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DS2422S Datasheet(PDF) 6 Page - Dallas Semiconductor |
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DS2422S Datasheet(HTML) 6 Page - Dallas Semiconductor |
6 / 48 page DS2422 6 of 48 PIN DESCRIPTION PIN NAME FUNCTION 1 VPAD Operating voltage of the serial interface pads CNVST, SCLK, SDATA. Used for level translation from the VBAT-powered internal logic to the 5V-powered ADC. Connect to VBAT if the serial interface is not used. 2SCLK Serial clock signal for serial interface. May connect directly to the corresponding MAX1086 pin. The idle state for the pin is low. 3SDATA Serial data pin for the serial interface. May connect directly to the DOUT pin of MAX1086. The pin includes a weak pulldown and therefore has an idle state of low. 4 CNVST Conversion Start control signal for the MAX1086. The idle state for the pin is low. 9 AGND Analog ground. Ground reference for external ADC and charge pump. 10 X1 First of two crystal pins for the real time clock crystal. A standard 6pF 32KHz crystal is used. The accuracy of the device's real time clock is largely dependent on the temperature characteristics of the crystal. Trace length from the device to the crystal should be minimized to reduce their capacitive effect. 11 ALARM Logic open-drain output with 215 W maximum on-resistance, operating range 0V to 5.25V. Power-on default is OFF. 12 X2 Second of two crystal pins for the real time clock crystal. 13 IO 1-Wire communication line, data input and output. This pin also charges the internal parasitic power cap that allows the 1-Wire front end of the device to run without VBAT supply. 14 GND Common ground supply for the device and VBAT. 16 TEST_SPLY Connect to GND (test pin) 21 TEST_RX Connect to GND (test pin) 22 PUMP_ONZ Signal to control an external charge-pump. The signal polarity is designed to fit to the MAX619 charge pump/regulator. 23 VBAT 3V power supply for the device, typically a battery. This pin supplies power to all parts of the device except for the 1-Wire front end. 24 TEST_CG Do not connect (test pin) 9 pins NC Not connected DESCRIPTION The DS2422 temperature/data logger combines the core functions of a fully featured data logger in a single chip. It includes a temperature sensor, RTC, memory, 1-Wire interface, and serial interface for an analog-to-digital converter (ADC) as well as control circuitry for a charge pump. The ADC and the charge pump are peripherals that can be added to build application-specific data loggers. Without external ADC, the DS2422 functions as a temperature logger only. The DS2422 measures the temperature and/or reads the ADC at a user-defined rate. A total of 8192 8-bit readings or 4096 16-bit readings taken at equidistant intervals ranging from 1 second to 273 hours can be stored. In addition to this, there are 512 bytes of SRAM for storing application specific information and 64 bytes for calibration data. A mission to collect data can be programmed to begin immediately, after a user- defined delay, or after a temperature alarm. Access to the memory and control functions can be password- protected. The DS2422 is configured and communicates with a host computing device through the serial 1-Wire protocol, which requires only a single data lead and a ground return. Every DS2422 is factory-lasered with a guaranteed unique 64-bit registration number that allows for absolute traceability. The extremely low energy con- sumption in conjunction with its high level of programmability makes the DS2422 the ideal choice for low-cost data loggers that can take millions of measurements from the energy of a single 3V button cell. APPLICATION The DS2422 allows the design of data loggers or monitors with a minimum number of components. The simple circuit of Figure 1 can monitor body or room temperature with 0.0625°C resolution. For very high temperature- monitoring applications, a thermocouple can be connected to the analog-to-digital converter (ADC) through a pre- amplifier, as shown in Figure 2. The internal temperature sensor of the DS2422 keeps track of the reference temperature, which is needed to accurately convert the voltage reading of the thermocouple into the actual temperature of the monitored object. A less obvious application of the DS2422 is inside of major equipment. Besides the temperature inside the chassis, the serial interface can monitor up to 16 digital signals, which are parallel-clocked into an external shift register by CNVST and then shifted into the DS2422 through the SDATA pin |
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Similar Description - DS2422S |
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