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this is preliminary information on a new product now in dev elopment or undergoing evaluati on. details are subject to change without notice. march 2013 docid024394 rev 1 1/19 19 STEF05D electronic fuse for 5 v line datasheet - preliminary data features ? continuous current typ: 3.6 a ? n-channel on-resistance typ: 40 m ? ? enable/fault functions ? output clamp voltage typ: 6.65 v ? undervoltage lockout ? short-circuit limit ? overload current limit ? controlled output voltage ramp ? thermal latch typ: 165 c ? uses tiny capacitors ? operating junction temp. - 40 c to 125 c ? available in dfn10 (3 x 3 mm). applications ? hard disk drives ? solid state drives (ssd) ? hard disk and ssd arrays ? set-top boxes ? dvd and blu-ray disc drivers description the STEF05D is an integrated electronic fuse optimized for monitoring output current and input voltage. connected in series to a 5 v rail, it is capable of protecting the electronic circuitry on its output from overcurrent and overvoltage. the device has a controlled delay and turn-on time. when an overload condition occurs, the STEF05D limits the output current to a predefined safe value. if the anomalous overload condition. persists, it goes into an open state, disconnecting the load from the power supply. if a continuous short-circuit is present on the board, when power is re-applied the e-fuse in itially limits the output current to a safe value, and then again goes into an open state. the device is equipped with a thermal protection circuit. the intervention of the thermal protection is signal led to the board monitoring circuits through a signal on the fault pin. unlike mechanical fuses, which must be physically replaced after a single event, the e- fuse does not degrade in its performance after short-circuit/thermal protection interventions and it is reset either by recycling the supply voltage or using the enable pin. the companion chip for 12 v power rails is also available with part number stef12. dfn10 (3 x 3 mm) table 1. device summary order code package packaging STEF05Dpur dfn10 (3 x 3 mm) tape and reel www.st.com
contents STEF05D 2/19 docid024394 rev 1 contents 1 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1.1 turn-on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1.2 normal operating condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.3 output voltage clamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.4 current limiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.5 thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.2 r limit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.3 c dv/dt calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.4 enable/fault pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6 typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
docid024394 rev 1 3/19 STEF05D block diagram 1 block diagram figure 1. device block diagram am09891v1
pin configuration STEF05D 4/19 docid024394 rev 1 2 pin configuration figure 2. pin configuration (top view) table 2. pin description pin n symbol note 1 to 5 v out/ source connected to the source of the intern al power mosfet and to the output terminal of the fuse 6 nc not connected 7 i-limit a resistor between this pin and the source pin sets the overload and short- circuit current limit levels. 8 en/fault the enable/fault pin is a tri-state, bi-directional interface. during normal operation the pin must be left floating, or it can be used to disable the output of the device by pulling it to ground using an open drain or open collector device. if a thermal fault occurs, the voltage on this pin will go to an intermediate state to signal a monitor circuit that th e device is in thermal shutdown. it can be connected to another device of th is family to cause a simultaneous shutdown during thermal events. 9dv/dt the internal dv/dt circuit controls the slew rate of the output voltage at turn- on. the internal capacitor allows a ramp-up time of around 1ms. an external capacitor can be added to this pin to increase the ramp time. if an additional capacitor is not required, this pin should be left open. 10 gnd ground pin 11 v cc exposed pad. positive input vo ltage must be connected to v cc . v cc source source source source source gnd dv/dt en/fault i-limit n/c am09867v1
