aSC7511 LOW-VOLTAGE 2-WIRE DIGITAL TEMPERATURE SENSOR WITH THERMAL ALARM PRODUCT SPECIFICATION Fully Released Specification Product Description Pin Configuration The aSC7511 is a high-precision CMOS temperature sensor with SMBus compatible serial digital interface, intended for use in PC thermal management applications. The aSC7511 can measure temperature of a remote thermal diode to an accuracy of ±1°C. Internal temperature can be measured to ±3°C. SOP-8 and MSOP-8 VDD 1 8 SCL Communication of configuration, temperature and alarm status takes place over the PC standard System Management Bus (SMBus). D+ 2 7 SDA The aSC7511 features thermal alarm functions with a user- D- 3 programmable trip and turn-off temperatures. The THERM output comparator can be set to control a fan while THERM aSC7511 6 ALERT / THERM2 4 5 GND ALERT signals that the remote or local temperature is outside of a range of temperatures. ALERT pin may be optionally configured as a second THERM output, THERM2 , controlling a second fan. The aSC7511 is available in SOP-8 and MSOP-8 surface mount packages. Application Diagram Features • • • • • • • • • Local and remote temperature sensors 0.25°C resolution, ±1°C accuracy on remote diode 1°C resolution, ±3°C accuracy on local sensor Extended temperature measurement range 0°C to +127°C (default) or –55°C to +150°C 2-wire SMBus serial interface with SMBus alert Programmable over / under temperature limits Offset registers for system calibration One or two over-temperature fail-safe THERM outputs 8-lead, Pb-free, SOIC (SOP) or MSOP package 3.3V 1 2 3 CPU aSC7511 SMBus Interface SDA SCL 4 THERM 7 8 6 ALERT / THERM2 Applications Desktop Computers – Motherboards and Graphics Cards Laptop Computers Ordering Information Part Number Package Temperature Range and Operating Voltage Marking How Supplied aSC7511D8 8-Lead SOP -40°C to +125°C, 3.3V aSC7511 Ayww 2500 units Tape & Reel aSC7511M8 8-Lead MSOP -40°C to +125°C, 3.3V 7511 Ayww 2500 units Tape & Reel Ayww – Assembly site, year, workweek © Andigilog, Inc. 2006 -1www.andigilog.com August 2006 - 70A04010 aSC7511 Absolute Maximum Ratings1 Parameter Rating Supply Voltage, VD D , 3.3V nom. -0.3, +3.6V Output Voltage VD D + 0.5V Notes: -0.3V to VD D + 0.5V D+ D- to GND -0.3V to 0.6V SDA, SCL, ALERT , THERM -0.3V to 5.5V I/O Current, SCL, SDA, -1mA ALERT , THERM Input Current, D- ±1mA Continuous Current, any other terminal 10mA Storage Temperature Range -60°C to +150°C IR Reflow Peak Temperature 260°C Lead Soldering Temperature (10 sec.) 300°C ESD2 Human Body Model > 2000 V Machine Model > 250 V Charged Device Model > 2000 V 1. Absolute maximum ratings are limits beyond which operation may cause permanent damage to the device. These are stress ratings only; functional operation at or above these limits is not implied. 2. Human Body Model: 100pF capacitor discharged through a 1.5kΩ resistor into each pin. Machine Model: 200pF capacitor discharged directly into each pin. Charged Device Model is per JESD22-C101C. 3. These specifications are guaranteed only for the test conditions listed. 4. Accuracy (expressed in °C) = Difference between the aSC7511 reported output temperature and the temperature being measured. 5. Guaranteed by characterization but not production tested. 6. The accuracy of the aSC7511 is guaranteed when using the thermal diode of a processor or any thermal diode with a non-ideality of 1.008 and internal series resistance of 3.52Ω. When using a 2N3904 type transistor as a thermal diode the error band will be typically shifted depending on transistor characteristics. 7. The aSC7511 can be read at any time without interrupting the temperature conversion process. Electrical Characteristics3 (-40°C ≤ T A ≤ +125°C, V D D = 3 . 3 V unless otherwise noted. Specifications subject to change without notice) Parameter Conditions Supply Voltage VDD 3.0 Local Sensor Accuracy4 IDD Typ Max 3.3 3.6 V 215 µA 6 10 µA Standby Mode, +85°C ≤ T A ≤ +120°C 6 20 µA -40°C ≤ T A ≤ +100°C, 3V≤ V D D ≤ 3.6V ±1 ±3 °C Standby Mode, -40°C ≤ T A < +85°C Local Sensor Resolution 1 4,5,6 Remote Sensor Accuracy Units 170 0.0625 Conversions-per-second rate Operating Supply Current Min +60°C ≤ T A ≤ +100°C, -55°C≤TD ≤+150°C, 3V≤VDD≤3.6V ±1 -40°C ≤ T A ≤ +120°C, -55°C≤TD ≤+150°C, 3V≤VDD≤3.6V Remote Sensor Resolution °C ±2 °C ±3 °C 0.25 °C Temperature Conversion Time7 From Stop Bit to Conversion Complete, One-Shot Mode, 2 Sensors, Averaging On 115 ms Temperature Conversion Time7 One-Shot Mode, Averaging Off 30 ms © Andigilog, Inc. 2006 -2www.andigilog.com August 2006 - 70A04010 aSC7511 Logic Electrical Characteristics (TA = 25 °C, VDD = 3.3V unless otherwise noted) Parameter Symbol Conditions Min Input Voltage Logic High VIH 3V≤ V D D ≤ 3.6V 2.1 Input Voltage Logic Low VIL 3V≤ V D D ≤ 3.6V 0.8 V VOL VDD=3.6V, IOL= -6mA 0.4 V IOL ALERT or THERM forced to 0.4V IIN VIN = 0V or 5.5V, -40°C ≤ T A ≤ +125°C SMBus Output Sink Current IOL TA = 25 °C, VOL = 0.6V SMBus Logic Input Current IIH, IIL Output Voltage Logic Low ( ALERT and THERM ) Output Low Sink Current ( ALERT and THERM ) Input Leakage Current Output Leakage Current Max Units V 1 mA ±1.0 µA 6 mA -1 0.1 +1 µA 1 µA IOH VOH = VDD = 3.6V tF CL= 400pF, IOL = -3mA 250 ns CIN All Digital Inputs 5 pF Output Transition Time Input Capacitance Typ Serial Port Timing (TA = 25 °C, VDD = 3.3V unless otherwise noted, Guaranteed by design, not production tested) Parameter Symbol Min Typ Max Units SCL Operating Frequency fSCL 400 kHz SCL Clock Transition Time tT:LH , tT:HL 300 ns μs SCL Clock Low Period tLOW 1.3 SCL Clock High Period tHIGH 0.6 Bus free time between a Stop and a new Start Condition tBUF 1.3 μs Data in Set-Up to SCL High tSU:DAT 100 ns Data Out Stable after SCL Low tHD:DAT 300 ns SCL Low Set-up to SDA Low (Repeated Start Condition) tSU:STA 600 ns SCL High Hold after SDA Low (Start Condition) tHD:STA 600 ns SDA High after SCL High (Stop Condition) tSU:STO 600 Time in which aSC7511 must be operational after a power-on reset tPOR SCL tHD:STA tBUF tSU:DAT tLOW tHIGH μs ns 500 ms tSU:STA tSU:STO tT:HL tT:LH 90 10 SCL 50 90 10 SDA Data Out © Andigilog, Inc. 2006 tHD:DAT -3www.andigilog.com August 2006 - 70A04010 aSC7511 Pin Descriptions Pin # Name Direction 1 VDD 2 D+ 3 D- Supply Current Source Current Sink 4 THERM Output 5 GND Supply 6 ALERT / THERM2 Output 7 8 Description Supply Voltage Remote Diode Anode or Positive Lead