ver: 0.2 oct 02, 2008 tel: 886-3-5788833 http://www.gmt.com.tw 1 global mixed-mode technology inc. G784 1 c remote and local temperature sensor with smbus serial interface features ? two channels: measures both remote and local temperatures ? no calibration required ? built-in noise-buster for remote sensor ? smbus 2-wire serial interface ? programmable under/overtemperature alarms ? supports smbus alert response ? accuracy: 1 c (+60 c to +100 c, remote) 3 c (+60 c to + 100 c, local) ? 320 a (typ) average supply current during conversion ? +3v to +5.5v supply range ? small 8-lead sop , msop and tdfn package ? remote temperature measurment up to 160 c by using offset shifting method (see ? measure remote temperature higher than 127 c ? sec- tion) ? smbus inputs with built-in mos switch to pre- vent reverse current from bus to ic vcc applications desktop and notebook central office computers telecom equipment smart battery packs test and measurement lan servers multi-chip modules industrial controllers general description the G784 is a precise digital thermometer that reports the temperature of both a remote sensor and its own package. the remote sensor is a diode-connected tran- sistor typically a low-cost, easily mounted 2n3904 npn type that replace conventional thermistors or thermo- couples. remote accuracy is 1 c with no calibration needed. it also has a build-in noise filtering function in remote sensor measuring the diode temperature. the remote channel can also measure the die temperature of other ics, such as microprocessors, that contain an on-chip, diode-connected transistor. the 2-wire serial interface accepts standard system management bus (smbus) write byte, read byte, send byte, and receive byte commands to program the alarm thresholds and to read temperature data. the data format is 11bits plus sign, with each bit cor- responding to 0.125 c, in two ? s-complement format. measurements can be done automatically and autonomously, with the conversion rate programmed by the user or programmed to operate in a single-shot mode. the adjustable rate allows the user to control the supply current drain. the G784 and G784-1 have the same functions but different smbus slave addresses. this allows for one of each to be on the bus at the same time. the G784 is available in a small, 8-pin sop, msop and tdfn surface-mount package. pin configuration typical application circuit therm dxn 8 6 5 1 2 3 4 vcc dxp smbdata smbclk gnd sop-8/msop-8 G784/G784-1 7 alert 0.1 f 3v to 5.5v vcc dxp dxn smbclk smbdata alert 10k each clock data interrupt to c gnd 2200pf 2n3904 therm tdfn3x3-8 1 2 3 4 8 7 6 5 thermal pad G784/G784-1 note: recommend connecting the thermal pad to the gnd or let it keep floating. therm dxn vcc dxp smbdata smbclk gnd alert therm dxn 8 6 5 1 2 3 4 vcc dxp smbdata smbclk gnd sop-8/msop-8 G784/G784-1 7 alert 0.1 f 3v to 5.5v vcc dxp dxn smbclk smbdata alert 10k each clock data interrupt to c gnd 2200pf 2n3904 therm 0.1 f 3v to 5.5v vcc dxp dxn smbclk smbdata alert 10k each clock data interrupt to c gnd 2200pf 2n3904 therm tdfn3x3-8 1 2 3 4 8 7 6 5 thermal pad G784/G784-1 note: recommend connecting the thermal pad to the gnd or let it keep floating. therm dxn vcc dxp smbdata smbclk gnd alert
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