docid024394 rev 1 5/19 STEF05D maximum ratings 3 maximum ratings note: absolute maximum ratings ar e those values beyond which damage to the device may occur. functional operation under these conditions is not implied. table 3. absolute maximum ratings symbol parame ter value unit v cc positive power supply voltage (steady state) -0.3 to 10 v positive power supply voltage (max 100 ms) -0.3 to 15 v out /source (max 100 ms) -0.3 to vcc+0.3 v i-limit (max 100 ms) -0.3 to 15 v en/fault -0.3 to 7 v dv/dt -0.3 to 7 v t op operating junction temperature range (1) 1. the thermal limit is set above the maximum thermal rating. it is not recommended to operate the device at temperatures greater than the maximu m ratings for extended periods of time. -40 to 125 c t stg storage temperature range -65 to 150 c t lead lead temperature (soldering) 10 sec 260 c table 4. thermal data symbol parameter value unit r thja thermal resistance junction-ambient 52.7 c/w r thjc thermal resistance junction-case 17.4 c/w table 5. esd performances symbol parameter test conditions value unit esd esd protection hbm 2 kv mm 150 v cdm 500 v
electrical characteristics STEF05D 6/19 docid024394 rev 1 4 electrical characteristics v cc = 5 v, v en = 3.3 v, c i = 10 f, c o = 47 f, t j = 25 c, unless otherwise specified table 6. electrical characteristics for STEF05D symbol parameter test conditions min. typ. max. unit under/overvoltage protection v clamp output clamping voltage v cc = 10 v 5.95 6.65 7.7 v v uvlo undervoltage lockout turn-on, voltage going up 3.2 3.6 4.3 v v hyst uvlo hysteresis 0.40 v power mosfet t dly delay time enabling of chip to i d = 100 ma with a 1 a resistive load 200 s r dson on resistance (1) t j = 25 c 40 60 m ? t j = 125 c (2) 70 v off off state output voltage v cc = 10 v, v gs = 0, r limit = infinite 50 200 mv i d continuous current 0.5 inch2 pad (2) , t a = 25 c 3.6 a minimum copper, t a = 80 c 1.7 current limit i short short-circuit current limit r limit = 11 ? 3.1 4.1 5.1 a i lim overload current limit r limit = 11 ? 4a dv/dt circuit dv/dt output voltage ra mp time enable to v out =4.7v, no c dv/dt 0.8 ms enable/fault v il low level input voltage (2) output disabled 0.35 0.58 0.81 v v i(int) intermediate level input voltage (2) thermal fault, output disabled 0.82 1.4 1.95 v v ih high level input voltage ou tput enabled 1.96 2.64 3.3 v v i(max) high state maximum voltage 3.4 4.3 5.4 v i il low level input current (sink) v enable = 0 v -10 -30 a i i high level leakage current for external switch v enable = 3.3 v 1 a maximum fan-out for fault signal total numbers of chips that can be connected to this pin for simultaneous shutdown 3units
docid024394 rev 1 7/19 STEF05D electrical characteristics total device i bias bias current device operational 0.5 2 ma thermal shutdown 1 v min minimum operating voltage 3.1 v thermal latch tsd shutdown temperature (2) 165 c 1. pulse test: pulse width = 300 s, duty cycle = 2% 2. limits in temperature are guaranteed by design, but not tested in production table 6. electrical characteristics for STEF05D symbol parameter test conditions min. typ. max. unit
typical application STEF05D 8/19 docid024394 rev 1 5 typical application 5.1 operating modes 5.1.1 turn-on when the input voltage is applied, the enable/fault pin goes up to the high state, enabling the internal control circuitry. after an initial delay time of typically 200 s, the output voltage is supplied with a slope defined by the internal dv/dt circuitry. if no a dditional capacitor is conne cted to dv/dt pin, the total time from the enable signal going high and the output voltage reaching the nominal value is around 1 ms (refer to figure 5 and figure 7 ). figure 3. application circuit figure 4. typical hdd application circuit am09868v1 am09869v1
docid024394 rev 1 9/19 STEF05D typical application 5.1.2 normal operating condition the STEF05D e-fuse behaves like a mechanical fuse, buffering the circuitry on its output with the same voltage shown at its input, wit h a small voltage fall due to the n-channel mosfet r dson . 5.1.3 output voltage clamp this internal protection circuit clamps the outp ut voltage to a maximum safe value, typically 6.65v, if the input voltage exceeds this threshold. 5.1.4 current limiting when an overload event occurs, the current limit ing circuit reduces the conductivity of the power mosfet, in order to clamp the output current at the value selected externally by means of the limiting resistor r limit ( figure 3 ). 