This device is specifically designed for eight-electrode AC Body Fat Scale applications. Measuring body fat uses a technique whereby an AC current flowing through the human body is measured and then used to calculate a body fat value. The specialised circuits to do this are a weight measurement circuit and a fat measurement circuit. The weight measurement circuit uses an external load cell to output a signal, which after amplification by an operational amplifier, and then conversion using an A/D converter, reads the corresponding value as the calculated weight. The fat measurement circuit uses an AC signal via an electrode slice to flow through human body. After amplification by an internal operational amplifier, and then conversion by an A/D converter, the measured value is one representing body impedance, which is used to calculate the corresponding body fat value.

This device is a Flash Memory A/D type 8-bit high performance RISC architecture microcontroller which includes a multi-channel 24-bit Delta Sigma A/D converter, designed for applications that interface directly to analog signals and which require a low noise and high accuracy analog-to-digital converter. For memory features, the Flash Memory offers users the convenience of multi-programming features. Other memory includes an area of RAM Data Memory as well as an area of true EEPROM memory for storage of non-volatile data such as serial numbers, calibration data etc.

Analog features include a multi-channel 24-bit Delta Sigma A/D converter and other circuitry specifically designed for Body Fat Scale applications. Multiple and extremely flexible Timer Module provides timing, pulse generation and PWM generation functions. Communication with the outside world is provided by including fully integrated SPI, I2C and UART interface functions, these popular interfaces which provide designers with a means of easy communication with external peripheral hardware. Protective features such as an internal Watchdog Timer, Low Voltage Reset and Low Voltage Detector coupled with excellent noise immunity and ESD protection ensure that reliable operation is maintained in hostile electrical environments.

A full choice of HIRC, LIRC and LXT oscillators functions are provided including two fully integrated system oscillators which require no external components for their implementation. The ability to operate and switch dynamically between a range of operating modes using different clock sources gives users the ability to optimise microcontroller operation and minimise power consumption.

The inclusion of flexible I/O programming features, Time-Base functions along with many other features ensure that only a minimum of external components is required for application implementation, resulting in reduced component costs and reductions in circuit board areas.

Features:

• operating voltage: fSYS =8MHz: 2.2V~5.5V
• up to 0.5μs instruction cycle with 8MHz system clock at VDD =5V
• power down and wake-up functions to reduce power consumption
• oscillator types:
  • internal high speed 8MHz RC – HIRC
  • internal low speed 32kHz RC – LIRC
  • external low speed 32.768kHz crystal – LXT
• multi-mode operation: FAST, SLOW, IDLE and SLEEP
• fully integrated internal oscillators require no external components
• all instructions executed in 1~3 instruction cycles
• table read instructions
• 115 powerful instructions
• 16-level subroutine nesting
• bit manipulation instruction

Peripheral Features

• flash program memory: 16K×16
• data memory: 1024×8
• true EEPROM memory: 1024×8
• in application programming – IAP
• watchdog timer function
• 26 bidirectional I/O lines
• programmable I/O port source current and sink current for LED driving applications
• two external interrupt lines shared with I/O pins
• multiple timer modules for time measure, input capture, compare match output, PWM output function or single pulse output function
• serial interface module – SIM includes SPI and I2C interfaces
• fully-duplex/half-duplex universal asynchronous receiver and transmitter interface – UART
• dual time-base functions for generation of fixed time interrupt signals
• 11 differential or 22 single-end channel 24-bit resolution Delta Sigma A/D converter
• internal LDO with bypass function for PGA, ADC and external sensor power supply
• body fat measurement circuit
• integrated 16-bit cyclic redundancy check function – CRC
• low voltage reset function
• low voltage detect function
• package type: 48-pin LQFP