Remote Diode Cathode or Negative Lead Open-drain logic output that may be used to control a fan or throttle CPU when programmed temperature limit is exceeded. Ground Open-drain logic output used as a mask-able interrupt or SMBus alert. Configurable as second THERM output. SDA Input/Output Serial Data—Open drain I/0-data pin for two-wire serial interface. SCL Input Serial Clock—Clock for two-wire serial interface. Note: Open-drain pins require a pull-up resistor. Conversion Rate Local Sensor Address Pointer Remote Low Limit Local Temp. D+ D- Remote High Limit Remote THERM Limit Comparator ADC 2 3 Local Low Limit Remote Temp. Local High Limit Local THERM Limit Busy Remote Offset Remote Diode Open Status Configuration SMBus Interface Mask 1 5 VDD VSS 7 SDA 8 SCL 4 THERM 6 ALERT / THERM2 Figure 1. Block Diagram © Andigilog, Inc. 2006 -4www.andigilog.com August 2006 - 70A04010 aSC7511 Basic Operation Overview The aSC7511 temperature sensing circuitry continuously monitors two thermal diode base-emitter voltages, one onchip, called “local” and one remotely located, connected to the D+ and D- pins. At regular intervals the aSC7511 converts both analog voltages to digital values, which are placed into the temperature registers. The aSC7511 has an SMBus-compatible serial interface that allows the user to access the data in the temperature registers at any time. In addition, the serial interface gives the user easy access to all other aSC7511 registers to customize operation of the device. Digital Output (Offset Binary) Temperature The aSC7511 has a Shutdown Mode that reduces the operating current to < 20µA. This mode is controlled by RUN / STOP, bit 6 in the configuration register. Comparisons to limits and diode open test are suspended until the next measurement has taken place. Low Byte Always Zero Local Sensor Remote Sensor The aSC7511 temperature-to-digital converter has two temperature formats, 0°C to +127°C binary and extendedrange, -55°C to +150°C, offset-binary. The local sensor resolution is 8-bits, with an LSB of 1°C. The remote or remote diode sensor resolution is 10-bits with an LSB of 0.25°C. The temperature range of the local and remote sensors are controlled by bit 2 of the configuration register, default value is 0, 0°C to 127°C. Table 1 gives examples of the relationship between the output digital data and the measured temperature for the default range. Table 2 gives examples for the extended range. All output values are offset by +64°C when in this mode. High Byte 8-Bit Resolution 00 10-Bit Resolution 00 0000 00 0000 +150°C 1101 0110 00 00 0000 +127°C 1011 1111 00 00 0000 +125°C 1011 1101 00 00 0000 +100°C 1010 0100 00 00 0000 +50°C 0111 0010 00 00 0000 +25°C 0101 1001 00 00 0000 +10°C 0100 1010 00 00 0000 +1.75°C 0100 0001 11 00 0000 +0.25°C 0100 0000 01 00 0000 0°C 0100 0000 00 00 0000 -55°C 0000 1001 00 00 0000 Table 2. Relationship Between Temperature and Digital Output, Extended Range, -55°C to +150°C Power-Up Default Conditions The aSC7511 always powers-up in the following default state: • Configuration Register: 00h (i.e., ALERT enabled, Run Mode, ALERT pin selected, normal range) Digital Output (Binary) Temperature High Byte Low Byte Always Zero Local Sensor Remote Sensor 8-Bit Resolution 00 10-Bit Resolution 00 0000 00 0000 • Conversion Rate: 16 per second, 08h • All Temperature and Offset Registers: 00h • Consecutive ALERT : 1 fault (i.e., 01h in the register) >127°C 0111 1111 00 00 0000 +127°C 0111 1111 00 00 0000 +125°C 0111 1101 00 00 0000 +100°C 0110 0100 00 00 0000 +50°C 0011 0010 00 00 0000 • THERM Hysteresis: 10°C +25°C 0001 1001 00 00 0000 +10°C 0000 1010 00 00 0000 • Register Address Pointer: Undefined, must be set by first write sequence. +1.75°C 0000 0001 11 00 0000 +0.25°C • Normal / Extended Range: Normal 0000 0000 01 00 0000 0°C 0000 0000 00 00 0000 < 0°C 0000 0000 00 00 0000 • Local and Remote Low Limit: 0°C • Local and Remote THERM Limit: 85°C After power-up, these conditions can be reprogrammed via the serial interface. Refer to the Serial Data Bus Operation section to for aSC7511 programming instructions. Table 1. Relationship Between Temperature and Digital Output, Default Range, 0°C to +127°C © Andigilog, Inc. 2006 -5www.andigilog.com August 2006 - 70A04010 aSC7511 Temperature Measurement The aSC7511 measures temperature by calculating the change in sensing a diode-connected transistor’s baseemitter voltage (ΔVBE) when two different currents are applied sequentially. This difference has a linear positive slope with temperature, unlike the non-linear VBE under a constant current. The ΔVBE is amplified and scaled depending on the type of transistor being measured. The typical case for the remote measurement is to connect to the substrate thermal diode of a CPU or ASIC. This will provide the die temperature of that device to a high level of accuracy for the purpose of controlling system cooling or reporting routine or overtemperature conditions. For each measurement cycle, an internal 2:1 multiplexer alternates between the local and remote sensor diodes and provides the input to a filter and amplifier. An analog-todigital converter takes this signal, converts it to a digital value and stores the alternating values in the appropriate temperature register of the aSC7511. These stored values are continuously compared to several user-selected limit values for sending alarm conditions or turning on an external fan driver. Conversions for both sensors will proceed automatically at the default rate of 16 conversions per second until a different rate is selected or one-shot or stand-by mode are selected. The conversion rate is user-selected by writing to the conversion rate register. Table 3 provides a list of conversion rates ranging from 0.0625 to 64 conversions per second. Sensor power consumption is directly proportional to the conversion rate and should be taken into account in power-limited applications as well as the impact that power dissipation has in self-heating of the local sensor. More details are provided in the Operation section. Note that limit comparisons are triggered only by a measurement action, not by a change in limits. An actual alarm condition may exist but will not be reported until a measurement takes place. This should be taken into account when using slow conversion rates. The ALERT pin may also be configured as a second THERM pin, THERM2 . This will behave in the same way as the THERM pin, but will be controlled by the high limit used for the ALERT pin, although it will not need to be reset by the master and does not use the hysteresis value. A more detailed discussion and examples is provided in the Operation section. Fault Tolerance The number of out of limit readings required before the ALERT is asserted may be set by writing to the Consecutive ALERT register. The default value is 1 and the user may select requiring 2, 3, or 4 consecutive out of limit readings before is ALERT asserted. Registers The ASC7511 contains 22 8-bit registers. All of these registers may be accessed by the user via the digital serial interface at any time. A detailed description of these registers and their functions is provided in the following paragraphs. Reading and writing to registers is covered in the SMBus Operation section. Use of the register set to control and interrogate the aSC7511 is covered in the Operation section. A table of the registers is provided in Table 4. Address Pointer Register Thermal Alarm and Alert Functions The Address Pointer Register is a write-only register that is The aSC7511 thermal alarm function, THERM , provides user programmable thermostat capability and allows the aSC7511 to function as a standalone thermostat without constant attention over the serial interface. This signal is an open drain output. When either the remote or local temperature reading exceeds the selected limits it goes low and will remain low until the measured temperature falls automatically written by the first byte that follows the R/ W bit of a write transaction. If R/ W is low, It will then contain the address to which the following byte is written, when R/ W bit is high it will be the read address. Details of the reading and writing sequence are covered in the Serial Interface Operation section. below the alarm limit by the amount set into the THERM hysteresis register (default value is 10°C). Measured Temperature Value Registers The aSC7511 thermal alert function, ALERT , provides another open-drain pin that is driven low when either the internal or remote temperature is greater than the high limit or less than or equal to the low limit selected by the user. In addition, an SMBus Alert is generated, requiring the bus master to inquire on the SMBus which client has The aSC7511 has two sensors whose measured values are stored in registers. Remote temperature is two bytes, at register addresses 01h and 10h. Local temperature is at 00h. The power-on default values are zero and the aSC7511 will automatically begin filling these registers with values after the power on reset sequence is complete. These are read-only registers. interrupted in order to re-set the alert. The ALERT pin may be masked by the user with bit 7 of the configuration register. © Andigilog, Inc. 2006 -6www.andigilog.com August 2006 - 70A04010 aSC7511 Status Register The status register is a read-only register for reporting the state of the aSC7511’s alarms. It is a read-only register located at 02h. When any high or low local limits or high or low remote limits are exceeded, bits 3 through 6 are set accordingly Bit Name Function 0 LTHERM Local sensor > THERM limit 1 RTHERM Remote sensor > THERM limit 2 ROPEN Remote sensor open-circuit 3 RLOW Remote sensor ≤ low limit the ALERT pin will remain asserted until the master has serviced the SMBus alert. 4 RHIGH Remote sensor > high limit 5 LLOW Local sensor ≤ low limit The local and remote THERM limit trip are reported in bits 0 and 1 respectively. These two bits are reset only by the 6 LHIGH Local sensor > high limit 7 BUSY Converter in process of conversion and the ALERT pin 6 will be driven low. If the remote sensor is open-circuit, bit 2 will be set and the ALERT will be asserted. Reading the status register will re-set these flags if the alerted condition has been removed, however, temperature falling below the THERM limit by the amount set into the hysteresis register. Table 3. Status Register Bit Assignments Bit 7 will be high when the converter is busy. The list of status register bit assignments is in Table 3. Each condition is asserted when the bit is high. Default is 0. Read Write Address Address n/a n/a Default Value Description Address Pointer Default Value Description n/a 00h / 0°C 2 00h n/a Local Temperature (high-byte) 01h n/a Remote Temperature (high-byte) 02h n/a Status n/a 03h 09h Configuration 00h 04h 0Ah Conversion rate 08h 05h 0Bh Local High Limit 55h / 85°C 06h 0Ch Local Low Limit 07h Read Write Address Address 2 00h 2 10h n/a Remote Temperature (low-byte) 13h 13h Remote High Limit (low-byte) 14h 14h Remote Low Limit (low-byte) 2 12h 12h Remote Temp. Offset (low-byte) 00h / 0°C 00h / 0°C 55h / 85°C 2 0Dh Remote High Limit (high-byte) 08h 0Eh Remote Low Limit (high-byte) 2 00h / 0°C n/a 0Fh One-Shot Measurement 11h 11h Remote Temp. Offset (high-byte) 19h 19h Remote THERM Limit 55h / 85°C 20h 20h Local THERM Limit 21h 21h THERM Hysteresis 55h / 85°C 0Ah / 10°C 22h 22h Consecutive ALERT 01h FEh n/a Manufacturer ID 61h 00h / 0°C 2 00h / 0°C n/a 2 00h / 0°C 2 00h / 0°C FFh n/a Die Revision Code 00h Notes: 1. Low-byte values are fractional degrees, MSB of lower byte is 0.5°C 2. Changing to extended range adds 64°C to values reported, but limit settings are not changed and must be corrected by the user. Table 4. aSC7511 Registers © Andigilog, Inc. 2006 -7www.andigilog.com August 2006 - 70A04010 aSC7511 Configuration Register 16 0.0625 The configuration register is a read-write register that 32 0.03125 09h stores the controls for masking the ALERT signal, RUN / STOP control, extended temperature range select and the 64 0.015625 0Ah Reserved Reserved 0Bh to FFh pin 6 function select for ALERT or THERM2 . It is located at address 03h for read and 09h for writing. Power on default is for all bits reset: no ALERT mask, RUN, pin 6 is ALERT and normal range, 0°C to 127°C. Table 5 lists the bits of the configuration register. The mask bit is only functional when pin 6 is configured as the ALERT pin. When selecting extended range, note that the values reported will be offset by 64°C and any limits will have to be adjusted accordingly to match this offset-binary coding. It is recommended that this configuration not be changed again, once selected, to avoid confusion. 