RT9726 1 ds9726-01 april 2011 www.richtek.com pin configurations (top view) sc-70-6 general description the RT9726 is a temperature switch with wide input voltage range. the over-temperature threshold point is generated by a negative temperature coefficient (ntc) thermistor and a setting resistor. the RT9726 provides an active-low, open- drain logic output. ot goes low when the ntc pin voltage is lower than 50% of the ref voltage threshold. the RT9726 provides the selectable hysteresis mode that can be set by the en pin input voltage. the ic is available in sc-70-6 package. typical application circuit marking information ordering information note : richtek products are : ` rohs compliant and compatible with the current require- ments of ipc/jedec j-std-020. ` suitable for use in snpb or pb-free soldering processes. features z z z z z wide input voltage range : 4.75v to 25v z z z z z 0.5 a shutdown current z z z z z 2 selectable hysteresis threshold z z z z z reference output for thermal threshold setting z z z z z open-drain logic output z z z z z rohs compliant and halogen free applications z notebook temperature monitoring z microprocessor thermal management z temperature control z fan control z electronic system protection en ref vin gnd ntc 4 23 5 6 ot high-voltage hysteresis selectable temperature switch en RT9726 vin 4.75v to 25v gnd 23 6 1 ref ntc c1 0.1f chip enable 3.3v ot 5v system shdn# r1 570 thermistor ? = 4250 10k system shutdown switch @ temp = 100c for default hysteresis 30c 4 5 100k v in a1=w a1= : product code w : date code RT9726 package type u6 : sc-70-6 lead plating system g : green (halogen free and pb free)
RT9726 2 ds9726-01 april 2011 www.richtek.com function block diagram pin no. pin name pin function 1 vin high voltage power supply input. this pin should be bypassed with a 0.1 f capacitor to ground. 2 gnd ground pin. tie the ground pin close to temperature sensing thermistor. 3 ntc this pin should connect a thermistor resistor to ground. the ntc pin will sense the external thermistor cross voltage and provide typical 50%ref over-temperature threshold for ot pin. 4 ot open-drain and active-low output. ot will go low when ntc pin is lower than typical 50%ref over-temperature threshold. 5 ref reference output. this pin should connect with a resistor to ntc pin to set the over- temperature threshold. 6 en chip enable (active high). this pin can be used for the over-temperature threshold hysteresis setting. functional pin description ref hysteresis control + - en ref vin gnd ntc ot
RT9726 3 ds9726-01 april 2011 www.richtek.com electrical characteristics (no load on ref, v in = 7v, v en = 5v, t a = 25 c, unless otherwise specified) parameter symbol test conditions min typ max unit input supply vin shutdown current i vin v in = 4.75v to 25v, en = gnd -- -- 3 a vin quiescent current i q v in = 4.75v to 25v, en = 5v, no load on ref -- 100 150 a ref output ref output voltage ref no external load 1.978 2 2.022 v ref output current i ref in 1% ref drop -- -- 2 ma logic output ot output low voltage ot sink current = 4ma -- -- 0.2 v temperature threshold configure over-temperature threshold ntc/ref ot = high 47.5 50 52.5 % mode = hyst1, ot = low 62.5 65 67.5 % over-temperature recovery threshold ntc/ref mode = hyst2, ot = low 70 72.5 75 % shutdown -- -- 0.4 v set hyst1 mode 1.2 -- 2.4 v en input voltage en set hyst2 mode 2.9 -- -- v absolute maximum ratings (note 1) z vin to gnd ------------------------------------------------------------------------------------------------------------------ ? 0.3v to 28v z ntc, ot, ref, en to gnd ---------------------------------------------------------------------------------------------- ? 0.3v to 6v z power dissipation, p d @ t a = 25 c sc-70-6 ---------------------------------------------------------------------------------------------------------------------- 0.3w z package thermal resistance (note 2) sc-70-6, ja ---------------------------------------------------------------------------------------------------------------- 333 c/w z lead temperature (soldering, 10 sec.) ------------------------------------------------------------------------------- 260 c z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z storage temperature range -------------------------------------------------------------------------------------------- ? 65 c to 150 c z esd susceptibility (note 3) hbm (human body mode) ---------------------------------------------------------------------------------------------- 2kv mm (ma chine mode) ------------------------------------------------------------------------------------------------------ 200v recommended operating conditions (note 4) z supply input voltage, v in ------------------------------------------------------------------------------------------------ 4.75v to 25v z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c
RT9726 4 ds9726-01 april 2011 www.richtek.com note 1. stresses listed as the above " absolute maximum ratings " may cause permanent damage to the device. these are for stress ratings. functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. note 2. ja is measured in the natural convection at t a = 25 c on a low effective single layer thermal conductivity test board of jedec 51-3 thermal measurement standard. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions.
