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smsc emc1023 datasheet revision 1.2 (04-15-05) datasheet emc1023 1c triple temperature sensor with resistance error correction general description the emc1023 is a system management bus (smbus) temperature sensor that is capable of monitoring three temperature zones. four unique part numbers can be ordered, each with a differ ent smbus address. the three temperature zones cons ist of two external diodes and one internal monitor. extended features include resistance error correction and ideality factor configuration eliminating both major sources of temperature measurement error. 1 the 11-bit delta-sigma temperature-to-digital converter provides superb linearity, excellent noise immunity and repeatable temperature readings. an extended temperature format may be se lected for compatibility with a broad range of cpus. selectable conversion rates and standby mode support low-power operation. features resistance e rror correction ideality factor configuration accepts 2200pf cap for noise suppression remote thermal zones ? 1 c accuracy (40 c to 80 c) ? 0.125 c resolution internal thermal zone ? 3 c accuracy (0 c to 85 c) ? 0.125 c resolution low power; 3.0v to 3.6v supply four unique smbus addresses available programmable conversion rate msop-8 3x3mm package; green, lead-free package also available. applications desktop and notebook computers thermostats smart batteries industrial/automotive 1.patents pending. simplified block diagram emc1023 local temp diode switching current smclk local temp register configuration register status register smbus interface remote temp register 1 remote temp register 2 smdata 11-bit delta-sigma adc analog mux dp1 dn1 dp2 dn2 digital mux and byte interlock
order numbers emc1023-1-aczb-tr for 8 pin, msop package (address - 1001100b) emc1023-2-aczb-tr for 8 pin, msop package (address - 1001101b) emc1023-3-aczb-tr for 8 pin, msop package (address - 1001000b) EMC1023-4-ACZB-TR for 8 pin, msop package (address - 1001001b) emc1023-1-aczl-tr for 8 pin, msop package (address - 1001100b) (green, lead-free) emc1023-2-aczl-tr for 8 pin, msop package (address - 1001101b) (green, lead-free) emc1023-3-aczl-tr for 8 pin, msop packag e (address - 1001000b) (green, lead-free) emc1023-4-aczl-tr for 8 pin, msop packag e (address - 1001001b) (green, lead-free) reel size is 4,000 pieces. evaluation board available upon request. (evb-emc1023) 80 arkay drive hauppauge, ny 11788 (631) 435-6000 fax (631) 273-3123 copyright ? smsc 2005. all rights reserved. circuit diagrams and other information relating to smsc products are included as a means of illustrating typical applications. consequently, complete information sufficient for construction purposes is not necessarily given. although the information has been checked and is bel ieved to be accurate, no responsibility is assumed for inaccuracies. smsc reserves the right to make changes to specifications and product descriptions at any time without notice. contact your local smsc sales office to obtain the latest specifications before placing your product order. the provisi on of this information does not convey to the purchaser of the described semiconductor devices any licenses under any patent rights or other intellectual p roperty rights of smsc or others. all sales are expressly conditional on your agreement to the terms and conditions of the most recently dated version of smsc's standard terms of sale agreement dated before the date of your order (the "terms of sale agreement"). the product may contain design def ects or errors known as anomalies which may cause the product's functions to de viate from published specifications. anomaly sheets are availab le upon request. smsc products are not designed, intended, authorized or warranted for use in any life support or other application where produc t failure could cause or contribute to personal injury or severe property damage. any and all such uses without prior written approval of an officer of smsc and furthe r testing and/or modification will be fully at the risk of the customer. copies of this document or other smsc literature, as wel l as the terms of sale a greement, may be obtained by visiting smsc?s website at http://www.smsc.com. smsc is a registered trademark of standard microsy stems corporation (?smsc?). product names and company names are the trademarks of their respective holders. smsc disclaims and excludes any and all warranties, including without limitation any and all implied warranties of merchantability, fitness for a particular purpose, title, and against infringement and the like, and any and all warranties arising from any course of dealing or usage of trade. in no event shall smsc be liable for any direct, incidental, indirect, special, punitive, or consequential damages; or for lost data, profits, savings or revenues of any kind; regardless of the form of action, whether based on contract; tort; negligence of smsc or others; strict liability; breach of warranty; or otherwise; whether or not any remedy of buyer is held to have failed of its essential purpose, and whether or not smsc has been advised of the possibility of such damages. 1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 2 smsc emc1023 datasheet
