SS8017 Two Remote Temperature Sensors with SMBus Serial Interface and System Reset Features Description Two channels: measures both remote and local temperatures No calibration required SMBus 2-wire serial interface Programmable under/over-temperature alarms SMBus alert response supported Accuracy: ±1°C (+60°C to +100°C, remote) ±3°C (+60°C to + 100°C, local) Average supply current during conversion of 320µA (typ) Supply range of +3V to +5.5V Small 8-lead SO package Applications Desktop and Notebook Computers Smart Battery Packs LAN Servers Industrial Controllers Central Office Telecom Equipment Test and Measurement Multi-Chip Modules The SS8017 contains a precise digital thermometer, a system-reset circuit, and a programmable thermal shutdown signal. The thermometer reports the temperature of two remote sensors. The remote sensors are diode-connected transistors , typically a low-cost, eas ily mounted 2N3904 NPN type which replaces conve ntional thermistors 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 (SMBus TM) 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 corresponding to 1°C, in two’s-complement format. Measurements can be done automatically and autonomously, with the conve rsion rate programmed by the user or programmed to operate in a single-shot mode. The adjustable rate a llows the user to control the supply-current drain. Ordering Information SS8017XX Packing type TR: Tape and reel Example: SS8017TR à SS8017 shipped in tape and reel Rev.2.01 6/06/2003 www.SiliconStandard.com 1 of 16 SS8017 The SS8017 also contains a microprocessor (µP)supervisory circuit used to monitor the power supplies in µP and digital systems. This provides excellent circuit reliability and low cost by eliminating external components and adjustments when used with 5V-powered circuits. This circuit asserts a reset signal whenever the VCC supply voltage declines below a preset threshold, keeping it asserted for at least 140ms after VCC has risen above the reset threshold. The SS8017 has an active-low RESET output. The reset comparator is designed to ignore fast transients on VCC. Reset threshold of this circuit is set to 4.38V. number of times equal to the number of faults of the FQ_TH_SHUT registers, TH_SHUT pin becomes logic high. The same mechanism is duplicated for DX2. Therefore, if either DX1 or DX2 continuously exceeds their respective Tcrit, the TH_SHUT will a ssert logic high to indicate a thermal shutdown event. The SS8017’s SMBus device address is fixed to be 7Ah for write and 7Bh for read. The SS8017 is available in a small, 16-pin SSOP surface-mount package. When the temperature of DX1 reaches or exceeds the Tcrit1 (SMBus 35h) threshold consecutively for the Typical Operating Circuit TH_SHUT Vcc Vcc 0.1µF 0.1µF 10k EACH SS8017 DXP1 DXN 2N3904 SMBCLK SMBDATA SMBCLK SMBDATA 2200pF ALERT INTERRUPT TO µC DXP2 2N3904 RESET 2200pF RESET µP GND Rev.2.01 6/06/2003 www.SiliconStandard.com 2 of 16 SS8017 Absolute Maximum Ratings VCC to GND………….….………………………………………………..……….-0.3V to +6V DXP to GND……….……………………………………………………..……..…-0.3V to VCC + 0.3V DXN to GND………………………………………………….……..……………..-0.3V to +0.8V SMBCLK, SMBDATA, ALERT to GND……………………………………...…-0.3V to +6V SMBDATA, ALERT Current………………………………………………..…….-1mA to +50mA DXN Current………………………………………………..…..………………….±1mA ESD Protection (SMBCLK, SMBDATA, ALERT , human body model).…….2000V ESD Protection (other pins, human body model)……………………………….2000V Continuous Power Dissipation (T A = +70°C) …………………………….SOP (derate 8.30mW/°C above +70°C)………………………………………….......667mW Operating Temperature Range…………………………………………………-20°C to +120°C Junction Temperature………………………………………………….………..+150°C Storage temperature Range…………………………………………………….-65°C to +165°C Lead Temperature (soldering, 10sec)……………………………………..……...+300°C Electrical Characteristics (VCC = + 3.3V, TA = 0°C to +85°C, unless otherwise noted.) PARAMETER Temperature Error, Remote Diode (Note 1) Temperature Error, Local Diode CONDITIONS -1 +1 TR = 0°C to +125°C (Note 2) -3 +3 TA = +60°C to +100°C -3 +3 TA = 0°C to +85°C (Note 2) -5 +5 Supply-Voltage Range 3.0 Undervoltage Lockout Threshold VCC input, disables A/D conversion, rising edge Undervoltage Lockout Hysteresis Power-On Reset Threshold VCC, falling edge POR Threshold Hysteresis Conversion Time From stop bit to conversion complete (both channels) Remote-Diode Source Current Rev.2.01 6/06/2003 50 mV V 50 mV 4 Auto-convert mode. Logic inputs forced to VCC or GND 0.5 conv/sec 35 8.0 conv/sec 320 Conversion-Rate Control Byte=04h, 1Hz µA µA 125 ms 1 sec High level 176 Low level 11 www.SiliconStandard.com V 1.7 3 Average Operating Supply Current °C V Hardware or software standby, SMBCLK at 10kHz Logic