08h Table 6. Conversion Rate Register Bit Assignments The conversion rate register may be written-to at address 04h. The value stored may be read back at any time from address 0Ah. The lower four bits define the rate from 0.0625 to 64 conversions per second. The default rate is 16 conversions per second designated by a code of 08h. The rates are described in Table 6. A single measurement is controlled separately by the oneshot register, 0Fh, that is described below. ALERT Limit Registers Bit 0, 1 2 3, 4 5 Name Function There are four limit registers for the ALERT function using six register locations: Reserved 0 = 0°C to +127°C Range Select • ALERT Remote High Limit (high and low bytes) 1 = -55°C to +150°C Reserved • ALERT Remote Low Limit (high and low bytes) ALERT / THERM2 6 RUN / STOP 7 MASK 0 = pin 6 is ALERT • ALERT Local High Limit 1 = pin 6 is THERM2 • ALERT Local Low Limit 0 = RUN 1 = STOP These registers may be written or read-back at any time at the addresses in shown in Table 2. Each limit has a default value at power-up of 85°C for the high limit and 0°C for the 0 = ALERT Enabled 1 = ALERT Masked Table 5. Configuration Register Bit Assignments Conversion Rate Register The sensor conversion rate register sets the rate of conversions. Both local and remote sensors are measured during a measurement cycle. Conversions per Second Seconds per Conversion Code low limit. The ALERT high limits have a dual purpose in that they may be used to control the alternate function of pin 6, the ALERT / THERM2 output when that mode is selected. Note that the values in the alarm registers must match the data format selected by bit 2, the normal / extended range selector in the configuration register. The user should choose either normal or extended range on power-up and not change this setting otherwise all limits will be invalid and have to be adjusted accordingly. Operation of these registers in thermal management applications is described in the Operation Section. 0.0625 16 00h 0.125 8 01h One-Shot Register While the aSC7511 is in standby mode with configuration register bit 6 high, a single measurement cycle may be initiated by a write to the one-shot register at address 0Fh. Any data written is ignored. After the conversion is completed a set of readings is written to the temperature registers, comparisons made and alerts generated. The aSC7511 will then return to standby mode, awaiting the 0.25 4 02h 0.5 2 03h 1 1 04h 2 0.5 05h 4 0.25 06h 8 0.125 07h © Andigilog, Inc. 2006 -8www.andigilog.com August 2006 - 70A04010 aSC7511 next one-shot reading or full activation. Standby mode is discussed further in the Operation section. Table 7. Offset Register Sample Codes Consecutive ALERT Register THERM Limit Registers This register will set the number of out of limit value There are two limit registers for the THERM function: readings it will require before ALERT is asserted. It is stored at register address 22h. The default value is for a single out of limit reading to assert ALERT . The register values for up to 4 out-of-limit readings are found in Table 8. • THERM Remote High Limit • THERM Local High Limit These registers may be written or read-back at any time at the addresses in shown in Table 2. Both limits has a default value at power-up of 85°C. Number of Out-of-Limit Measurements Required Register Value 1 yxxx 000x 2 yxxx 001x 3 yxxx 011x 4 yxxx 111x The THERM alarm will be set when this limit is exceeded and will reset when the temperature falls below that limit. However, there is also a THERM hysteresis register that may be used to set the temperature difference below x = Don’t Care y = SMBus Timeout Enable the THERM limit setting where the THERM alarm will be reset once it has been triggered. This value is defaulted to 10°C and may be set to any value after power-on. Operation of these registers in thermal management applications is described in the Applications Section. This register is also used to control activation of the SMBus timeout feature. It is disabled by default and enabled by writing a 1 to the MSB, bit 7. Remote Sensor Offset Register Manufacturer’s Registers Offset errors may be encountered on the remote sensor readings caused by factors such as system clock noise induced into the sensor interconnect or by a difference between the measured temperature and the actual temperature of interest in the system. A correction offset value may be provided by the user to add or subtract from the measured value resulting in a corrected value being stored in the remote temperature registers. The limit values will then be compared to these corrected values. Manufacturer’s identification is stored in the register at address FEh and set to the value 61h. Register FFh contains the die revision code. The offset register coding is two’s complement and it is allocated two bytes at addresses 11h and 12h. Table 7 describes some examples of values in the range from 128°C to +127.75°C that may be applied. Offset Value Offset Register High Byte (11h) Offset Register Low Byte (11h) +127.75°C 0111 1111 11 00 0000 +4°C 0000 0100 00 00 0000 +1°C 0000 0001 00 00 0000 +0.5°C 0000 0000 10 00 0000 0°C 0000 0000 00 00 0000 -0.5°C 1111 1111 10 00 0000 -1°C 1111 1111 00 00 0000 -4°C 1111 1100 00 00 0000 -128°C 1000 0000 00 00 0000 © Andigilog, Inc. 2006 Table 8. Consecutive Alert Register Serial Data Bus Operation General Operation Writing to and reading from the aSC7511 registers is accomplished via the SMBus-compatible two-wire serial interface. SMBus protocol requires that one device on the bus initiate and control all read and write operations. This device is called the “master” device. The master device also generates the SCL signal that is the clock signal for all other devices on the bus. All other devices on the bus are called “slave” devices. The aSC7511 is a slave device. Both the master and slave devices can send and receive data on the bus. During SMBus operations, one data bit is transmitted per clock cycle. All SMBus operations follow a repeating nine clock-cycle pattern that consists of eight bits (one byte) of transmitted data followed by an acknowledge (ACK) or not acknowledge (NACK) from the receiving device. Note that there are no unused clock cycles during any operation— therefore there must be no breaks in the stream of data and ACKs / NACKs during data transfers. For most operations, SMBus protocol requires the SDA line to remain stable (unmoving) whenever