Maxim公司的MAX1441是接近式和觸摸傳感器IC,14V的工作電流只有100uA, 1.2fF LSB電容/數(shù)字分辨率,工作電壓5V-28V,45V過壓保護(hù),2k字閃存,128B SRAM,傳感器I/O線±2kV ESD保護(hù),JTAG接口,支持兩個單獨接地電容傳感器輸入.主要用在無源遙控鑰匙(PRKE)系統(tǒng)接近傳感和物件檢測系統(tǒng).本文介紹了MAX1441主要特性,方框圖, 典型應(yīng)用電路圖以及MAX1441評估板主要特性,電路圖,材料清單和PCB布局圖.
The MAX1441 proximity and touch sensor IC is designed for capacitive proximity sensing in automotive passive remote keyless entry (PRKE) and other applications. This device provides signal processing to support two independent touch/proximity sensor channels. The device features two open-drain output pins with high-voltage capability up to 28V, as well as five digital I/Os to indicate sensing events. During manufacturing, JTAG programming uses four digital I/Os.
The device uses grounded electrode capacitive sensing to measure capacitance between one of the two sense pins and the ground. A hand approaching a sense electrode attached to these sense pins causes a change in measured capacitance indicating the presence (touch or proximity) of the object. Active-guard outputs shield the sense electrode from unwanted sources without adding parasitic capacitance. Spread-spectrum techniques in the sensor excitation circuit reduce both electromagnetic emissions and susceptibility to interfering signals. In addition, the sensing excitation frequency is programmable from 100kHz to 500kHz in 10kHz steps to avoid interference.
The sensor input signals are converted to a 12-bit digital data and are available to an on-chip microcontroller (FC). The device provides independent offset compensation of up to 63pF for each input channel. Each channel can be programmed to 5pF, 10pF, or 20pF full-scale range.
The device features an internal MAXQ® microcontroller with 2kword of flash for user programs and 128 bytes of SRAM. This feature provides the ability to implement customized signal processing and discrimination algorithms that optimize performance in the systems.
The device offers user-configurable general-purpose digital I/O lines. Power-on-reset (POR) circuitry provides consistent startup of the device, and a watchdog timer ensures long-term reliable operation of the user’s software.
The device is available in a 20-pin TSSOP package and is specified over the -40NC to +105NC automotive temperature range.
MAX1441主要特性:
Low Average Operating Current (100μA at 14V)
1.2fF LSB Capacitance-to-Digital Resolution (5pF Range)
5V to 28V Operation
45V Overvoltage Protection
Sinusoidal Excitation for Reduced EMI Emissions
Frequency Spreading Operation for Reduced EMI Susceptibility and Emissions
Active-Guard-Sense Architecture Provides Increased Flexibility in System Packaging
CMOS/LVCMOS-Compatible Outputs
Embedded μC Supports User-Specified Adaptive Sense Algorithms
2kwords Flash Memory
128-Byte SRAM
±2kV ESD Immunity on Sensor I/O Lines
JTAG Serial Interface
Supports Two Independent Grounded Capacitor Sensor Inputs
-12V Reverse Voltage Protection with External Diode
MAX1441應(yīng)用:
PRKE System Proximity Sensing
Object Detection Systems
圖1. MAX1441方框圖
圖2. MAX1441典型應(yīng)用電路圖
MAX1441評估板
The MAX1441 evaluation system (EV system) provides a proven design to evaluate the MAX1441 capacitive proximity and touch sensor. The EV system consists of two PCBs. The MAX1441 evaluation kit (EV kit) includes the typical application circuit and all electronics for USB-to-JTAG communication between the on-board device and the PC. The MAX1441TP evaluation kit (TP EV kit) includes two touch pads. The TP EV kit connects to the EV kit through 20-pin right-angle connectors. The EV kit board connects to either the factory-provided kit touch pads board, or a custom user-supplied touch sensor. The EV system also includes Windows XPM- or Windows VistaM-compatible integrated development environment (MAX-IDE) for the MAXQM microcontroller core of the device.
The EV kit comes with a MAX1441GUP/V+ installed.
MAX1441評估板主要特性:
Wide 6V to 28V VBAT Supply Range
External Touch-Sense Pad Included
Adaptive Firmware Source Code Included
USB PC-to-JTAG Connection
USB Powered or Battery Powered
Compatible with the MAX-IDE Development Tool
Proven PCB Layout
Fully Assembled and Tested
圖3.MAX1441評估板電路圖(1)
圖4.MAX1441評估板電路圖(2)
圖5.MAX1441評估板電路圖(3)
圖6.MAX1441評估板電路圖(4)
圖7.MAX1441評估板電路圖(5)
圖8.MAX1441評估板電路圖(6)
MAX1441評估板材料廠清單:
圖9.MAX1441評估板PCB布局圖
詳情請見:
http://datasheets.maxim-ic.com/en/ds/MAX1441.pdf
和
http://datasheets.maxim-ic.com/en/ds/MAX1441EVSYS.pdf
