LH32M0SXX - single chip solution of pressure transmitter, temperature measurement and weighing

Structure Diagram of MarsMCU 

Mars-based Pressure Transmitter Solution
Pressure sensor is one of the most commonly used sensors in industrial practice and instrument control, and it is widely used in various industrial automatic control environments. The share of pressure sensor in the global overall sensor market is about 21%, second only to the flow sensor, and it is the second largest type of sensor product. It involves water conservancy and hydropower, railway transportation, automatic production control, aerospace, military industry, petrochemical industry, oil well, electric power, ship, machine tool, pipeline, etc.

The conventional acquisition pressure sensor solution is as follows:

Legendsemi has introduced a simpler solution for the acquisition pressure sensor as follows:

LM32M0SXX can collect up to 8 pressure sensing signals. It greatly simplifies the customer’s design and improves the cost performance and stability of the product.


Mars-based Infrared Temperature Measurement Solution

All medical products have become hot due to the COVID-19 pandemic. All kinds of non-contact infrared body thermometers have also become the hot-sale products for epidemic prevention and control.


(Infrared Temperature Measurement Equipment)

The basic principle of infrared temperature measurement is that since all objects exceeding absolute zero will send infrared rays, the special infrared camera sensor (infrared sensor stack) is selected to collect infrared rays sent by objects and convert them into weak uV~mV level working voltage data signals, which are then enlarged through the multiplied working voltage and transmitted into the high-precision AD converter, and the obtained digital signals are arithmetically calculated by single chip microcomputer to get specific temperature, which can be displayed by the industrial touch screen of human-machine interface or voice output or transmitted to the computer through data information transmission for centralized transportation.


The working principle diagram of the traditional solution is as follows:


LM32M0SXX infrared body temperature measurement solution of Legendsemi helps customers realize single chip solution:

The fully integrated SoC solution can save peripheral analog devices for customers, improve measurement precision and greatly improve the cost performance of the overall solution for customers.


Mars-based Electronic Scale Weighing Solution
The development trend of scale is the high precision and low cost, which puts forward higher requirements for high performance signal processing.
The best-selected ADC architecture for scale design is the Sigma-DeltaADC because of its low noise and high linearity at low update rates.
For scale system, the most important parameter indicators are the inner code, dynamic input range of ADC, noise-free resolution, conversion rate, system gain, temperature drift, etc.

Internal code:
The display resolution of the scale is from 1:3000 at the low end to 1:10000 at the high end. For example, for a scale with a full range of 5kg and an output display of 10000 codes, its resolution is 0.5g, which is displayed on LCD as the outer code. In order to guarantee the precision of outer code, a higher order of magnitude of the inner code is usually required as a guarantee. For example, some standard scales require an outer code with an inner code of 20 times, thus requiring an inner code resolution of 1:200000.

ADC dynamic range:
The figure below shows a circuit solution of typical scale. When the full-range output of the sensor is 5mV and the gain is set to 128, the input range of ADC is 640mV. If the reference voltage is 2.5V, this means that only about 2/5 of the dynamic range of ADC can be used. If 1:200000 inner code should be reached for 640mV, ADC needs to achieve a resolution of 1:781250 and a 19-20-bit precision.

Circuit solution of typical scale:

Temperature drift:
The maximum operating temperature range of the scale is generally -10°C to 50°C, and a 20-bit system with a gain error of 1ppm/°C will produce an error of 50LSB in the range of 50°C. Therefore, choosing an ADC with low gain temperature drift is also critical.

Noise-free resolution:
For scale applications, the most important parameter is the peak-to-peak noise or bit noise-free resolution. RMS noise multiplied by 6.6 times is the peak-to-peak noise.

Conversion rate:
The conversion rate is also an important parameter of system precision. For example, the peak-to-peak resolution of ADC with a 4Hz conversion rate can reach 20.5 bits, and the peak-to-peak resolution can reach only 16 bits after increasing the rate to 500Hz. Therefore, in the scale application, it is necessary to balance the two contradictory parameters of conversion rate and precision.
LH32M0SXX series of microcontroller of Suzhou Legendsemi Technology Co., Ltd. features the high performance 32-bit ARM®Cortex®-M0 cores, embedded in up to 128K bytes FLASH and 4K bytes SRAM, integrated with a high precision 24-bit Sigma-Delta analog-to-digital converter (ADC) and a front low noise programmable amplifier (PGA). It is an MCU that is suitable for scale applications.

Mars-based Scale Circuit Solution:

LH32M0SXXADC effective number of bits

In addition, “MARS” can also be used in environmental measurement, industrial measurement, fire protection, health care and other fields.


Evaluation board

The 48-pin and 24-pin evaluation boards, matching circuit diagrams and reference codes are available for rapid development by customers. The compiling environment supports IAR and KEIL. All routines IAR and KEIL are configured by default, and the customers can compile and burn only by opening them directly in the corresponding compiling environment.


Mars evaluation board based on different packages
(Left one: 48-pin package, right one: 24-pin package)


Mars product performance

32 位 ARM® Cortex® -M0 CPU
Up to 32 MHz operating frequency

Maximum 128K bytes FLASH memory
4 Kbytes SRAM

Clock module
Internal 32MHz RC oscillator (HRC) with typical precision of ±1%
Internal 32KHzRC oscillator (LRC) with typical precision of ±10%
32.768KHz low speed crystal oscillator (LXT)

Working environment
VDD voltage: 2.2~3.6V
VDDA voltage: 2.2~3.6V
Temperature range: 40~105℃

Power management
Low power modes: sleep, deep sleep and power-down modes
Support power-on/power-down reset (POR/PDR)
Support low voltage detection (LVD)

General purpose IO
35 I/Os support up to 32MHz operating frequencies
Support interrupt vector

High precision analog-to-digital converter (Sigma-Delta ADC)
24-bit high precision Sigma-Delta ADC
Support up to 8 external input channels
Support single-ended, differential inputs
1/2/4/8/16/32/64/128 times selectable gain
Integral non-linearity (INL) typical value 5ppm
ADC channel temperature drift 2ppm/℃
Output rate 8Hz~8kHz
- ENOB≥19.5bit@30sps,PGA=128
- ENOB≥15.4 bit@8ksps,PGA=128
Hardware automatically switches ADC channels, automatically polls to read ADC data and interrupts the notification of MCU or DMA.
With reference voltage, output 1.8/2.35/2.45/2.8V optional
Integrated temperature sensor/supply voltage detection channel

Digital comparator
Fast response digital comparator

LCD Driver
Integrated 4COM, 20SEG configuration
Integrated charge pump

LED Driver
Support 7 x 8 segments at a maximum

One-circuit buzzer
2 timers
4-circuit 16-bit advanced control timer (TIM1) with 6-channel PWM output for dead zone and complementary control
4-circuit 16-bit general timer (TIM2) with PWM output

Programmable constant current source
Support PWM control

OLED color screen DMA acceleration module
Serial single wire debugging (SWD)

Package and Ordering


North/East China
Tel.: 15062630141

Southern China
Tel.: 13606907992

Address: Room 1306, Zhongkun Building, Haidian District, Beijing