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 3 revision 1.2 (04-15-05) datasheet chapter 1 pin configuration figure 1.1 emc1023 pin configuration table 1.1 pin description pin pin no. description dp1 1 positive analog input for external temperature diode 1 dn1 2 negative analog input for external temperature diode 1 dp2 3 positive analog input for external temperature diode 2 dn2 4 negative analog input for external temperature diode 2 gnd 5 ground vdd 6 supply voltage smdata 7 system management bus data input/output, open drain output smclk 8 system management bus clock input emc1023 top view 8 7 6 5 1 2 3 4 dp1 dn1 dp2 dn2 smclk smdata vdd gnd
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 4 smsc emc1023 datasheet note: stresses above those listed could cause damage to the device. this is a stress rating only and functional operation of the device at any other condition above those indicated in the operation sections of this specification is not implied. when powering this device from laboratory or system power supplie s, it is important that the absolute maximum ratings not be exceeded or device failure can result. some power supplies exhibit voltage spikes on their outputs when the ac power is switched on or off. in addition, voltage transients on the ac power line may appear on the dc output. if this po ssibility exists, it is suggested that a clamp circuit be used. table 1.2 absolute maximum ratings description rating unit supply voltage v dd -0.3 to 5.0 v voltage on smdata and smclk pins -0.3 to 5.5 v voltage on any other pin -0.3 to vdd+0.3 v operating temperature range 0 to 85 c storage temperature range -55 to 150 c lead temperature range refer to jedec spec. j-std-020 package thermal characteristics for msop-8 power dissipation tbd thermal resistance (at 0 air flow) 135.9 c/w esd rating, all pins human body model 2000 v
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 5 revision 1.2 (04-15-05) datasheet chapter 2 electrical characteristics table 2.1 electrical characteristics v dd =3.0v to 3.6v, t a = 0 c to +85 c, typical values at t a = 27 c unless otherwise noted parameter symbol min typ max units conditions dc power supply voltage v dd 3.0 3.3 3.6 v average operating current i dd 36 42 a 1 conversions/s i pd 24 a standby mode internal temperature monitor temperature accuracy 1 3 c0 c t a 85 c temperature resolution 0.125 c external temperature monitor temperature accuracy remote diode 40 c to 80 c remote diode 0 c to 125 c 1 3 c c 15 c t a 70 c 0 c t a 85 c temperature resolution 0.125 c adc conversion time for all three sensors 62 ms wake-up from stop mode (during one shot command or transition to run mode) 1ms voltage tolerance (smdata,smclk) voltage at pin v tol -0.3 5.5 v smbus interface (smdata,smclk) input high level v ih 2.0 v input low level v il 0.8 v input high/low current i ih /i il -1 1 a hysteresis 500 mv input capacitance 5 pf output low sink current 6 ma smdata = 0.6v smbus timing clock frequency f smb 10 400 khz spike suppression 50 ns bus free time start to stop t buf 1.3 s hold time start t hd:sta 0.6 s
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 6 smsc emc1023 datasheet note 2.1 300ns rise time max is required for 400khz bus operation. for lower clock frequencies, the maximum rise time is (0.1/f smb )+50ns setup time start t su:sta 0.6 s setup time stop t su:sto 0.6 s data hold time t hd:dat 0.3 s data setup time t su:dat 100 ns clock low period t low 1.3 s clock high period t high 0.6 s clock/data fall time t f * 300 ns *min = 20+0.1c b ns clock/data rise time t r *300 note 2.1 ns *min = 20+0.1c b ns capacitive load (each bus line) c b 0.6 400 pf table 2.1 electrical char acteristics (continued) v dd =3.0v to 3.6v, t a = 0 c to +85 c, typical values at t a = 27 c unless otherwise noted parameter symbol min typ max units conditions
