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MAX1619 Datasheet(PDF) 6 Page - Maxim Integrated Products |
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MAX1619 Datasheet(HTML) 6 Page - Maxim Integrated Products |
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Remote/Local Temperature Sensor with Dual- Alarm Outputs and SMBus Serial Interface 6 _______________________________________________________________________________________ Pin Description Detailed Description The MAX1619 is a temperature sensor designed to work in conjunction with an external microcontroller (µC) or other intelligence in thermostatic, process-control, or monitoring applications. The µC is typically a power- management or keyboard controller, generating SMBus serial commands either by “bit-banging” general-pur- pose input/output (GPIO) pins or through a dedicated SMBus interface block. Essentially an 8-bit serial analog-to-digital converter (ADC) with a sophisticated front end, the MAX1619 contains a switched current source, a multiplexer, an ADC, an SMBus interface, and associated control logic (Figure 1). Temperature data from the ADC is loaded into two data registers (local and remote). The remote temperature data is automatically compared with data previously stored in four temperature-alarm threshold registers. One pair of alarm-threshold registers is used to provide hysteretic fan control; the other pair is used for alarm interrupt. The local temperature data is avail- able for monitoring. ADC and Multiplexer The ADC is an averaging type that integrates over a 60ms period (each channel, typical) with excellent noise rejection. The multiplexer automatically steers bias currents through the remote and local diodes, measures their forward voltages, and computes their temperatures. Both channels are automatically converted once the conversion process has started, either in free-running or single-shot mode. If one of the two channels is not used, the device still performs both measurements, and the user can simply ignore the results of the unused channel. The DXN input is biased at 0.65V above ground by an internal diode to set up the analog-to-digital (A/D) inputs for a differential measurement. The worst-case DXP–DXN differential input voltage range is 0.25V to 0.95V. Excess resistance in series with the remote diode caus- es about +1/2°C error per ohm. Likewise, 200µV of off- set voltage forced on DXP–DXN causes about 1°C error. SMBus Serial-Data Input/Output, Open Drain SMBDATA 12 SMBus Serial-Clock Input SMBCLK 14 Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode. Low = standby mode, high = operate mode. STBY 15 SMBus Address Select Pin (Table 8). ADD0 and ADD1 are sampled upon power-up. Excess capacitance (>50pF) at the address pins when floating may cause address-recognition problems. ADD1 6 Ground GND 7, 8 SMBus Slave Address Select Pin ADD0 10 SMBus Alert (interrupt) Output, Open Drain ALERT 11 Combined Current Sink and A/D Negative Input. DXN is normally internally biased to a diode voltage above ground. DXN 4 Combined Current Source and A/D Positive Input for Remote-Diode Channel. Do not leave DXP floating; connect DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for noise filtering. DXP 3 PIN Supply Voltage Input, 3V to 5.5V. Bypass to GND with a 0.1µF capacitor. A 200 Ω series resistor is recom- mended but not required for additional noise filtering. VCC 1 FUNCTION NAME Overtemperature Alarm Output, Open Drain. This is an unlatched alarm output that responds only to the remote diode temperature. OVERT 9 Not internally connected. Connect to GND to act against leakage paths from VCC to DXP. GND 2 No Connection. Not internally connected. May be used for PC board trace routing. N.C. 5, 13, 16 |
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