inputs forced to VCC or GND DXP forced to 1.5V 5.5 °C 2.8 SMBus static Standby Supply Current Conversion Rate Timing MIN TYP MAX UNITS TR = +60°C to +100°C, VCC = 3.0V to 3.6V µA 3 of 16 SS8017 Electrical Characteristics (cont.) (VCC = + 3.3V, TA = 0°C to +85°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS SMBus Interface Logic Input High Voltage SMBCLK, SMBDATA; Vcc = 4.5V to 5.5V Logic Input Low Voltage SMBCLK, SMBDATA; Vcc = 4.5V to 5.5V 2.4 Logic Output Low Sink Current , SMBDATA forced to 0.4V Output High Leakage Current forced to 5.5V Logic Input Current Logic inputs forced to Vcc or GND SMBus Input Capacitance SMBCLK, SMBDATA SMBus Clock Frequency (Note 4) DC SMBCLK Clock Low Time tLOW , 10% to 10% points 4.7 µs SMBCLK Clock High Time tHIGH , 90% to 90% points 4 µs 6 1 µA 2 µA 100 KHz 5 tSU : STA , 90% to 90% points V mA -2 SMBus Start-Condition Setup Time SMBus Repeated Start-Condition Setup Time V 0.8 pF 4.7 µs 500 ns SMBus Start-Condition Hold Time tHD: STA , 10% of SMBDATA to 90% of SMBCLK 4 µs SMBus Start-Condition Setup Time tSD: STO , 90% of SMBDATA to 10% of SMBDATA 4 µs SMBus Data Valid to SMBCLK Rising-Edge Time tSU: DAT , 10% or 90% of SMBDATA to 10% of SMBCLK 800 ns SMBus Data-Hold Time tHD : DAT(Note 5) 0 µs SMBCLK Falling Edge to SMBus Data-Valid Master clocking in data Time (V CC =full range, TA= 60°C, unless otherwise noted.) PARAMETER SYMBOL Reset Threshold 1 CONDITIONS VTH MIN 4.2 Reset Active Timeout Period TYP 4.4 MAX UNITS 4.5 340 Output Voltage Low V OL V CC=V T H min ISINK =3.2mA RESET Output Voltage High V OH V CC>V T H max, ISOURCE =5.0mA V ms 0.4 V CC-1.5 µs V V Note 1: Guaranteed but not 100% tested. Note 2: Quantization error is not included in specifications for temperature accuracy. For example if the SS8017 device temperature is exactly +66.7°C, or +68°C (due to the quantization error plus the +1/2°C offset used for rounding up) and still be within the guaranteed ±3°C error limits for the +60°C to +100°C temperature range. See Table3. Note 3: A remote diode is any diode-connected transistor from Table1. TR is the junction temperature of the remote diode. See Remote Diode Selection for remote diode forward voltage requirements. Note 4: The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it violates the 10k Hz minimum clock frequency and SMBus specifications, and may monopolize the bus. Note 5: Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of SMBCLK's falling edge. Rev.2.01 6/06/2003 www.SiliconStandard.com 4 of 16 SS8017 Pin Description PIN NAME FUNCTION 1,6,10,13,15 NC Not connected. 2 Vcc Supply Voltage Input, 4.5V to 5.5V. Bypass to GND with a 0.1µF capacitor. 3 DXP1 Combined Current Source and A/D Positive Input for remote-diode channel 1. Do not leave DXP1 floating; tie DXP1 to DXN if no remote diode on channel 1 is used. Place a 2200pF capacitor between DXP1 and DXN for noise filtering. 4 DXN Combined Current Sink and A/D Negative Input. DXN is common negative node of both remote diodes on channel 1 and 2. The traces of DXP1-DXN and DXP2-DXN pairs should be routed independently. The common DXN should be connected together as close as possible to the IC. DXN is internally connected to the GND pin for signal ground use. 5 DXP2 Combined Current Source and A/D Positive Input for remote-diode channel 2. Do not leave DXP2 floating; tie DXP2 to DXN if no remote diode on channel 2 is used. Place a 2200pF capacitor between DXP2 and DXN for noise filtering. 7 DGND Digital Ground. 8 AGND Analog Ground. 9 RESET 11 12 ALERT RESET Output remains low while VCC is below the reset threshold, and for 240ms after VCC rises above the reset threshold. SMBus Alert (interrupt) Output, open drain. SMBDATA SMBus Serial-Data Input / Output, open drain. 14 SMBCLK SMBus Serial-Clock Input. 16 TH_SHUT Thermal Shutdown Output, push-pull output. Pin Configuration NC 1 16 TH_SHUT(push-pull) Vcc 2 15 NC DXP1 3 14 SMBCLK DXN 4 13 NC DXP2 5 12 SMBDATA NC 6 11 ALERT DGND 7 10 NC AGND 8 9 RESET SSOP-16L Rev.2.01 6/06/2003 www.SiliconStandard.com 5 of 16 SS8017 Block Diagram THERMAL SHUTDOWN LOGIC V CC VCC TH_SHUT SMBCLK SMBUS REGISTERS CONTROL LOGIC SMBDATA ALERT DXP1 + DXP2 + MUX + ADC DXN RESET CIRCUIT RESET INTERNAL GROUND Detailed Description The SS8017 consists of two temperature sensors, one on-chip temperature sensor and includes a system-reset function. The temperature sensor is designed to work in conjunction with an external micro-controller (µC) or other intelligence in thermostatic, process-control, or monitoring applications. The µC is typically a powermanagement or keyboard controller, generating SMBus serial commands by "bit-banging" general-purpose input -output (GPIO) pins or via a dedicated SMBus interface block. Essentially a 12-bit serial analog-to-digital converter (ADC) with a sophisticated front end, the SS8017 contains a switched current source, a multiplexer, an ADC, an SMBus interface, a reset circuit and associated control logic (see block diagram above). 