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 7 revision 1.2 (04-15-05) datasheet chapter 3 system management bus interface protocol a host controller, such as an smsc i/o controlle r, communicates with the emc1023 via the two wire serial interface named smbus. th e smbus interface is used to read and write registers in the emc1023, which is a slave-only device. a detailed timing diagram is shown in figure 3.1 . figure 3.1 system management bus timing diagram the emc1023 implements a subset of the smbus s pecification and supports write byte, read byte, send byte, receive byte, and alert response address protocols. as shown. in the tables that describe the protocol, the ?gray? columns indicate that the slave is driving the bus. 3.1 write byte the write byte protocol is used to write one byte of data to the registers as shown below: 3.2 read byte the read byte protocol is used to read one byte of data from the registers as shown below: 3.3 send byte the send byte protocol is used to set the internal address register to the correct address. the send byte can be followed by the receive byte protoc ol described below in order to read data from the register. the send byte protocol canno t be used to write data - if data is to be written to a register then the write byte protocol must be used as described in subsection above. the send byte protocol is shown in table 3.3, ?smbus send byte protocol,? on page 7 . table 3.1 smbus write byte protocol start slave address wr ack command ack data ack stop 171 18 18 11 table 3.2 smbus read byte protocol start slave address wr ack command ack start slave address rd ack data nack stop 171 18 11 7 1 1 81 1 table 3.3 smbus send byte protocol field: start slave addr wr ack reg. addr ack stop bits: 1711811 smdata smclk t low t r t high t f t buf t hd:sta p s s - start condition p - stop condition t hd:dat t su:dat t su:sta t hd:sta p t su:sto s
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 8 smsc emc1023 datasheet 3.4 receive byte the receive byte protocol is used to read data from a register when the internal register address pointer is known to be at the right location (e.g. se t via send byte). this can be used for consecutive reads of the same register as shown below: 3.5 smbus addresses the emc1023 may be ordered with one of four 7-bit slave addresses as shown in order numbers . attempting to communicate with t he emc1023 smbus interface with an invalid slave address or invalid protocol results in no response from the device an d does not affect its register contents. the emc1023 supports stretching of the smclk signal by ot her devices on the smbus but will not perform this operation itself. 3.6 smbus timeout the emc1023 includes an smbus timeout feature. fo llowing a 25 ms period of inactivity on the smbus, the device will timeout an d reset the smbus interface. table 3.4 smbus receive byte protocol field: start slave addr rd ack reg. data nack stop bits: 1711811
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 9 revision 1.2 (04-15-05) datasheet chapter 4 product description the emc1023 is an smbus sensor that is capable of monitoring three temperature zones for use in a personal computer or embedded environment. the part may be used as a companion to one of smsc?s broad line of sio host circuits, or other devices capable of performing the smbus host function. figure 4.1 system overview in cooperation with the host device, therma l management can be performed as outlined in figure 4.1 above. thermal management consists of the host read ing the temperature data from the remote and internal temperature diodes of the emc1023 and cont rolling the speed of one or multiple fans. since the emc1023 incorporates one internal and two exte rnal temperature diodes, three separate thermal zones can be monitored and controlled with this application. also, measured temperature levels can quickly be compared to preset limits within the host device which in turn will take the appropriate action when values are found to be out of limit. the emc1023 has two basic modes of operation: run mode: in this mode, the emc1023 continuou sly converts temperature data and updates its registers. the conversion rate is configured by the lower bits in the configuration register as described in section table 4.8, "configuration register, conversion rate," on page 14 . standby mode: in this mode, t he emc1023 is powered down, drawing a maximum current of only 3ua. the smbus is still operational and a one-s hot command can be given which will force the circuit to complete one full set of temperature conversions. the emc1023 will return to standby mode after the one shot conversion has finished. 4.1 temperature monitors thermal diode temperature measurements are bas ed on the change in forward bias voltage ( ? v be ) of a diode when operated at two different currents: the change in ? v be voltage is proportional to absolute temperature t. where: k = boltzmann?s constant t = absolute temperature in kelvin q = electron charge = diode ideality factor emc1023 host (smsc sio) smbus interface dp1 dn1 smbus internal diode dp2 dn2 ? ? ? ? ? ? ? ? = ? = ? low high low be high be be i i q kt v v v ln _ _
