NXP SE95超高精度数字温度测量方案

NXP公司的SE95是超高精度数字温度传感器和热看门狗,采用能带隙温度传感器和Sigma Delta ADC技术,并提供超温检测输出.电源电压从2.8V到5.5V,关断模式电流为7.0uA,I2C总线接口到400kHz,温度范围从-55度C到125度C,温度分辨率为0.03125度C,-25度C到+100度C的温度精度为+/-1度C,主要可用于系统热管理,个人计算机,电子设备和工业控制器.本文介绍了SE95的主要特性,方框图和典型应用电路.

SE95:

Ultra high accuracy digital temperature sensor and thermal watchdog

The SE95 is a temperature-to-digital converter using an on-chip band gap temperature sensor and Sigma Delta analog-to-digital conversion technique. The device is also a thermal detector providing an overtemperature detection output.

The SE95 contains a number of data registers accessed by a controller via the 2-wire serial I2C-bus interface:

Configuration register (Conf) to store the device settings such as sampling rate, device operation mode, OS operation mode, OS polarity, and OS fault queue

Temperature register (Temp) to store the digital Temp reading

Set-point registers (Tos and Thyst) to store programmable overtemperature shutdown and hysteresis limits

Identification register (ID) to store manufacturer numbers

The device includes an open-drain output (pin OS) which becomes active when the temperature exceeds the programmed limits. There are three selectable logic address pins (pins A2 to A0) so that eight devices can be connected on the same bus without address conflict.

The SE95 can be configured for different operation conditions. It can be set in normal mode to periodically monitor the ambient temperature, or in shutdown mode to minimize power consumption. The OS output operates in either of two selectable modes: OS comparator mode and OS interrupt mode. Its active state can be selected as either HIGH or LOW. The fault queue that defines the number of consecutive faults in order to activate the OS output is programmable as well as the set-point limits.

The temperature register always stores a 13-bit two’s complement data giving a temperature resolution of 0.03125 degree C. This high temperature resolution is particularly useful in applications of measuring precisely the thermal drift or runaway. For normal operation and compatibility with the LM75A, only the 11 MSBs are read, with a resolution of 0.125 degree C to provide the accuracies specified. To be compatible with the LM75, read only the 9 MSBs.

The device is powered-up in normal operation mode with the OS in comparator mode,temperature threshold of 80 degree C and hysteresis of 75 degree C, so that it can be used as a stand-alone thermostat with those pre-defined temperature set points. The conversion rate is programmable, with a default of 10 conversions/s.

SE95主要特性:

Pin-for-pin replacement for industry standard LM75/LM75A

Specification of a single part over supply voltage from 2.8 V to 5.5 V

Small 8-pin package types: SO8 and TSSOP8 (MSOP8)

I2C-bus interface to 400 kHz with up to 8 devices on the same bus

Supply voltage from 2.8 V to 5.5 V

Temperature range from- 55 degree C to +125 degree C

13-bit ADC that offers a temperature resolution of 0.03125 degree C

Temperature accuracy of +/-1 degree C from- 25 degree C to +100 degree C

Programmable temperature threshold and hysteresis set points

Supply current of 7.0 uA in shutdown mode for power conservation

Stand-alone operation as thermostat at power-up

ESD protection exceeds 1000 V for Human Body Model (HBM) per JESD22-A114 and 150 V for Machine Model (MM) per JESD22-A115

Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

SE95应用:

System thermal management

Personal computers

Electronics equipment

Industrial controllers



图1.SE95方框图



图2.SE95典型应用电路