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. Rev.2.01 6/06/2003 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 channels are converted automatically 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 all measurements, and the user can simply ignore the results of the unused channel. 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. www.SiliconStandard.com 6 of 16 SS8017 A/D Conversion Sequence If a Start command is written (or generated automatically in the free-running auto-convert mode), both two channels are converted, and the results of both measurements are available after the end of conversion. A BUSY status bit in the status byte shows that the device is actually performing a new conversion; however, even if the ADC is busy, the results of the previous conversion are always available. Remote-Diode Selection Temperature accuracy depends on having a good-quality, diode-connected small-signal transistor. Accuracy has been experimentally verified for all of the devices listed in Table 1. The 8017 can also directly measure the die temperature of CPUs and other integrated circuits having on-board temperature- sensing diodes. The transistor must be a small-signal type with a relatively high forward voltage; otherwise, the A/D input voltage range can be violated. The forward voltage must be greater than 0.25V at 10µA; check to ensure this is true at the highest expected temperature. The forward voltage must be less than 0.95V at 200A; check to ensure this is true at the lowest expected temperature. Large power transistors don't work at all. Also, ensure that the base resistance is less than 100Ω. Tight specifications for forward current gain (+50 to +150, for example) indicate that the manufacturer has good process controls and that the devices have consistent VBE characteristics. Thermal Mass and Self-Heating Thermal mass can seriously degrade the 8017's effective accuracy. The thermal time constant of the SSOP-16 package is about 140sec in still air. For the 8017 junction temperature to settle to within +1°C after a sudden +100°C change requires about five time constants or 12 minutes. The use of smaller packages for remote sensors, such as SOT23s, improves the situation. Take care to account for thermal gradients between the heat source and the sensor ,and ensure that stray air current across the sensor package does not interfere with measurement accuracy. Table 1. Remote-Sensor Transistor Manufacturers MANUFACTURER MODEL NUMBER Philips PMBS 3904 Motorola (USA) MMBT3904 National Semiconductor (USA) MMBT3904 Note:Transistors must be diode-connected (base short -ed to collector). ADC Noise Filtering The ADC is an integrating type with inherently good noise rejection, especially of low-frequency signals Rev.2.01 6/06/2003 such as 60Hz/120Hz power-supply hum. Micro-power operation places constraints on high-frequency noise rejection; therefore, careful PC board layout and proper external noise filtering are required for high- accuracy remote measurements in electrically noisy environments. High-frequency EMI is best filtered at DXP and DXN with an external 2200pF capacitor. This value can be increased to about 3300pF(max), including cable capacitance. Higher capacitance than 3300pF introduces errors due to the rise time of the switched current source. Nearly all noise sources tested cause the ADC measurements to be higher than the actual temperature, typically by +1°C to 10°C, depending on the frequency and amplitude (see Typical Operating Characteristics). PC Board Layout Place the 8017 as close as practical to the remote diode. In a noisy environment, such as a computer motherboard, this distance can be 4 in. to 8 in. (typical) or more as long as the worst noise sources (such as CRTs, clock generators, memory buses, and ISA/PCI buses) are avoided. Do not route the DXP -DXN lines next to the deflection coils of a CRT. Also, do not route the traces across a fast memory bus, which can easily introduce +30°C error, even with good filtering, Otherwise, most noise sources are fairly benign. Route the DXP and DXN traces in parallel and in close proximity to each other, away from any high-voltage traces such as +12VDC. Leakage currents from PC board contamination must be dealt with carefully, since a 20MΩ leakage path from DXP to ground causes about +1°C error. Route the 2 pairs of DXP1-DXN and DXP2-DXN traces independently (Figure 