5.1.5 thermal shutdown if the device temperature exceeds the thermal latch threshold, typically 165c, the thermal shutdown circuitry turns the power mosfet off, thus disconnecting the load. the en/fault pin of the device will automatically be set at an interme diate voltage, in or der to signal the overtemperature event. from this condition the e-fuse can be reset eith er by cycling the supply voltage or by pulling down the en pin below the v il threshold, and then releasing it. 5.2 r limit calculation as shown in figure 3 , the device uses an internal n-channel sense fet with a fixed ratio, to monitor the output current and limit it at the level set by the user. the r limit value for achieving the requested current limitation can be estimated by using the following theoretical formula, together with the graph in figure 13 : equation 1 5.3 c dv/dt calculation connecting a capacitor between the c dv/dt pin and gnd will allow the modification of the output voltage ramp time. given the desired time interval ? t during which the output voltage goes from zero to his maximum value, the capacitance to be added on c dv/dt pin can be calculated using the following theoretical formula: r limit 42 ishort ---------------- =
typical application STEF05D 10/19 docid024394 rev 1 equation 2 where c dv/dt is expressed in farad, and the time ? t in seconds. figure 5 shows a graphical explanation of delay time and ramp-up time. figure 5. delay time and v out ramp-up time 5.4 enable/fault pin the enable/fault pin has the dual function of contro lling the output of th e device and, at the same time, of providing information about the device status to the application. when it is used, it should be connected to an external open-drain or open-collector device. in this case, when it is pulled at low logic level, it turns the output of the e-fuse off. if this pin is left floating, since it has internal pu ll-up circuitry, the output of the e-fuse is kept on in normal operating conditions. in case of thermal fault, the pin is pulled to an intermediate state ( figure 6 ). this signal can be provided to a monitor circuit, informing it t hat a thermal shutdown has occurred, or it can be directly connected to the enable/fault pins of other stefxx devices on the same application in order to achieve a simultaneous enable/disable feature. when a thermal fault occurs, the device can be reset either by cycling the supply voltage or by pulling down the en able pin below the v il threshold and then releasing it. c dvdt 36 10 9 ? ?? t30x10 12 ? ? = am09870v1 0 1 2 3 4 5 6 v time en/fault vout delay time ramp-up time
docid024394 rev 1 11/19 STEF05D typical application figure 6. enable/fault pin status am09871v1 0 1 2 3 4 5 en/fault voltage [v] time normal operating condition thermal fault condition off/reset
typical performance characteristics STEF05D 12/19 docid024394 rev 1 6 typical performance characteristics the following plots are referred to the typical application circuit and, unless otherwise noted, at t a = 25c. figure 7. v out ramp-up vs. en/fault figure 8. startup vs. v cc figure 9. startup @ short-circuit figure 10. startup @ heavy load figure 11. startup vs. en/fault figure 12. clamp voltage vcc vout en/flt vcc vout en/flt vout vcc en/flt iin vout iin en/flt vcc en/flt vcc vout vcc vout
docid024394 rev 1 13/19 STEF05D typical performance characteristics figure 13. current limit vs. r limit figure 14. r dson vs. temperature i lim i short r limit am09877v2 20 30 40 50 60 70 80 -40 -25 0 25 55 85 125 150 r ds on (m ) temperature ( c) v cc = 5 v
package mechanical data STEF05D 14/19 docid024394 rev 1 7 package mechanical data in order to meet environmental requirements, st offers these devices in different grades of ecopack ? packages, depending on their level of environmental compliance. ecopack ? specifications, grade definitions a nd product status are available at: www.st.com . ecopack ? is an st trademark. table 7. dfn10l (3 x 3 mm.) mechanical data dim. mm. min. typ. max. a 0.80 0.90 1.00 a1 0.02 0.05 a2 0.55 0.65 0.80 a3 0.20 b 0.18 0.25 0.30 d 2.85 3.00 3.15 d2 2.20 2.70 e 2.85 3.00 3.15 e2 1.40 1.75 e3 0.230 e4 0.365 e0.50 l 0.30 0.40 0.50 ddd 0.08
docid024394 rev 1 15/19 STEF05D package mechanical data figure 15. dfn10l package outline 7426335_h
package mechanical data STEF05D 16/19 docid024394 rev 1 dim. mm. inch. min. typ. max. min. typ. max. a 330 12.992 c 12.8 13.2 0.504 0.519 d 20.2 0.795 n 60 2.362 t18.40.724 ao 3.3 0.130 bo 3.3 0.130 ko 1.1 0.043 po 4 0.157 p8 0.315 tape and reel qfnxx/dfnxx (3x3 mm) mechanical data
docid024394 rev 1 17/19 STEF05D package mechanical data figure 16. dfn10l footprint - recommended data (dimensions in mm.) 7426335_h
revision history STEF05D 18/19 docid024394 rev 1 8 revision history table 8. document revision history date revision changes 19-mar-2013 1 initial release.
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