Digital Temperature Monitor Max6622 Temperature Measurement And Control Applications

1 Introduction With computer performance innovation

, more and more functions are integrated into the computer. Therefore, increasing the capacity of the computer. To meet the needs of a large number of data processing, more and more integrated into the chipset host, CPU and chipset working frequency is also rising. More chipset and faster clock frequency will produce more heat. In the limited space. System heat dissipation is a difficult problem. How to balance system performance, the system of comfort (including computer case temperature, fan rotation noise), and the system running time, is an important topic of computer aided design, therefore, this paper based on the MAX6622's temperature measurement and control applications.

2 MAX6622 Description MAX6622 is a precision MAXIM company introduced multi-channel temperature monitor, internal integrated A / D converter, register, interface circuitry, can be directly output digital signals. The device has a high precision, fast response, small size, low power consumption and easy control software interface. Widely used in desktops, notebooks, servers, workstations and other temperature monitoring system.

MAX6622 precision multichannel temperature sensor to monitor the local temperature and 4-way remote temperature. All temperature channels have to set the alarm threshold. When the measured channel temperature exceeds the threshold, the corresponding state status register bit. Two open-drain output ALERT and OVERT, according to the state of the state register set corresponding bit low. 2-wire serial interface standard system management bus, write-byte executable, read byte, send byte and receive byte commands can also be used to read temperature data and set alarm thresholds. MAX6622 operating temperature range is -40 to +125 , 16-pin TSSOP package.

2.1 Features 2.2 Pin Configuration and Function Description

MAX6622 pin configuration shown in Figure 1, the pin function description see Table 1 below.

2.3 mode MAX6622 is a 5-channel precision temperature monitor, there is a local temperature sensor and 4 channel remote temperature sensor channels, each channel with a programmable temperature alarm thresholds, channel 1 and channel 4 also with programmable over-temperature threshold. Through the SMBus serial interface and a dedicated alarm output to achieve MAX6622 communication. ALERT and OVERT alarm output is more than software settings used to identify the temperature threshold. Typical applications for the interruption ALERT, OVERT connected to the fan, the system switches or other temperature control circuit.

2.3.1 ADC conversion mode

In the default conversion mode, MAX6622 first measurement channel 1, followed by measurement of channel 2, channel 3, the local channel, Channel 4, began to change. And conversion results are stored in the corresponding temperature data registers.

2.3.2 Low-power standby mode

By STOP bit configuration register 1 will place one into the software standby mode. STBY low to buy into the hardware standby mode. Software standby mode to ADC to stop working, and will reduce the supply current to about 30mA, the hardware interrupt ADC clock standby mode, supply current of about 350mA. In software or hardware standby mode, the data retained in memory, and the SMBus interface is active, listen to SMBus commands. If the SMBus start signal is identified, time-out interval is activated. Activation SMBus has caused supply current. If you are to receive back-order conversion, the conversion cycle is interrupted, and the temperature register is not updated, the previous data unchanged and can still be used.

2.3.3 ALERT interrupt mode

Internal or external temperature data when the maximum temperature limit is exceeded, resulting ALERT interrupt. ALERT is an open-drain output, multiple devices sharing a normal interrupt lines. All of the ALERT interrupt set register 3 through its shield.

2.3.4 OVERT over-temperature alarm

MAX6622 has two remote alarm threshold is used to store data over-temperature register, the over-temperature register is OVERT output. When the measured channel temperature is higher than the corresponding threshold temperature stored in registers, generate OVERT signal. An over-temperature output can be used to activate the cooling fan, send a warning to initialize the clock frequency down, or the system shut down to prevent destruction of components.

3 Typical Application Circuit Computer CPU heat source for the largest, in addition, graphics processor (GPU), DDR memory, hard drives and optical drives require temperature measurement and control components. Contained within these components used for remote temperature sensing diode, temperature sensor can directly detect internal CPU core temperature, and precisely control the temperature.

MAX6622 typical application circuit shown in Figure 2. Remote temperature measurement accuracy depends on the remote diode ideal factors. IC temperature of the bottom diode is usually PNP type, DXP_ must be connected to the emitter of the transistor, DXN_ be connected with the base. If the channel temperature does not use a road, then the road DXP_ and DXN_ vacant.

ADC has a good low-frequency signal inhibition. When the electromagnetic interference is large, the required connection between the DXP_ and DXN_ a 2200 pF capacitor, helps filter, but no more than 3 300pF, because the switching current rise time caused the error occurred.

4 Software Design First set configuration register, so MAX6622 work in normal mode. Register in the alarm threshold set temperature limit, when the measured temperature is higher than the corresponding threshold channel registers temperature, OVERT-bit enabled, used to activate the cooling fan, send a warning to initialize the clock, or the system shut down to prevent destruction of components. OVERT position has remained in effect until the temperature drops below the current limit has been set temperature minus the hysteresis value of 4 , so the ambient temperature will remain at the set temperature of the following. This work may be under the MAX6622 microprocessor from the system as a separate temperature monitor, automatic thermostat function. The main program flow shown in Figure 3.

Software design using C language programming, greatly improve the efficiency of development and debugging; the same time easy to understand documentation produced, easy to transplant. Using IAR C compiler environment provides integrated debugging environment and the C430 language Workbench C-SPY debugger compiled, downloaded directly to the on-chip Flash memory, offline operation. The user friendly interface, debugging the software can be seen in the upper register of the contents of all online, in favor of single-step operation, on-line real-time observation of the definition of the value of each variable. The following is part of the code.

5 Conclusion

Details

Digital Temperature Monitor Max6622 Temperature Measurement And Control Applications

By: hotxueboy

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