2a). Connect the common DXN as close as possible to the DXN pin on IC (Figure 2a). Connect guard traces to GND on either side of the DXP-DXN traces (Figure 2b). With guard traces in place, routing near high-voltage traces is no longer an issue. Route through as few vias and crossunders as possible to minimize copper/solder thermocouple effects. When introducing a thermocouple, make sure that both the DXP and the DXN paths have matching thermocouples. In general, PC board- induced thermocouples are not a serious problem, A copper-solder thermocouple exhibits 3µV/°C, and it takes about 200µV of voltage error at DXP -DXN to cause a +1°C measurement error. www.SiliconStandard.com 7 of 16 SS8017 In this way, most parasitic thermocouple errors are swamped out. Use wide traces. Narrow ones are more inductive and tend to pick up radiated noise. The 10 mil widths and spacing recommended on Figure 2 aren't absolutely necessary (as they offer only a minor improvement in leakage and noise), but try to use them where practical. Keep in mind that copper can't be used as an EMI shield, and only ferrous materials such as steelwork will. Placing a copper ground plane between the DXP DXN traces and traces carrying high-frequency noise signals do not help reduce EMI. PC Board Layout Checklist n Place the 8017 close to a remote diode. n Keep traces away from high voltages (+12V bus). n Keep traces away from fast data buses and CRTs. n Use recommended trace widths and spacing. n Place a ground plane under the traces n Use guard traces flanking DXP and DXN and connecting to GND. n Route two DXPx-DXN pairs independently n Connect the common DXN as close as possible to the DXN pin on IC. n Place the noise filter and the 0.1µF Vcc bypass capacitors close to the 8017. GND DXP1 DXN DXP1 DXN SS8017 DXN DXP2 DXP2 GND Chip Boundary Fig 2(a) Connect the common DXN as close as possible to the DXN pin on IC. GND 10 MILS 10 MILS DXP MINIMUM 10 MILS DXN 10 MILS GND Twisted Pair and Shielded Cables For remote-sensor distances longer than 8 in., or in particularly noisy environments, a twisted pair is recommended. Its practical length is 6 feet to 12 feet (typical) before noise becomes a problem, as tested in a noisy electronics laboratory. For longer distances, the best solution is a shielded twisted pair like that used for audio microphones. Connect the twisted pair to DXP and DXN and the shield to GND, and leave the shield's remote end unterminated. Excess capacitance at DX_ limits practical remote sensor distances (see Typical Operating Characteristics), For very long cable runs, the cable's parasitic capacitance often provides noise filtering, so the 2200pF capacitor can often be removed or reduced in value. Cable resistance also affects remote-sensor accuracy; 1Ω series resistance introduces about + 1°C error. Low-Power Standby Mode Standby mode disables the ADC and reduces the supply-current drain to less than 10µA. Enter standby mode via the RUN/STOP bit in the configuration byte register. In standby mode, all data is retained in memory, and the SMB interface is alive and listening for reads and writes. This is valid for temperature sensor only. Standby mode is not a shutdown mode. With activity on the SMBus, extra supply current is drawn (see Typical Operating Characteristics). In software standby mode, the 8017 can be forced to perform temperature measurement via the one-shot command, despite the RUN/STOP bit being high. Supply-current drain during the 125ms conversion period is always about 500µA. Slowing down the conversion rate reduces the average supply current (see Typical Operating Characteristics). In between conversions, the instantaneous supply current is about 200µA due to the current consumed by the system resetting circuit. Reset Immunity Negative-Going VCC Transients In addition to issuing a reset to the microprocessor (µP) during power-up, power-down, and brownout conditions, the 8017 is relatively immune to short duration negative-going VCC transients (glitches). Typically, for the 8017, a V CC transient that goes 100mV below the reset threshold and lasts 20µs or less will not cause a reset pulse. A 0.1µF bypass capacitor mounted as close as possible to the VCC pin provides additional transient immunity. Fig 2 (b) Recommended DXP/DXN PC Rev.2.01 6/06/2003 www.SiliconStandard.com 8 of 16 SS8017 Ensuring a Valid Reset Output Down to VCC = 0V When VCC falls below 1V, the SS8017 RESET output no longer sinks current-it becomes an open circuit. Therefore, high-impedance CMOS logic inputs connected to RESET can drift to undetermined voltages. This presents no problem in most applications, since most µP and other circuitry is inoperative with VCC below 