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 10 smsc emc1023 datasheet figure 4.2 detailed block diagram figure 4.2 shows a detailed block diagram of the temperature measurement circuit. the emc1023 incorporates switched capacitor technolog y that integrates the temperature diode ? v be from different bias currents. the negative terminal, dn, for the te mperature diode is internally biased with a forward diode voltage referenced to ground. the advantages of this architecture over nyquist rate flash or sar converters are superb linearity and inherent noise immunity. the linearity can be di rectly attributed to the delta-sigma adc single-bit comparator while the noise immunity is achieved by the ~20ms integration time which translates to 50hz input noise bandwidth. the 11 bit conversion can be displayed in either legacy format or in extended range format. in legacy format, the temperature range covers ?64oc to 127 oc while in extended format, temperature readings span -64oc to 191oc. it should be noted that the latt er range is really meant to cover thermal diodes with a non ideal curvature caused by factor n in equation (1) not being equal to exactly 1.000. in general, it is not recommended to run silicon ba sed thermal diodes at te mperatures above 150oc. 4.2 resistance error correction the emc1023 includes resistance error correction implemented in the analog front end of the chip. without this automatic f eature, voltage developed across the parasitic resistance in the remote diode path causes the temperature to read higher than the true zone temperatur e. the error introduced by parasitic resistance is approximately +0.7oc per ohm. sources of parasiti c resistance include bulk resistance in the remote temperature transistor junc tions along with resistance in the printed circuit board traces and package leads. resistance error correction in the emc1023 eliminat es the need to characterize and compensate for parasitic resistance in the remote diode path. 4.3 programmable idealit y factor configuration temperature sensors like the emc1023 are typically designed for remote diodes with an ideality factor of 1.008. when the diode does not have this exac t factor, an error is introduced in the temperature measurement. programmable offset registers are sometimes used to compensate for this error, but this correction is only perfect at one temperature since the error in troduced by ideality factor mismatch is a function of temperature. the higher the tem perature measured, the greater the error introduced. to provide maximum flexibility to the user, the emc1 023 provides a 6-bit ideality factor register for each remote diode. the ideality factor of the re mote diode is programmed in these registers to eliminate errors across all temperatures. see section 4.10, "ideality fa ctor register," on page 15 for details on programming these registers. delta vbe sample & hold i bias i low i high 1-bit delta-sigma modulator digital averaging filter v dd internal or remote diode bias diode 11-bit outpu t
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 11 revision 1.2 (04-15-05) datasheet 4.4 register allocation see table 4.1, ?register table,? on page 11 for a description of registers that are accessible through the smbus: during power on reset (por), the default values ar e stored in the registers. a por is initiated when power is first applied to the part and the vo ltage on the vdd supply surpasses the por level as specified in the electrical characte ristics. any reads to undefined regist ers will return 00h. writes to any undefined registers will not have an effect. the emc1023 uses an interlock mechanism that prevents changes in regist er content when fresh readings come in from the adc during successive reads from a host. when the high byte is read, the last conversion value is latched into the high byte and low byte. please note that the interlock mechanism is only effective when reading the high byte first. table 4.1 register table read address (hex) write address (hex) register name default value (hex) 00 n/a legacy format internal temperature high byte 00 23 n/a legacy format internal temperature low byte 00 01 n/a legacy format remote temperature 1 high byte 00 10 n/a legacy format remote temperature 1 low byte 00 f8 n/a legacy format remote temperature 2 high byte 00 f9 n/a legacy format remote temperature 2 low byte 00 fa n/a extended format remote temperature 1 high byte 00 fb n/a extended format remote temperature 1 low byte 00 fc n/a extended format remote temperature 2 high byte 00 fd n/a extended format remote temperature 2 low byte 00 02 n/a status register 00 03 09 configuration register 47 n/a 0f one shot command -- 27 27 remote 1 ideality factor 12 28 28 remote 2 ideality factor 12 ed n/a product id 04 (-1) 05 (-2) 06 (-3) 07 (-4) fe n/a manufacturer id 5d ff n/a revision number 01