SCL is high — i.e. -9www.andigilog.com August 2006 - 70A04010 aSC7511 any transitions on the SDA line can only occur when SCL is low. The exceptions to this rule are when the master device issues a start or stop condition. Note that the slave device cannot issue a start or stop condition. register’s content is automatically set to the value of the The aSC7511 supports packet error checking (PEC) per the SMBus protocol. It will interpret the PEC byte when provide and respond with a PEC byte when expected by the master. The PEC byte is calculated using CRC-8 and conforms to the frame check sequence with the polynomial: the address and R/ W bit, the master device must transmit an appropriate 8-bit address pointer value as explained in the Registers section of this data sheet. The aSC7511 will send an ACK after receiving the new pointer data. first byte following the R/ W bit being set to 0. After the aSC7511 sends an ACK in response to receiving SMBus Definitions The register address pointer set operation is illustrated in Figure 2. If the address pointer is not a valid address the aSC7511 will internally terminate the operation. Also recall that the address register retains the current address pointer value between operations. Therefore, once a register is being pointed to, subsequent read operations do not require another Address Pointer set cycle. The following are definitions for some general SMBus terms: Writing to Registers C(x) = x8 + x2 + x1 + 1 Refer to SMBus specification 2.0 for more details. Start Condition: This condition occurs when the SDA line transitions from high to low while SCL is high. The master device uses this condition to indicate that a data transfer is about to begin. All writes must start with a pointer set as described previously, even if the pointer is already pointing to the desired register. The sequence is described in Figure 3. Stop Condition: This condition occurs when the SDA line transitions from low to high while SCL is high. The master device uses this condition to signal the end of a data transfer. Immediately following the pointer set, the master must begin transmitting the data to be written. After transmitting each byte of data, the master must release the SDA line for one clock to allow the aSC7511 to acknowledge receiving the byte. The write operation should be terminated by a stop condition from the master. Acknowledge and Not Acknowledge: When data are transferred to the slave device it sends an “acknowledge” (ACK) after receiving each byte. The receiving device sends an ACK by pulling SDA low for one clock. Following the last byte, a master device sends a "not acknowledge" (NACK) followed by a stop condition. A NACK is indicated by forcing SDA high during the clock after the last byte. Slave Address Each slave device on the bus has a unique 7-bit SMBus slave address. The aSC7511’s slave address is 4C hex. Writing to and Reading from the aSC7511 All read and write operations must begin with a start condition generated by the master device. After the start condition, the master device must immediately send a slave address (7-bits) followed by a R/ W bit. If the slave address matches the address of the aSC7511, it sends an ACK by pulling the SDA line low for one clock. Read or write operations may contain one- or two-bytes. See Figures 2 through 6 for timing diagrams for all aSC7511 operations. Setting the Register Address Pointer For all operations, the address pointer stored in the address pointer register must be pointing to the register address that is going to be written to or read from. This © Andigilog, Inc. 2006 Reading from Registers To read from a register other than the one currently being pointed to by the address pointer register, a pointer set sequence to the desired register must be done as described previously. Immediately following the pointer set, the master must perform a repeat start condition that indicates to the aSC7511 that a read is about to occur. It is important to note that if the repeat start condition does not occur, the aSC7511 will assume that a write is taking place, and the selected register will be overwritten by the upcoming data on the data bus. The read sequence is described in Figure 4. After the start condition, the master must again send the device address and read/write bit. This time the R/ W bit must be set to 1 to indicate a read. The rest of the read cycle is the same as described in the previous paragraph for reading from a preset pointer location. If the pointer is already pointing to the desired register, the master can read from that register by setting the R/ W bit (following the slave address) to a 1. After sending an ACK, the aSC7511 will begin transmitting data during the following clock cycle. After receiving the 8 data bits, the master device should respond with a NACK followed by a stop condition. If the master is reset while the aSC7511 is in the process of being read, the master should perform an SMBus reset. This is done by holding the data or clock low for more than - 10 www.andigilog.com August 2006 - 70A04010 aSC7511 35ms, allowing all SMBus devices to be reset. This follows the SMBus 2.0 specification of 25-35ms. 1 9 1 A A7 When the aSC7511 detects an SMBus reset, it will prepare to accept a new start sequence and resume communication from a known state 9 SCL SDA S 1 0 0 1 1 0 R/W 0 Start A6 ACK from aSC7511 SMBus Device Address Byte (4Ch) A5 A4 A3 A2 A1 A0 A ACK from aSC7511 Register Address Byte Stop By Master Figure 2. Register Address Pointer Set 1 9 1 A A7 9 1 A D7 9 SCL SDA S 1 0 0 1 1 0 0 R/W Start SMBus Device Address Byte (4Ch) A6 ACK from aSC7511 A5 A4 A3 A2 A1 A0 D6 ACK from aSC7511 Register Address Byte D5 D4 D3 D2 D1 Register Data Byte D0 A ACK from aSC7511 Stop by Master Figure 3. Register Write 1 Register Address Pointer Set + (Figure 2.) without stop by Master S 1 0 0 1 1 0 0 R/W Re-start 9 1 A D7 9 D6 D5 D4 D3 D2 ACK from SMBus Device Address Byte (4Ch) aSC7511 Register Data Byte D1 D0 N NACK from Master Stop by Master Figure 4. Register Read 1 9 1 A D7 9 SCL SDA S 1 0 0 1 1 0 0 R/W Start SMBus Device Address Byte (4Ch) D6 ACK from aSC7511 D5 D4 D3 D2 D1 D0 N NACK from Master Register Data Byte Stop by Master Figure 5. Register Read When Read Address Already Set 1 9 1 A 1 9 SCL SDA S 0 0 0 1 1 0 0 R/W Start SMBus Alert Response Address Byte (0Ch) ACK from aSC7511 0 