1V. However, in applications where RESET must be valid down to 0V, adding a pull-down resistor to RESET causes any stray leakage currents to flow to ground, holding RESET low (Figure 3). R1's value is not critical; 100kΩ is large enough not to load RESET and small enough to pull RESET to ground. Interfacing to µPs with Bi-directional Reset Pins A µP with bi-directional reset pins (such as the Motorola 68HC11 series) can connect to the SS8017 reset output. If, for example, the SS8017 RESET output is asserted high and the µP wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7kΩ resistor between the SS8017 RESET output and the µP reset I/O (Figure 4). Buffer the SS8017 RESET output to other system components. Benefits of Highly Accurate Reset Threshold Most µP supervisor Ics have reset threshold voltages between 5% and 10% below the value of nominal supply voltages. This ensures a reset will not occur within 5% of the nominal supply, but will occur when the supply is 10% below nominal. When using ICs rated at only the nominal supply ±5% this leaves a zone of uncertainty where the supply is between 5% and 10% low, and where the reset may or may not be asserted. The SS8017 uses highly accurate circuitry to ensure that reset is asserted close to the 5% limit, and long before the supply has declined to 10% below nominal. SMBus Digital Interface From a software perspective, the SS8017 appears as a set of byte-wide registers that contain temperature data, alarm threshold values, fan speed data, or control bits, A standard SMBus 2-wire serial interface is used to read temperature data and write control bits and alarm threshold data. Each A/D and fan control channel within the device responds to the same SMBus slave address for normal reads and writes. The SS8017 employs four standard SMBus protocols: Write Byte, Read Byte, Send Byte, and Receive Byte (Figure 5). The shorter Receive Byte protocol allows quicker transfers, provided that the correct data register was previously selected by a Read Byte instruction. Use caution with the shorter protocols in multi-master systems, since a second master could over-write the command byte without informing the first master. The temperature data format is 7bits plus sign in twos-complement form for each channel, with each data bit representing 1°C (Table3), transmitted MSB first. Measurements are offset by +1/2°C to minimize internal rounding errors; for example, +99.6°C is reported as +100°C. Fig 4. Interfacing to µPs with Bi-directional Reset I/O Fig 3. RESET Valid to VCC = Ground Circuit BUFFER VCC V CC SS8017 RESET SS8017 BUFFERED RESET TO OTHER SYSTEM COMPONENTS VCC 4.7k µP RESET RESET R1 100k GND GND GND Rev.2.01 6/06/2003 www.SiliconStandard.com 9 of 16 SS8017 Write Byte Format S Address WR ACK Command 7 bits ACK DATA 8 bits ACK P 8 bits 1 Slave Address: equivalent to chip-select line of a 3-wire interface Command Byte: selects, which register you, are writing to Data Byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sampling rate) Read Byte Format S Address WR ACK 7 bits Command ACK S Address 8 bits RD ACK DATA 7 bits /// P 8 bits Slave Address: equivalent to chip- select line Command Byte: selects, which register you, are reading from Slave Address: repeated due to change in data-flow direction Data byte: reads from the register set by the command byte Send Byte Format S Address WR ACK 7 bits Command ACK P 8 bits Command Byte: sends command with no data usually used for one-shot command Receive Byte Format S Address 7 bits RD ACK Data /// P 8 bits Data Byte: reads data from the register commanded by the last Read Byte or Write Byte transmission; also used for SMBus Alert Response return address S = Start condition Shaded = Slave transmission P = Stop condition /// = Not acknowledged Fig 5. SMBus Protocols Rev.2.01 6/06/2003 www.SiliconStandard.com 10 of 16 SS8017 Table 3. Data Format (Twos-Complement) ROUND DIGITAL OUTPUT TEMP. TEMP. DATA BITS (°C) (°C) SIGN MSB LSB +130.00 +127 0 111 1111 +127.00 +127 0 111 1111 +126.50 +127 0 111 1111 +126.00 +126 0 111 1110 +25.25 +25 0 001 1001 +0.50 +1 0 000 0001 +0.25 +0 0 000 0000 +0.00 +0 0 000 0000 -0.25 +0 0 000 0000 -0.50 +0 0 000 0000 -0.75 -1 1 111 1111 -1.00 -1 1 111 1111 -25.00 -25 1 110 0111 -25.50 -25 1 110 0110 -54.75 -55 1 100 1001 -55.00 -55 1 100 1001 -65.00 -65 1 011 1111 -70.00 -65 1 011 1111 Alarm Threshold Registers Four registers store alarm threshold data, with high-temperature (THIGH) and low-temperature (TLOW) registers for each A/D channel. If either measured temperature equals or exceeds the corresponding alarm threshold value, an ALERT interrupt is asserted. The power-on-reset (POR) state of both THIGH registers is