Reference scheme for selecting MSP430 peripheral component models
The MSP430 series microcontroller is a 16-bit ultra-low MSP430 single-chip microcomputer that Texas Instruments (TI) introduced to the market in 1996. It has a reduced power consumption and a Reduced Instruction Set (RISC) Mixed Signal Processor. This is called a mixed-signal processor because it addresses a number of different functional analog circuits, digital circuit modules, and microprocessors on a single chip to provide "single-chip microcomputer" solutions.
This series of microcontrollers are mostly used in portable instruments that require battery power. This article mainly explains the MSP430 series chip peripheral crystal design selection and precautions.
MSP430 series chip generally take two crystals outside: a frequency crystal, usually in the 4 ~ 16Mhz to choose; another clock crystal, namely 32.768Khz crystal, early selection of in-line package, and now most of the use of chip packaging One of the products is easy to mount, and the second is the pursuit of product stability and quality reliability. ---Application Circuit
chip peripheral crystal design selection and precautions.
---MSP430 Development Board
一、The choice of frequency crystal
Usually, the MSP430 chip's primary frequency crystal is generally chosen to be an integral multiple of 4Mhz, ie 4Mhz, 8Mhz, 16Mhz, 32Mhz, etc. In the early days of circuit design, 49S package products with lower cost were generally selected. At this stage, more and more stable, smaller, and easy-to-mount SMD 3225 package products, the DSX321G introduced by Japan KDS Vacuum Co., Ltd. DSX320G\\DSX320GE products.
1. DSX321G 8Mhz for Industrial and Consumer Products
The model product package is 3.2mm*2.5mm, the volume is less than 1/5 of the traditional in-line 49S package, the precision can reach 20PPM, the working temperature can reach -40-+85°C industrial grade, fully meet the customer's requirements. .
2. DSX320G/DSX320GE for automotive electronics and industrial control products
The package agreement for this model is 3.2*2.5mm, accuracy can be 100ppm and 50ppm, in addition to the temperature can meet the customer's requirements -40-+125 °C, -40-+150 °C, but also in line with AEC-Q200 standards.
二、The choice of 32.768Khz clock crystal
The 32.768Khz family has a lot of models, all kinds of in-line and patch, all kinds of load capacitance, various precision. According to MSP430 different series to do some targeted recommendations:
IC name Quartz crystal CL(pF)
MSP430F169 32.768kHz 12.5
MSP430F2131 32.768kHz 12.5
MSP430F2131 32.768kHz 6
MSP430F413 32.768kHz 12.5
MSP430F413 32.768kHz 6
MSP430FG4619 32.768kHz 12.5
MSP430FG4619 32.768kHz 6
MSP430F1232IPW 32.768kHz 12.5
MSP430F1XX 32.768kHz 12.5
MSP430F2XX 32.768kHz 12.5
MSP430F4XX 32.768kHz 12.5
MSP430F4XX 32.768kHz 12.5
MSP430F5XX 32.768kHz 12.5
MSP430FE427 32.768kHz 6
MSP430P325 32.768kHz 6
1, low load, low ESR value products:
In-line package DT-26 32.768Khz 20PPM 6PF
SMD package DMX-26S 32.768Khz 20PPM 6PF
SMD package NX3215SA 32.768Khz 20PPM 6PF
2, conventional load products:
In-line package DT-26 32.768Khz 20PPM 12.5PF
SMD package DMX-26S 32.768Khz 20PPM 12.5PF
SMD package NX3215SA 32.768Khz 20PPM 12.5PF
三、 with the MSP430 microcontroller 32.768Khz crystal (Cylindrical crystal as an example) principle, basic applications, use precautions
Cautions on the use of tuning fork crystal oscillator standard (32.768Khz cylindrical crystal)
1, impact resistance
If excessive impact is applied, it will cause deterioration or no vibration.
Take full care not to fall. In addition, use it as much as possible without impact.
When automatic welding or conditions change, fully confirm before use.
2, heat resistance, moisture resistance
Prolonged use and storage under high or low temperature or high humidity conditions can cause deterioration of the vibrator. Use and store as much as possible under normal temperature and humidity conditions.
3, solder heat resistance
The standard type vibrator uses a 178°C melting point solder. The temperature inside the vibrator exceeds 150°C, which may cause deterioration of the product characteristics or lack of vibration.
Whether to use heat-resistant products or SMD vibrators when assembling at conditions above the above temperature.
When using flow soldering, please confirm with your company or contact our company.
Welding conditions, lead part, less than 280°C for 5 seconds or less than 260°C for 10 seconds.
Also, do not solder directly at the root of the lead. It is the cause of the deterioration of the characteristics.
4, the printed circuit board assembly method
When the tuning fork-type vibrator is turned upside down, fully fix it to the circuit board. In particular, in the vibration area, as shown in the figure, the buffer material is placed between the circuit board and the vibrator, or it is fixed with an elastic agent (silica gel, etc.) with good elasticity. Also, avoid applying the adhesive to the base glass part.
When the vibrator is used upright, the vibrator is separated from the circuit board by DT-38 type 3mm or more and DT-26 type 2mm or more.
5, lead processing
When cutting the lead wire, the cutting blade must be fully prepared.
During lead processing or when the lead wire is bent, excessive force is applied to the root of the lead wire to cause cracks in the base glass, or excessive force is applied to the press-fitting section. In addition, the lead portion of the lead should be left with a straight lead portion of 0.5 mm or more.
6, ultrasonic cleaning and ultrasonic welding
Due to the resonance of the internal wafer, the cause of vibration is not generated. Therefore, it is not guaranteed whether ultrasonic welding can be performed.
About ultrasonic cleaning, please confirm with your company.
7, excitation standard
When the vibrator is used with excessive excitation standards, it may cause deterioration or no vibration.
For this type of vibrator, we recommend using it below 1.0μW. However, it is not guaranteed to use more than 2.0μW.