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 12 smsc emc1023 datasheet 4.5 temperature monitor registers as shown in table 4.1 , each temperature monitor has two byte wide data registers. the external monitors are equipped with both legacy and ext ended data format. the 11 bit data temperature is stored aligned to the left resulting in the high byte to contain temperature in 1 c steps and the low byte to contain fractions of c as outlined below: 4.6 legacy temperature data fo rmat registers 00h, 23h, 01h, 10h, f8h, f9h: for registers displaying legacy temperature data fo rmat, the temperature range spans from ?63.875oc to +127.875oc with 0.125oc resolution. temperatures outside this range are clipped to ?63.875oc and +127.875oc. data is stored in the regist ers in 2?s complement as shown in ta b l e 4 . 4 : table 4.2 high byte temperature register register bit 7bit 6bit 5bit 4bit 3bit 2bit 1bit 0 temperature high byte registers 00h, 01h, f8h, fah, fch sign6432168421 table 4.3 low byte temperature register register bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 temperature low byte registers 23h, 10h, f9h, fbh, fdh 0.5000.2500.12500000 table 4.4 legacy temperature data format temperature ( c) 2?s complement hex diode fault 100 0000 0000 400 = -63.875 110 0000 0001 601 -63 110 0000 1000 608 -1 111 1111 1000 7f8 0 000 0000 0000 000 +0.125 000 0000 0001 001 +1 000 0000 1000 008 +127 011 1111 1000 3f8 +127.875 011 1111 1111 3ff
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 13 revision 1.2 (04-15-05) datasheet 4.7 extended temperature data format registers fah, fbh, fch, fdh for registers displaying extended temperature data format, a value of 64d is subtracted from the legacy format output. this effectively extends the range to cover higher external temperature measurements while still maintaining the 2?s comple ment format. obviously, the host will have to compensate and add 64d to the read temperatur e data. this format spans from ?63.875oc to +191.875oc with 0.125oc resolution. temperatures outside this range are limited to ?63.875oc and +191.875oc. table 4.5 shows example temperature readings and register content for this data format. table 4.4 and ta b l e 4 . 5 show that temperature data is stored in 2?s complement in both legacy and extended temperature data format. both extended and legacy temperature formats are updated simultaneously after every conversion cycle. code 400h is reserved for diode fault signaling which occurs when open or short conditions are pr esent between the external dp and dn pins. 4.8 status register the status register is a read only register and return s the operational status of the part. it indicates an external diode fault conditions through bit 0 and 1. when either d1 or d2 is set, a faulty diode connection is detected for external diode 1 or external diode 2 respectively. also, when diode faults are detected, temperature readings for the faulty external diode will return 400h. the emc1023 detects both open and short conditions for all diode pins. bit 7 of the status register will be set when the internal adc is busy converting data. table 4.5 extended temperature data format actual temp. ( c) -64 c offset ( c) 2?s complement of -64 c offset hex diode fault 100 0000 0000 400 = -63.875 -127.875 100 0000 0001 401 -63 -127 100 0000 1000 408 -1 -65 101 1111 1000 5f8 0 -64 110 0000 0000 600 +0.125 -63.875 110 0000 0001 601 +1 -63 110 0000 1000 608 +63 -1 111 1111 1000 7f8 +64 0 000 0000 0000 000 +65 1 000 0000 1000 008 +191 127 011 1111 1000 3f8 = +191.875 127.875 011 1111 1111 3ff table 4.6 status register register bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 def status busy - - - - - d2 d1 00h