full scale (0111 1111, or +127°C). The POR state of both TLOW registers is 1100 1001 or -55°C. Diode Fault Alarm There is a continuity fault detector at DXP that detects whether the remote diode has an open-circuit condition. At the beginning of each conversion, the diode fault is checked, and the status byte is updated. This fault detector is a simple voltage detector; if DXP rises above VCC - 1V (typical) due to the diode current source, a fault is detected. Note that the diode fault isn't checked until a conversion is initiated, so immediately after Rev.2.01 6/06/2003 power-on reset the status byte indicates no fault is present, even if the diode path is broken. If the remote channel is shorted (DXP to DXN or DXP to GND), the ADC reads 0000 0000 so as not to trip either the THIGH or TLOW alarms at their POR settings. In applications that are never subjected to 0°C in normal operation, a 0000 0000 result can be checked to indicate a fault condition in which DXP is accidentally short circuited. Similarly, if DXP is short circuited to VCC, the ADC reads +127°C for both channels, and the device alarms. ALERT Interrupts The ALERT interrupt output signal is latched and can only be cleared by reading the Alert Response address. Interrupts are generated in response to THIGH and TLOW comparisons and when the remote diode is disconnected (for continuity fault detection). The interrupt does not halt automatic conversions; new temperature data continues to be available over the SMBus interface after ALERT is asserted. The interrupt output pin is open-drain so that device can share a common interrupt line. The interrupt rate can never exceed the conversion rate. The interface responds to the SMBus Alert Response address, an interrupt pointer return-address feature (see Alert Response Address section). Prior to taking corrective action, always check to ensure that an interrupt is valid by reading the current temperature. Alert Response Address The SMBus Alert Response interrupt pointer provides quick fault identification for simple slave devices that lack the complex, expensive logic needed to be a bus master. Upon receiving an ALERT interrupt signal, the host master can broadcast a Receive Byte transmission to the Alert Response slave address (0001 100). Then any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus. www.SiliconStandard.com 11 of 16 SS8017 Table 4. Command-Byte Bit Assignments REGISTER COMMAND POR STATE FUNCTION RRTE2 00h 0000 0000b Read 2nd remote temperature: returns latest temperature RRTE1 01h 0000 0000b Read 1st remote temperature: returns latest temperature RSL 02h N/A RCL 03h 0000 0000b Read configuration byte RCRA 04h 0000 0010b Read conversion rate byte RRHI2 05h RRLS2 06h 1100 1001b(-55) RRHI1 07h 0111 1111b (127) Read 1st remote THIGH limit RRLS1 08h 1100 1001b (-55) Read 1st remote TLOW limit WCA 09h N/A Write configuration byte WCRW 0Ah N/A Write conversion rate byte WRHA2 0Bh N/A Write 2nd remote THIGH limit WRLN2 0Ch N/A Write 2nd remote TLOW limit WRHA1 0Dh N/A Write 1st remote THIGH limit WRLN1 0Eh N/A Write 1st remote TLOW limit OSHT 0Fh N/A One-shot command (use send-byte format) TCRIT1 35h 0110 1100b (108) Critical temperature for 1st remote temperaure sensor TCRIT2 36h 0101 1000b (88) Read status byte (flags, busy signal) 0111 1111b (127) Read 2nd remote THIGH limit Read 2nd remote TLOW limit Critical temperature for 2nd remote temperaure sensor The Alert Response can activate several different slave devices simultaneously, similar to the SMBus General Call. If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address code wins. The losing device does not generate an acknowledge and continues to hold the ALERT line low until serviced (implies that the host interrupt input is level sensitive). Successful reading of the alert response address clears the interrupt latch. Command Byte Functions The 8-bit command byte register (Table 4) is the master index that points to the various other registers within the SS8017. The register's POR state is 0000 0000, so that a Receive Byte transmission (a protocol that lacks the command byte) that occurs immediately after POR returns the current local temperature data. The one-shot command immediately forces a new conversion cycle to begin. In software standby mode ( RUN /STOP bit = high), a new conversion is begun, after which the device returns to standby mode. If a conversion is in progress when a one-shot command is received in auto-convert mode (RUN/STOP bit = low) between conversions, a new conversion begins, the conversion rate timer is reset, and the next automatic conversion takes place after a full delay elapses. Configuration Byte Functions The configuration byte register contents are listed in Rev.2.01 6/06/2003 table 5. Bit 7 (MASK) is used to mask ALERT interrupt. 