0 1 1 0 0 aSC7511 SMBus Address 1 N NACK from Master Stop by Master Figure 6. SMBus Alert Response © Andigilog, Inc. 2006 - 11 www.andigilog.com August 2006 - 70A04010 aSC7511 Operation Alarm Outputs The aSC7511 has two alarm functions, ALERT and THERM . THERM has a high temperature limit and ALERT has both high and low limits and will also respond to a remote diode open circuit failure. These limits are settable separately for the local and remote sensors. Any alarm condition is reported individually in the status register and may be read at any time on the SMBus. Alarm conditions are logically combined and used to drive two open-drain outputs, the ALERT output, (pin 6) and THERM output, (pin 4). Output pins may be used as an interrupt signal the CPU or to turn on remote drivers for fans or indicators. The ALERT pin will remain asserted until it has been reset by the host via the SMBus. The THERM pin will remain asserted until the temperature falls below the alarm level by the amount set into the THERM hysteresis register. ALERT Limits Figure 7 shows use of the ALERT high and low limits. The user sets up the alarm by writing the upper and lower limit temperatures into the limit registers over the SMBus. After each measurement, the comparator tests the readings against the programmed limits and if the measurement exceeds the high limit is or is equal to or less-than the low limit, it will assert the particular alarm bits will be reset, otherwise they will remain high until the conditions are no longer met and the register is read again. The same sequence applies to the local readings and limits. The ALERT pin will remain low until the status bits have been reset and an Alert Response has been issued by the master and responded by the aSC7511. This flow is described below. The user may mask-out or disable the ALERT signal pin should it be necessary to prevent a processor interrupt. This is controlled by setting bit 7 of the configuration register. SMBus Alert Output The ALERT pin may be used to signal an SMBus Alert to the host processor. This is a special mode of the SMBus interface that requires the SMBus host to send an Alert Response Address (ARA) to all slaves sharing the ALERT pin in order to isolate clear and service the alerting device. This sequence is described below and in Figure 6. The sequence of servicing this interrupt is as follows: 1. SMBALERT is asserted by the aSC7511 driving pin 6 low. 2. The SMBus master begins a read operation with a start followed by the ARA response address, 0001 100. This is an SMBus General Call Address to be used only for requesting an alert response. The 3. The device providing the SMBALERT signal responds to this by providing an ACK followed by its own bus address, an aSC7511 will provide, 100 1100, with the LSB of the data byte set to 1. A NACK response is expected from all bits in the status register and cause the ALERT pin to go low. Conversion Ext. High ALERT Limit Temperature devices not giving an SMBALERT . Ext. Low ALERT Limit Status Bit-4, EXHIGH 4. If more than one device responds, the device with the lowest device address will have priority and will be serviced first by the master. 5. When the aSC7511 has responded with its own Status Bit-3, EXLOW Status Register Read address, it will de-assert the ALERT pin and the status register bit that caused it, if that condition ALERT Pin 6 and no other ALERT condition no longer exist. ARA Response THERM Limits Figure 7. ALERT Limits and Responses The status bits will remain high until the status register is read and then, if the condition is no longer present those © Andigilog, Inc. 2006 The THERM alarms operate differently from the alert alarms. THERM alarm status bits for remote and local - 12 www.andigilog.com August 2006 - 70A04010 aSC7511 limits, RTHERM and LTHERM, will change as soon as a reading is greater than the limit and will reset as soon as a reading goes below the limit minus the programmable hysteresis value. This hysteresis value applies to both remote and local sensors. The scenario is described in Figure 8. Standby Mode The aSC7511 may be placed in a minimum-power standby mode by writing a 1 to bit 6 of the configuration register. No measurements are made but the SMBus interface will respond when addressed. Any measurement in progress when standby is selected will be terminated and no new values will be written into the temperature registers. Conversion Ext. THERM Limit While in this mode, a one-shot measurement of both channels may be commanded by the user by writing any data value to the one-shot register, 0Fh. All alarm comparisons will continue to be made and reported. The alarm values may be changed while in standby and current measured temperatures will be compared and alarms generated if an out-of-limit condition exists. Temperature THERM Hysteresis Status Bit-1, EXTHERM THERM Pin 4 Operating current will be 10 μA or less when there is no activity on the SMBus and 100 μA or less when clock and data are active. Figure 8. THERM Limits and Responses The THERM limits default to 85ºC with 10ºC hysteresis. The hysteresis value may be set from 0ºC to any positive value up to 127ºC. All limit values must take into account whether measurements are being made in normal or extended range. In extended range, there is a 64ºC offset in reported values and limits must be adjusted accordingly. THERM2 Option The ALERT pin and associated alarm bits may be reassigned as a second THERM alarm. This alarm will work exactly like THERM . The ALERT mask will have no effect and there is only a high limit. The THERM hysteresis value is applied to this alarm. Applications Information Remote Diodes The aSC7511 is designed to work with a variety of remote sensors in the form of the substrate thermal diode of a CPU or graphics controller or a diode-connected transistor. Actual diodes are not suited for these measurements. There is some variation in the performance of these diodes, described in terms of its departure from the ideal diode equation. This factor is called diode nonideality, nf . The equation relating diode temperature to a change in thermal diode voltage with two driving currents is: Sensor Open Detect ΔVBE = (nf ) A protective circuit monitors the D+ pin for a voltage level that would indicate the path to the remote diode is open. If the voltage exceeds a typical value of VDD-1V, bit 2 of