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 14 smsc emc1023 datasheet 4.9 configuration register bits 0 through bit 2 of the config uration register set the adc c onversion rate of the part. see ta b l e 4 . 8 , ?configuration register, conversion rate,? on page 14 a conversion for all 3 temperature readings take s about 60ms. therefore, the maximum conversion rate, equals 16 conversions per second. bits 6 set of the configuration regist er sets the power mode of the part: in run mode, the emc1023 will operate at the preset conversion rate. in standby mode, the part is powered down to minimize current consumption. the smbus is fully operational in either mode. in standby mode, a write command to the one shot regi ster will trigger a one time conversion of the 3 temperature monitors. after the part finishes th e conversion, it will go back to standby mode. the host can now read the updated temperature information. table 4.7 configuration register register bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 def configuration - nrun/stop - - - cr2 cr1 cr0 47h table 4.8 configuration register, conversion rate cr2, cr1, cr0 conversion rate 000 reserved 001 reserved 010 reserved 011 1 conversions per second 100 2 conversions per second 101 4 conversions per second 110 8 conversions per second 111 16 conversions per second table 4.9 configuration registers data format nrun/stop description 0 run mode 1 standby mode
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 15 revision 1.2 (04-15-05) datasheet 4.10 ideality factor register the ideality factor registers are us ed to program the remote diode ideality factor into the emc1023 so that this error source can be eliminated. the default ideality factor is 1.008 and has a value of xx010010b or 12h. table 4.10 diode ideality factor values diode ideality factor value diode ideality factor value diode ideality factor value diode ideality factor value 0.9850 xx00 0000 1.0054 xx01 0000 1.0267 xx10 0000 1.0489 xx11 0000 0.9862 xx00 0001 1.0067 xx01 0001 1.0280 xx10 0001 1.0503 xx11 0001 0.9875 xx00 0010 1.0080 xx01 0010 1.0294 xx10 0010 1.0517 xx11 0010 0.9888 xx00 0011 1.0093 xx01 0011 1.0308 xx10 0011 1.0531 xx11 0011 0.9900 xx00 0100 1.0106 xx01 0100 1.0321 xx10 0100 1.0546 xx11 0100 0.9913 xx00 0101 1.0119 xx01 0101 1.0335 xx10 0101 1.0560 xx11 0101 0.9925 xx00 0110 1.0133 xx01 0110 1.0349 xx10 0110 1.0574 xx11 0110 0.9938 xx00 0111 1.0146 xx01 0111 1.0363 xx10 0111 1.0589 xx11 0111 0.9951 xx00 1000 1.0159 xx01 1000 1.0377 xx10 1000 1.0603 xx11 1000 0.9964 xx00 1001 1.0173 xx01 1001 1.0391 xx10 1001 1.0618 xx11 1001 0.9976 xx00 1010 1.0186 xx01 1010 1.0404 xx10 1010 1.0632 xx11 1010 0.9989 xx00 1011 1.0199 xx01 1011 1.0418 xx10 1011 1.0647 xx11 1011 1.0002 xx00 1100 1.0213 xx01 1100 1.0432 xx10 1100 1.0661 xx11 1100 1.0015 xx00 1101 1.0226 xx01 1101 1.0446 xx10 1101 1.0676 xx11 1101 1.0028 xx00 1110 1.0240 xx01 1110 1.0460 xx10 1110 1.0690 xx11 1110 1.0041 xx00 1111 1.0253 xx01 1111 1.0475 xx10 1111 1.0705 xx11 1111
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 16 smsc emc1023 datasheet chapter 5 application information this chapter provides information on maintaining accuracy when using diodes as remote sensors with smsc environmental monitoring and control devices. it is assumed that the users have some familiarity with hardware design and transistor characteristics. smsc supplies a family environmental monitoring and control (emc) devices that are capable of accurately measuring temperatures. most devices include an internal temperature sensor along with the ability to measure one or more external sensor s. the characteristics of an appropriate diode for use as the external sensor are listed in this chap ter. recommendations for the printed circuit board layout are provided to help reduce error caus ed by electrical noise or trace resistance. 5.1 maintaining accuracy 5.1.1 physical factors temperature measurement is performed by measuring the change in forward bias voltage of a diode when different currents are forced through the juncti on. the circuit board itself can impact the ability to accurately measure these small changes in voltage. 5.1.1.1 layout apply the following guidelines when designing the printed circuit board: 1. route the remote diode traces on the top layer. 2. place a ground guard signal on both sides of the differential pair. this guard band should be connected to the ground plane at least every 0.25 inches. 3. place a ground plane on the layer immediately below the diode traces. 4. keep the diode traces as short as possible. 5. keep the diode traces parallel, and the length of the two traces ident ical within 0.3 inches. 6. use a trace width of 0.01 inches with a 0.01 inch guard band on each side. 7. keep the diode traces away from sources of high frequency noise such as power supply filtering or high speed digital signals. 8. when the diode traces must cross high speed di gital signals, make them cross at a 90 degree angle. 9. avoid joints of copper to solder that can introduce thermocouple effects. these recommendations are illustrated in figure 5.1 routing the diode traceson page 16 . figure 5.1 routing the diode traces copper trace copper trace .01 wide min. .01 gap min. .01 wide min. gnd plane .01 gap min. gnd plane .01 gap min. copper plane (to shield from noise) board material recommend via stictching at .25 inch intervals. dp or dn dp or dn