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) indicates 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 internal 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 configuration 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. www.SiliconStandard.com 12 of 16 SS8017 Table 5. Configuration-Byte Bit Assignments BIT NAME POR STATE 7 (MSB) MASK 0 FUNCTION Masks all ALERT interrupts when high. 6 RUN / STOP 0 Standby mode control bit. If high, the device immediately stops converting and enters standby mode. If low, the device converts in either one-shot or timer mode. 5 DET_FAN 0 Should be 0. Changing this to 1 will cause ALERT function abnormal. 4 EN_TH_SHUT 1 Validation of the fault queue function of thermal shutdown. 3-0 FQ_TH_SHUT 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 Number of Faults FQ_TH_SHUT 0000b 1 1000b Number of Faults 9 0001b 2 1001b 10 0010b 3(Power-up default) 1010b 11 0011b 4 1011b 12 0100b 5 1100b 13 0101b 6 1101b 14 0110b 7 1110b 15 0111b 8 1111b 16 Table 7. Status-Byte Bit Assignments BIT NAME 7(MSB) BUSY FUNCTION 6 RHIGH2* A high indicates that the 2nd diode high-temperature alarm has activated. 5 RLOW2* A high indicates that the 2nd diode low -temperature alarm has activated. 4 RHIGH1* A high indicates that the 1st diode high-temperature alarm has activated. 3 RLOW1* A high indicates that the 1st diode low -temperature alarm has activated. 2 OPEN* 1 RFU Reserved for future use (returns 0) 0(LSB) RFU Reserved for future use (returns 0) A high indicates that the ADC is busy converting. A high indicates a remote-diode continuity (open-circuit) fault. *These flags stay high until cleared by POR, or until the status byte register is read. Table 8. Conversion-Rate Control Byte DATA CONVERSION RATE (Hz) Temperature Sensor Average Supply Current (µA TYP, at Vcc = 5V) 00h 0.0625 30 01h 0.125 33 02h 0.25 35 03h 0.5 48 04h 1 70 05h 2 128 06h 4 225 07h 8 425 08h to FFh RFU - Rev.2.01 6/06/2003 www.SiliconStandard.com 13 of 16 SS8017 Table 9. RLTS and RRTE Temp Register Update Timing Chart OPERATING MODE CONVERSION INITIATED BY: NEW CONVERSION RATE (CHANGED VIA WRITE TO CRW) TIME UNTIL RLTS AND RRTE ARE UPDATED Auto-Convert Power-on reset N/A (0.25Hz) 156ms max Auto-Convert 1-shot command, while idling between automatic conversions N/A 156ms max Auto-Convert 1-shot command that occurs during a conversion N/A When current conversion is complete (1-shot is ignored) Auto-Convert Rate timer 0.0625Hz 20sec Auto-Convert Rate timer 0.125Hz 10sec Auto-Convert Rate timer 0.25Hz 5sec Auto-Convert Rate timer 0.5Hz 2.5sec Auto-Convert Rate timer 1Hz 1.25sec Auto-Convert Rate timer 2Hz 625ms Auto-Convert Rate timer 4Hz 312.5ms Auto-Convert Rate timer 8Hz 237.5ms Software Standby RUN/STOP bit N/A 156ms Software Standby 1-shot command N/A 156ms To check for internal bus collisions, read the status byte. If the least significant seven bits are ones, discard the data and read the status byte again. The status bits LHIGH, LLOW, RHIGH, and RLOW are refreshed on the SMBus clock edge immediately following the stop condition, so there is no danger of losing temperature-related status data as a result of an internal bus collision. The OPEN status bit (diode continuity fault) is only refreshed at the beginning of a conversion, so OPEN data is lost. The ALERT interrupt latch is independent of the status byte register, so no false alerts are generated by an internal bus collision. When auto-converting, if the THIGH and TLOW limits are close together, it's possible for both high-temp and low-temp status bits to be set, depending on the amount of time between status read operations (especially when converting at the fastest rate). In these circumstances, it's best not to rely on the status bits to indicate reversals in long-term temperature changes and instead use a current temperature reading to establish the trend direction. Temperature Conversion Rate Byte The conversion rate register (Table 7) programs the time interval between conversions in free running auto-convert mode. This variable rate control reduces the supply current in portable-equipment applications. The conversion rate byte's POR state is 02h (0.25Hz). Rev.2.01 6/06/2003 The SS8017 looks only at the 3 LSB bits of this register, so the upper 5 bits are "don't care" bits, which should be set to zero. The conversion rate tolerance is ±25% at any rate setting. Valid A/D conversion results for all channels are available one total conversion time (125ms nominal, 156ms maximum) after initiating a conversion, whether conversion is initiated via