the status register and the ALERT flag are set and the ALERT pin is driven low. This will require the master to service the ALERT in order to reset the condition. If the remote diode is not being used, it is recommended that D+ and D- be shorted to prevent setting the open alarm. In the event that a remote diode open-circuit has caused an ALERT condition to occur and that condition is restored to normal, when the host sends an Alert Response and reads the Status Register the alert pin may not clear. To ensure that the ALERT pin clears, perform a read to internal register 42h. © Andigilog, Inc. 2006 KT ln(N ) q where: nf = diode non-ideality factor, (nominal 1.008). K = Boltzman’s constant, (1.38 x 10-23). T = diode junction temperature in Kelvins. q = electron charge (1.6 x 10-19 Coulombs). N = ratio of the two driving currents (16). The aSC7511 is designed and trimmed for an expected nf value of 1.008, based on the typical value for the Intel Pentium™ III and AMD Athlon™. There is also a tolerance on the value provided. The values for other CPUs and the 2N3904 may have different nominal values and tolerances. Consult the CPU or GPU manufacturer’s data sheet for the nf factor. Table 8 gives a representative sample of what one may expect in the - 13 www.andigilog.com August 2006 - 70A04010 aSC7511 range of non-ideality. The trend with CPUs is for a lower value with a larger spread. When thermal diode has a non-ideality factor other than 1.008 the difference in temperature reading at a particular temperature may be interpreted with the following equation: ⎛ 1.008 Tactual = Treported ⎜⎜ ⎝ nactual the CPU socket. The temperature indicated will need to be compensated for the departure from a non-ideality of 1.008. D+ CPU ⎞ ⎟ ⎟ ⎠ D- aSC7511 Substrate where: Figure 9. CPU Remote Diode Connection Treported = reported temperature in temperature register. Tactual = actual remote diode temperature. Series Resistance nactual = selected diode’s non-ideality factor, nf . Temperatures are in Kelvins or °C + 273.15. The temperature error caused by non-ideality difference is directly proportional to the difference from 1.008, but a small difference in non-ideality results in a relatively large difference in temperature reading. For example, if there were a ±1% tolerance in the non-Ideality of a diode it would result in a ±2.7 degree difference (at 0°C) in the result (0.01 x 273.15). This difference varies with temperature such that a fixed offset value may only be used over a very narrow range. Typical correction method required when measuring a wide range of temperature values is to scale the temperature reading in the host firmware. Any resistance in the connections from the aSC7511 to the CPU pins should be accounted for in interpreting the results of a measurement. The impact of series resistance on the measured temperature is a result of measurement currents developing offset voltages that add to the diode voltage. This is relatively constant with temperature and may be corrected with a fixed value in the offset register. To determine the temperature impact of resistance is as follows: ΔTR = RS × TV × ΔI D or, ΔTR = RS × 90 μ A = RS × 0.391°C / Ω 230 μV / °C where: Part nf Min Pentium™ III (CPUID 68h) 1.0057 1.008 1.0125 Pentium 4, 130nM 1.001 1.002 1.003 Intel Pentium M 1.0015 1.0022 1.0029 AMD Athlon™ Model 6 1.002 1.008 1.016 AMD Duron™ Models 7 and 8 1.002 1.008 1.016 AMD Athlon Models 8 and 10 1.0000 1.0037 1.0090 2N3904 1.003 1.0043 1.005 Pentium 4, 90nM nf Nom nf Max 1.011 Table 8. Representative CPU Thermal Diode and Transistor Non-Ideality Factors CPU or ASIC Substrate Remote Diodes A substrate diode is a parasitic PNP transistor that has its collector tied to ground through the substrate and the base (D-) and emitter (D+) brought out to pins. Connection to these pins is shown in Figure 13. The nonideality figures in Table 8 include the effects of any package resistance and represent the value seen from © Andigilog, Inc. 2006 ΔTR = difference in the temperature reading from actual. RS = total series resistance of interconnect (both leads). Δ I D = difference in the two diode current levels (90µA). TV = scale of temperature vs. VBE (230µV/°C). For example, a total series resistance of 10Ω would give an offset of +3.9°C. Discrete Remote Diodes When sensing temperatures other than the CPU or GPU substrate, an NPN or PNP transistor may be used. Most commonly used are the 2N3904 and 2N3906. These have characteristics similar to the CPU substrate diode with non-ideality around 1.003. They are connected with base to collector shorted as shown in Figure 14. While it is important to minimize the distance to the remote diode to reduce high-frequency noise pickup, they may be located many feet away with proper shielding. Shielded, twisted-pair cable is recommended, with the shield connected only at the aSC7511 end as close as possible to the ground pin of the device. As with the CPU substrate diode, the temperature reported will be subject to the same errors due to non- - 14 www.andigilog.com August 2006 - 70A04010 aSC7511 ideality variation and series resistance. However, the transistor’s die temperature is usually not the temperature of interest and care must be taken to minimize the thermal resistance and physical distance between that temperature and the remote diode. The offset and response time will need to be characterized by the user. Use ground runs along side the pair to minimize differential coupling as in Figure 14. 3. Place the aSC7511 as close to the CPU or GPU remote diode leads as possible to minimize noise and series resistance. 4. Avoid running diode connections close to or in parallel with high-speed busses, staying at least 2cm away. D- 5. Avoid running diode connections close to on-board switching power supply inductors. D+ 6. PC board leakage should be minimized by maintaining minimum trace spacing and covering traces over their full length with solder mask. D+ aSC7511 2N3906 2N3904 aSC7511 D- Figure 10. Discrete Remote Diode Connection Board Layout Considerations The distance between the remote sensor and the aSC7511 should be minimized. All wiring should be defended from high frequency noise sources and a balanced differential layout maintained on D+ and D-. Any noise, both common-mode and differential, induced in the remote diode interconnect may result in an offset in the temperature reported. Circuit board layout should follow the recommendation of Figure 15. Basically, use 10-mil lines and spaces with grounds on each side of the differential pair. Choose the ground plane closest to the CPU when using the CPU’s remote diode. 