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 17 revision 1.2 (04-15-05) datasheet 5.1.1.2 bypass capacitors accurate temperature measurements require a clean, stable power supply. locate a 0.1f capacitor as close as possible to the power pin with a good ground. a low esr capacitor (such as a 10f ceramic) should be placed across the power source. add additional power supply filtering in systems that have a noisy power supply. a capacitor may be placed across th e dp/dn pair at the remote sensor in noisy environments. do not exceed a value of 2.2nf if this capacitor is installed. 5.1.1.3 manufacturing circuit board assembly processes may leave a residue on the board. this residue can result in unexpected leakage currents that may introduce errors if the circuit board is not clean. for example, processes that use water-soluble soldering fluxes have been known to cause problems if the board is not kept clean. 5.1.1.4 thermal considerations keep the sensor in good thermal contact with the co mponent to be measured. the temperature of the leads of a discrete diode will greatly impact the temperatur e of the diode junction. make use of the printed circuit board to disperse any self-heating that may occur. 5.1.1.5 remote sensors connected by cables when connecting remote diodes with a cable (instead of traces on the pcb) use shielded twisted pair cable. the shield should be attached to ground near the emc1023, and should be left unconnected at the sensor end. belden 8451 cable is a good choice for this application. 5.1.2 sensor characteristics the characteristics of the diode junction used for temperature sensing will affect the accuracy of the measurement. 5.1.2.1 selecting a sensor a diode connected small signal transistor is reco mmended. silicon diodes are not a good choice for remote sensors. small signal transistors such as the 2n3904 or the 2n3906 are recommended. select a transistor with a co nstant value of h fe in the range of 2.5 to 220 microamps. the magnitude of h fe is not critical, and the variation in h fe from one device to another canc els out of the temperature equations. 5.1.2.2 compensating for ideality of the diode the remote diode may have an ideality factor based on the manufacturing proce ss. inaccuracy in the temperature measurement resulting from this ideality factor may be eliminated by configuring the ideality factor register. the emc1023 is trimmed to an ideality factor of 1.008. 5.1.2.3 circuit connections the more negative terminal for the remote temperatur e diode, dn, is internal ly biased with a forward diode voltage. terminal dn is not referenced to ground. remote temperature diodes can be constructed as shown in figure 5.2 remote temperature diode exampleson page 18 .
1c triple temperature sensor with resistance error correction datasheet revision 1.2 (04-15-05) 18 smsc emc1023 datasheet figure 5.2 remote temperature diode examples environmental monitoring and control (emc) dev ices supplied by smsc are designed to make accurate temperature measurements. careful design of the printed circuit board and proper selection of the remote sensing diode will help to maintain the accuracy. to dp to dn local ground typical remote parasitic substrate transistor e.g. cpu substrate pnp to dp to dn to dp to dn typical remote discrete pnp transistor e.g 2n3906 typical remote discrete npn transistor e.g. 2n3904
1c triple temperature sensor with resistance error correction datasheet smsc emc1023 19 revision 1.2 (04-15-05) datasheet chapter 6 package outline figure 6.1 8-pin msop package ou tline - 3x3mm body 0.65mm pitch table 6.1 8-pin msop package parameters notes: 1. controlling unit: millimeters. 2. tolerance on the true position of the leads is 0.065 mm maximum. 3. package body dimensions d and e1 do not includ e mold protrusion or flash. dimensions d and e1 to be determined at datum plane h. maximum mo ld protrusion or flash is 0.15mm (0.006 inches) per end, and 0.15mm (0.006 inches) per side. 4. dimension for foot length l measured at the gauge plane 0.25 mm ab ove the seating plane. 5. details of pin 1 identifier are optional but must be located within the zone indicated. min nominal max remarks a 0.80 ~ 1.10 overall package height a1 0.05 ~ 0.15 standoff a2 0.75 0.85 0.95 body thickness d 2.80 3.00 3.20 x body size e 4.65 4.90 5.15 y span e1 2.80 ~ 3.20 y body size h 0.08 ~ 0.23 lead foot thickness l 0.40 ~ 0.80 lead foot length l1 0.95 ref lead length e 0.65 bsc lead pitch 0 o ~8 o lead foot angle w 0.22 ~ 0.38 lead width ccc ~ ~ 0.10 coplanarity

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