the RUN/STOP bit, one-shot command, or initial power-up. Changing the conversion rate can also affect the delay until new results are available. See Table 8. Slave Addresses The SS8017 appears to the SMBus as one device having a common address for all the ADC and fan control channels. The device address is fixed to be 7Ah for write and 7Bh for read. The SS8017 also responds to the SMBus Alert Response slave address (see the Alert Response Address section). POR and UVLO The SS8017 has a volatile memory. To prevent ambiguous power-supply conditions from corrupting the data in memory and causing erratic behavior, a POR voltage detector monitors Vcc and clears the memory if Vcc falls below 1.7V (typical, see Electrical Characteristics table). When power is first applied and Vcc rises above 1.75V (typical), the logic blocks begin operating, although reads and writes at VCC levels www.SiliconStandard.com 14 of 16 SS8017 though reads and writes at VCC levels below 3V are not recommended. A second Vcc comparator, the ADC UVLO comparator, prevents the ADC from converting until there is sufficient headroom (Vcc = 2.8V typical). Power-Up Defaults: n Interrupt latch is cleared. n ADC begins auto /converting at a 0.25Hz rate. n Command byte is set to 00h to facilitate quick remote Receive Byte queries. A B t LOW t HIGH C D n THIGH and TLOW registers are set to max and min limits, respectively Thermal Shutdown Signal When the temperature of DX1 reaches or exceeds the Tcrit1 threshold consecutively for the times equal to the number of faults of the FQ_TH_SHUT registers, TH_SHUT pin becomes logic high. The same mechanism is duplicated for DX2. There fore, either one of DX1, DX2 continuously over their respective Tcrit, the TH_SHUT will assert logic high to indicate a thermal shutdown event. G E F H I J K M L SMBCLK SMBDATA tS U:STA t HD:STA t HD:DAT t SU :DAT tS U:STO t BUF J K Figure 6. SMBus Write Timing Diagram A = start condition B = MSB of address clocked into slave C = LSB of address clocked into slave D = R / W bit clocked into slave E = slave pulls SMB Data line low F = acknowledge bit clocked into master G = MSB of data clocked into slave A B tLOW tHIGH C H = LSB of data clocked into slave I = slave pulls SMBDATA line low J = acknowledge clocked into master K = acknowledge clocked pulse L = stop condition data executed by slave M = new start condition D E F G H I SMBCLK SMBDATA t SU:STA t HD :STA t SU:DAT t SU:STO tBUF Figure 7. SMBus Read Timing Diagram A = start condition B = MSB of address clocked into slave C = LSB of address clocked into slave D = R / W bit clocked into slave E = slave pulls SMBDATA line low F =acknowledge bit clocked into master Rev.2.01 6/06/2003 G = MSB of data clocked into master H = LSB of data clocked into master I = acknowledge clocked pulse J = stop condition K= new start condition www.SiliconStandard.com 15 of 16 SS8017 Physical Dimensions C E1 E L D θ 7¢ X (4X) Taping Specification A2 e y A A1 b Feed Direction Note: Typical SSOP Package Orientation 1. Package body sizes exclude mold flash and gate burrs 2. Dimension L is measured in gage plane 3. Tolerance 0.10mm unless other wise specified 4. Controlling dimension is millimeter converted inch dimensions are not necessarily exact. MIN DIMENSION IN MM NOM MAX MIN DIMENSION IN INCH NOM MAX A 1.35 1.60 1.75 0.053 0.064 0.069 A1 0.10 ----- 0.25 0.004 ----- 0.010 A2 ----- 1.45 ----- ----- 0.057 ----- b 0.20 0.25 0.30 0.008 0.010 0.012 C 0.19 ----- 0.25 0.007 ----- 0.010 D 4.80 ----- 5.00 0.189 ----- 0.197 E 5.80 ----- 6.20 0.228 ----- 0.244 E1 3.80 ----- 4.00 0.150 ----- 0.157 e ----- 0.64 ----- ----- 0.025 ----- L 0.40 ----- 1.27 0.016 ----- 0.050 y ----- ----- 0.10 ----- ----- 0.004 ? 0º ----- 8º 0º ----- 8º SYMBOLS Information furnished by Silicon Standard Corporation is believed to be accurate and reliable. However, Silicon Standard Corporation makes no guarantee or warranty, express or implied, as to the reliability, accuracy, timeliness or completeness of such information and assumes no responsibility for its use, or for infringement of any patent or other intellectual property rights of third parties that may result from its use. Silicon Standard reserves the right to make changes as it deems necessary to any products described herein for any reason, including without limitation enhancement in reliability, functionality or design. No license is granted, whether expressly or by implication, in relation to the use of any products described herein or to the use of any information provided herein, under any patent or other intellectual property rights of Silicon Standard Corporation or any third parties. Rev.2.01 6/06/2003 www.SiliconStandard.com 16 of 16