RT9726 5 ds9726-01 april 2011 www.richtek.com typical operating characteristics over temperature recovery threshold time (1ms/div) v en (5v/div) ot (5v/div) v ref (5v/div) v ntc (1v/div) v en = 3.3v, v in = ot = 5v, c in = 0.1 f over temperature recovery threshold time (1ms/div) v en (2v/div) ot (5v/div) v ref (5v/div) v ntc (1v/div) v en = 1.8v, v in = ot = 5v, c in = 0.1 f start up from en time (5ms/div) v en (5v/div) ot (5v/div) v ref (2v/div) v ntc (1v/div) v in = ot = 5v, c in = 0.1 f shutdown current vs. input voltage 0.40 0.45 0.50 0.55 0.60 5 7 9 11 13 15 17 19 21 23 25 input voltage (v) shutdown current (ua) v en = 0v, no load quiescent current vs. input voltage 100 101 102 103 104 105 5 7 9 1113151719212325 input voltage (v) quiescent current (ua) v en = 5v, no load
RT9726 6 ds9726-01 april 2011 www.richtek.com application information the RT9726 is a temperature switch with wide input voltage range from 4.75v to 25v. it provides an accurate reference output voltage. by adding a negative temperature coefficient (ntc) thermistor from ntc pin to gnd and a resistor from ref to ntc pin, a temperature-dependent voltage can be achieved. when the ntc pin voltage is lower than 50% of the ref voltage threshold, the ot pin goes low. the RT9726 provides a selectable hysteresis mode that can be set by controlling the en pin voltage. over temperature threshold setting the ot pin state is an open-drain logic output. as shown in table 1, the ot pin will go low and shut down the RT9726 when v ntc 50% of v ref . when v ntc > 50% of v ref, the ot pin will be pulled high by the external resistor. table 1. ntc over temperature threshold ntc pin voltage ot pin state > 50% v ref pulled high 50% v ref low over temperature recovery threshold the RT9726 supports two temperature recovery thresholds as shown in the table 2. it is set by en pin voltage. for example, set en pin voltage at 3.3v then ot pin will be released if v ntc rises to above 70% of the v ref . recovery mode en input voltage ntc pin recovery threshold voltage (min.) recovery temperature threshold (1) hyst 1 v en = 1.2v to 2.4v 62.5% v ref ? 20c hyst 2 v en = 2.9v to 5.5v 70% v ref ? 30c table 2. recovery mode and ntc recovery threshold voltage por and shutdown power-on reset (por) occurs when input voltage rises above 3.9v (typical), the ot pin will be released when v ntc is higher then 50% v ref . by setting the en pin voltage below 0.4v, the ref pin voltage goes low and then the RT9726 will be shut down. design example figure 1. shows the typical fan control application circuit. when the ntc pin voltage is lower than 50% of v ref , the ot will go low to turn on the fan. note 1 : thermistor = 4250 and temperature threshold is set at 100 c. figure 1. fan control application ?? ? ?? ?? d d 11 t1 t2 t1 t2 t1 t2 r = r e r : the resistance of ntc thermistor at t1 ( k) r : the resistance of ntc thermistor at t2 ( k) : the coefficient of ntc thermistor if the thermal shut-down threshold is set at 75 c and r t2 = 10k (under 25 c) with = 4250, r1 can be calculated by using the equation as follows : ?? ? ?? ++ ?? d 11 4250 273.15 75 273.15 25 (t1 = 75 c) r1 = r = 10k e = 1.29k en RT9726 vin 4.75v to 25v gnd 2 3 6 1 ref ntc c1 0.1f 1.8v ot 5v r1 1.29k thermistor ? = 4250 10k 4 5 100k r hyst fan control switch @ temp = 75c for hysteresis 20c v in chip enable
RT9726 7 ds9726-01 april 2011 www.richtek.com thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundings airflow and temperature difference between junction to ambient. the maximum power dissipation can be calculated by following formula : p d(max) = (t j(max) ? t a ) / ja where t j(max) is the maximum operation junction temperature, t a is the ambient temperature and the ja is the junction to ambient thermal resistance. for recommended operating conditions specification of the RT9726, the maximum junction temperature is 125 c and t a is the maximum ambient temperature. the junction to ambient thermal resistance ja is layout dependent. for sc-70-6 packages, the thermal resistance ja is 333 c /w on the standard jedec 51-3 single layer thermal test board. the maximum power dissipation at t a = 25 c can be calculated by following formula : p d(max) = (125 c ? 25 c) / (333 c / w) = 0.3w for sc-70-6 package the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance ja . for RT9726 package, the figure 2 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. figure 2. derating curves for RT9726 package 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0 25 50 75 100 125 ambient temperature (c) maximum power dissipation (w) sc-70-6 single layer pcb layout considerations for best performance of the RT9726, the input capacitor should be placed as close to the vin pin and ground plane as possible to reduce noise coupling. en ref vin gnd ntc 4 2 3 5 6 ot c in the input capacitor should be placed as close as possible to the ic. figure 3. pcb layout guide
RT9726 8 ds9726-01 april 2011 www.richtek.com richtek technology corporation headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 information that is provided by richtek technology corporation is believed to be accurate and reliable. richtek reserves the ri ght to make any change in circuit design, specification or other related things if necessary without notice at any time. no third party intellectual property inf ringement of the applications should be guaranteed by users when integrating richtek products into any application. no legal responsibility for any said applications i s assumed by richtek. richtek technology corporation taipei office (marketing) 5f, no. 95, minchiuan road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)86672399 fax: (8862)86672377 email: marketing@richtek.com a a1 e b b d c h l sc-70-6 surface mount package dimensions in millimeters dimensions in inches symbol min max min max a 0.800 1.100 0.031 0.044 a1 0.000 0.100 0.000 0.004 b 1.150 1.350 0.045 0.054 b 0.150 0.400 0.006 0.016 c 1.800 2.450 0.071 0.096 d 1.800 2.250 0.071 0.089 e 0.650 0.026 h 0.080 0.260 0.003 0.010 l 0.210 0.460 0.008 0.018 outline dimension
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