PDF G771 Data sheet ( Hoja de datos )

Número de pieza	G771
Descripción	Two Remote Temperature Sensors with SMBus Serial Interface and System Reset Circuit
Fabricantes	ETC
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No Preview Available ! Global Mixed-mode Technology Inc. G771 Two Remote Temperature Sensors with SMBus Serial Interface and System Reset Circuit Features Measures Two Remote Temperatures No Calibration Required SMBus 2-Wire Serial Interface Programmable Under/Over-temperature Alarms Programmable Thermal Shutdown Signal Supports SMBus Alert Response Accuracy: ±5°C (-40°C to + 125°C, remote) ±3°C (+60°C to + 100°C, remote) 4.5V to 5.5V Supply Range Precision Monitoring of 5V Power-Supply Voltage 140ms Min Power-On Reset Pulse Width RESET Output Guaranteed RESET Valid to VCC=1V Power Supply Transient Immunity No External Components needed for reset function Small, 16-Pin SSOP Package Applications Desktop and Notebook Central Office Computers Telecom Equipment Smart Battery Packs Test and Measurement LAN Servers Multi-Chip Modules Industrial Controls General Description The G771 contains a precise digital thermometer, a system-reset circuit, and a programmable thermal shutdown signal. The thermometer reports the temperature of 2 remote sensors. The remote sensors are diode-connected transistors typically a low-cost, easily mounted 2N3904 NPN type that replace conventional thermis- tors or thermocouples. Remote accuracy is ±5°C for multiple transistor manufacturers, with no calibration needed. 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 (SMBusTM) Write Byte, Read Byte, Send Byte, and Receive Byte commands to program the alarm thresholds and to read temperature data. The data format is 7 bits plus sign, with each bit cor- responding to 1°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. Ordering Information PART* G771 TEMP. RANGE -55°C to +125°C PIN-PACKAGE 16SSOP Pin Configuration NC 1 Vcc 2 DXP1 3 DXN 4 DXP2 5 NC 6 DGND 7 AGND 8 G771 16 TH_SHUT(push-pull) 15 NC 14 SMBCLK 13 NC 12 SMBDATA 11 ALERT 10 NC 9 RESET 16Pin SSOP Ver 0.2 Preliminary Dec 11, 2001 TEL: 886-3-5788833 http://www.gmt.com.tw 1 1 page Global Mixed-mode Technology Inc. G771 Detailed Description The G771 (patents pending) consists of two tempera- ture sensors, one on-chip temperature sensor and provides system-reset function. The temperature sensor is designed to work in con- junction with an external micro-controller (µC) or other intelligence in thermostatic, process-control, or moni- toring applications. The µC is typically a powerman- agement or keyboard controller, generating SMBus se- rial commands by "bit-banging" general-purpose in- put-output (GPIO) pins or via a dedicated SMBus inter- face block. Essentially a 12-bit serial analog-to-digital converter (ADC) with a sophisticated front end, the G771 con- tains a switched current source, a multiplexer, an ADC, an SMBus interface, a reset circuit and associated control logic (Figure 1). Temperature data from the ADC is loaded into two data registers, where it is automatically compared with data previously stored in four over/under-temperature alarm registers. ADC and Multiplexer The ADC is an averaging type that integrates over a 60ms period (each channel, typical). The multiplexer automatically steers bias currents through two remote diodes, measures their forward voltages, and computes their temperatures. All chan- nels are converted automatically once the conversion process has started, either in free-running or sin- gle-shot mode. If one of the two channels is not used, the device still performs all measurements, and the user can simply ignore the results of the unused chan- nel. If the remote diode channel is unused, tie DXPx to DXN rather than leaving the pins open. The DXN input is internally connected to the ground node inside the chip 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 causes about +1/2°C error per ohm. Likewise, 200µV of offset voltage forced on DXP-DXN causes about 1°C error. VCC VCC DXP1 DXP2 DXN INTERNAL GROUND CONTROL LOGIC THERMAL SHUTDOWN LOGIC TH_SHUT SMBUS REGISTERS SMBCLK SMBDATA ALERT + + MUX + ADC RESET CIRCUIT RESET Fig 1. Functional Diagram Ver 0.2 Preliminary Dec 11, 2001 TEL: 886-3-5788833 http://www.gmt.com.tw 5 5 Page Global Mixed-mode Technology Inc. G771 Configuration Byte Functions The configuration byte register contents are listed in table 5. Bit 7 (MASK) is used to mask ALERT inter- rupt. Bit 6 ( RUN /STOP) is to put the device in software standby mode. Setting bit 5 (DET_FAN) with logic 1 can activate the detection of fan failure. Logic 1 in bit 4 (EN_TH_SHUT) makes thermal shutdown function valid and logic 0 disables this function and keep TH_SHUT pin low. Bit 3~0 forms thermal shutdown fault queue. The number of faults these bits decided are listed in table 6. Thermal Status Byte Functions The thermal status byte register (02h) (Table 6) indi- cates which (if any) temperature thresholds have been exceeded. This byte also indicates whether or not the ADC is converting and whether there is an open circuit in the remote diode DXPx-DXN path. After POR, the normal state of all the flag bits is zero, assuming none of the alarm conditions are present. The status byte is cleared by any successful read of the status, unless the fault persists. Note that the ALERT interrupt latch is not automatically cleared when the status flag bit is cleared. When reading the status byte, you must check for in- ternal bus collisions caused by asynchronous ADC timing, or else disable the ADC prior to reading the status byte (via the RUN /STOP bit in the configura- tion byte). In one-shot mode, read the status byte only after the conversion is complete, which is 150ms max after the one-shot conversion is commanded. Table 5. Configuration-Byte Bit Assignments BIT 7 (MSB) 6 5 4 3-0 NAME MASK RUN / STOP DET_FAN EN_TH_SHUT FQ_TH_SHUT POR STATE FUNCTION 0 Masks all ALERT interrupts when high. Standby mode control bit. If high, the device immediately stops converting and en- 0 ters standby mode. If low, the device converts in either one-shot or timer mode. 0 Should be 0. Changing this to 1 will cause ALERT function abnormal. 1 Validation of the fault queue function of thermal shutdown. 0010b Fault Queue. Number of faults necessary to detect before setting TH_SHUT output to avoid false tripping due to noise. Table 6. Number of Faults assigned by FQ_TH_SHUT FQ_TH_SHUT 0000b 0001b 0010b 0011b 0100b 0101b 0110b 0111b Number of Faults 1 2 3(Power-up default) 4 5 6 7 8 FQ_TH_SHUT 1000b 1001b 1010b 1011b 1100b 1101b 1110b 1111b Number of Faults 9 10 11 12 13 14 15 16 Ver: 0.2 Preliminary Dec 11, 2001 TEL: 886-3-5788833 http://www.gmt.com.tw 11 11 Page

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