10 mils The temperature of the aSC7511 will be close to that of the PC board on which it is mounted. Conduction through the leads is the primary path for heat flow. The reported local sensor is very close to the circuit board temperature and typically between the board and ambient. In order to measure ambient air temperature, a remote diode-connected transistor should be used. A surfacemount SOT-23 or SOT-223 is recommended. The small size is advantageous in minimizing response time because of its low thermal mass, but at the same time it has low surface area and a high thermal resistance to ambient air. A compromise must be achieved between minimizing thermal mass and increasing the surface area to lower the junction-to-ambient thermal resistance. The power consumption of the aSC7511 is relatively low and should have little self-heating effect on the local sensor reading. At the highest measurement rate the dissipation is less than 2mW, resulting in only a few tenths of a degree rise. GND D+ 10 mils Thermal Considerations DGND Application Circuit Figure 11. Recommended Remote Diode Circuit Board Interconnect The aSC7511 may be used to turn a fan on and off in response to the internal or remote sensor. The active-low THERM pin offers a programmable turn-on temperature and the THERM hysteresis setting will turn the fan off. Noise filtering is accomplished by using a bypass capacitor placed as close as possible to the aSC7511 D+ and D- pins. A 2.2nF ceramic capacitor is recommended, but up to 3.3nF may be used. Additional filtering takes place within the aSC7511. An SMBus host is used to provide the settings It is recommended that the following guidelines be used to minimize noise and achieve highest accuracy: falls below THERM temperature by the amount set into 1. Place a 0.1µF bypass capacitor to digital ground as close as possible to the power pin of the aSC7511. 2. Match the trace routing of the D+ and D- leads and use a 2.2nF filter capacitor close to the aSC7511. © Andigilog, Inc. 2006 for THERM and THERM hysteresis. The fan will come on when the THERM limit is reached and will turn off when it the THERM hysteresis register. Figure 16 provides a circuit diagram. - 15 www.andigilog.com August 2006 - 70A04010 aSC7511 3.3V 5 V or 12V 0.1µF 2.2nF 1 2 CPU SMBus Host Interface 10kΩ 3 SDA SCL ALERT 7 8 4 aSC7511 THERM Fan Drive Circuit 6 5 Figure 12. Simple Fan Control Evaluation Board The aSC7511EVB provides a platform for evaluation of the operational characteristics of the aSC7511. The board features a graphical user interface (GUI) to control and monitor all activities and readings of the aSC7511. The provided software will run on a Windows™-based desktop or laptop PC with a DB-25 parallel printer port. Features: • Interactive GUI for setting limits and operational configuration • Powered and operated from PC parallel port • • • • • • • LEDs for THERM and ALERT signals Graphical readout of temperature and alarms Selectable NPN or PNP sensor transistors Selectable remote diode connector Log file of readings Saving of setting configurations Optional use of external power and SMBus © Andigilog, Inc. 2006 - 16 www.andigilog.com August 2006 - 70A04010 aSC7511 D8 Package – 8-Lead SOP Package Dimensions Pb-Free Package 7° 1.27mm BSC β 0.53mm 5.80mm (min) 6.20mm (max) 0.19mm (min) 0.25mm (max) 3.81mm (min) 3.99mm (max) 0.41mm (min) 1.27mm (max) 4.80mm (min) 4.98mm (max) 1.37mm (min) 1.57mm (max) 1.52mm (min) 1.72mm (max) 0.10mm (min) 0.25mm (max) Detail A 0.25mm (min) 0.50mm (max) x 45° 0.36mm (min) 0.46mm (max) α 0° (min) 8° (max) © Andigilog, Inc. 2006 - 17 www.andigilog.com August 2006 - 70A04010 Preliminary Specification – Subject to change without notice Preliminary Specification – Subject to change without notice Detail A aSC7511 M8 Package – 8-Lead MSOP Package Dimensions Pb-Free Package 9° (min) 15° (max) β 0.65mm BSC 0.525mm BSC Detail B 4.75mm (min) 5.05mm (max) 2.90mm (min) 3.10mm (max) α 0° (min) 6° (max) γ 0.25mm (min) 0.40mm (max) Section A 0° (min) 6° (max) 0.40mm (min) 0.70mm (max) 0.95mm BSC 0.13mm (min) 0.23mm (max) 0.13mm (min) 0.18mm (max) Detail B 2.85mm (min) 3.05mm (max) 0.25mm (min) 0.35mm (max) 0.78mm (min) 0.94mm (max) 1.10mm (max) 2.85mm (min) 3.05mm (max) A A 0.10m m 0.25mm (min) 0.40mm (max) 0.05mm (min) 0.15mm (max) 2.90mm (min) 3.10mm (max) © Andigilog, Inc. 2006 - 18 www.andigilog.com 2.90mm (min) 3.10mm (max) 4.75mm (min) 5.05mm (max) August 2006 - 70A04010 aSC7511 Data Sheet Classifications Preliminary Specification This classification is shown on the heading of each page of a specification for products that are either under development (design and qualification), or in the formative planning stages. Andigilog reserves the right to change or discontinue these products without notice. New Release Specification This classification is shown on the heading of the first page only of a specification for products that are either under the later stages of development (characterization and qualification), or in the early weeks of release to production. Andigilog reserves the right to change the specification and information for these products without notice. Fully Released Specification Fully released datasheets do not contain any classification in the first page header. These documents contain specification on products that are in full production. Andigilog will not change any guaranteed limits without written notice to the customers. Obsolete datasheets that were written prior to January 1, 2001 without any header classification information should be considered as obsolete and non-active specifications, or in the best case as Preliminary Specifications. ® Andigilog is a Registered Trademark of Andigilog, Inc. Pentium™ is a trademark of Intel Corporation Athlon™ and Duron™ are trademarks of AMD Corporation LIFE SUPPORT POLICY ANDIGILOG'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF ANDIGILOG, INC. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. Andigilog, Inc. 8380 S. Kyrene Rd., Suite 101 Tempe, Arizona 85284 Tel: (480) 940-6200 Fax: (480) 940-4255 © Andigilog, Inc. 2006 - 19 www.andigilog.com August 2006 - 70A04010