize the development cycle and difficulty.