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fpf2310/12/13/13l ? dual-output adjustable current limit switch may 2010 ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 fpf2310/12/13/13l dual-output adjustable current limit switch features ? 1.8 to 5.5v input voltage range ? typical r on = 75m ? at in = 5.5v ? 400~600ma adjustable current limit ? 10% current limit accuracy from typical ? slew rate controlled ? esd protected, above 4000v hbm ? independent thermal shutdown ? uvlo ? output discharge ? rohs compliant applications ? smart phones ? enterprise equipment ? peripheral usb ports and accessories related resources fpf2310/12/13/13l evaluation board user guide; power switch for usb applications description the fpf2310/12/13/13l are dual-channel load switches of the intellimax? family. the fpf2310/12/13/13l consist of dual, independent, current-limited, and slew rate controlled, p-channel mosfet power switches. slew rated turn-on prevents inrush current from glitching supply rails. the input voltage range operates from 1.8v to 5.5v to fulfill usb device supply requirements. switch control is accomplished by a logic input (on) capable of interfacing directly with low-voltage control signals. for the fpf2312, if the constant-current condition persists after 10ms, the part shuts down the switch. the fpf2310 has an auto-restart feature that turns the switch on again after 150ms if the on pin is still active. fpf2313/13l remains in constant-current mode until the switch current falls below the current limit. for fpf2310 through fpf2313/13l, the minimum current limit is 400ma-600ma with 10% accuracy (+25c) for each switch to comply with usb applications in portable devices. fpf2310m/12/13/13l series is available in a space- saving, 8-lead, 3x3mm mlp . figure 1. 8-lead mlp (3x3mm) ordering information part number minimum current limit current limit blanking time auto restart on pin activity mode package FPF2310MPX 400-600ma 10ms 150ms active high restart 8-lead molded leadless package fpf2312mpx 400-600ma 10ms n/a active high latch off 8-lead molded leadless package fpf2313mpx 400-600ma 0ms n/a active high constant current 8-lead molded leadless package fpf2313lmpx 400-600ma 0ms n/a active low constant current 8-lead molded leadless package
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 2 application circuit figure 2. typical application functional block diagram figure 3. block diagram off on ona in gnd fpf2310/12/13/13l* isetb outa to load a iseta off on onb outb to load b c in c outb c outa in = 1.8v-5.5v *fpf2313l is active low in ona onb outa iseta outb isetb gnd current limit b output discharge thermal protection b current limit a output discharge thermal protection a control logic a uvlo control logic b
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 3 pin configuration figure 4. 8-lead mlp 3x3mm (bottom view) pin description pin name function 1 gnd ground 2 in supply input: input to the power switch and the supply voltage for the ic. 3 ona on / off control input of power switch a. 4 onb on / off control input of power switch b. 5isetb current limit set input for power switch b: a resist or from iset to ground sets the current limit for the switch. 6 outb switch output: output of the power switch b. 7 outa switch output: output of the power switch a. 8 iseta current limit set input for power switch a: a resist or from iset to ground sets the current limit for the switch. 9 thermal pad ic substrate, which can be connected to gnd fo r better thermal performance. do not connect to other pins. gnd in ona outb iseta mlp 3x3 8l bottom view 8 7 63 2 1 outa isetb 5 onb 4 9
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 4 absolute maximum ratings stresses exceeding the absolute maximum ratings may damage the device. the device may not function or be opera- ble above the recommended operating conditions and stressing the parts to these levels is not recommended. in addi- tion, extended exposure to stresses above the recommended operating conditions may affect device reliability. the absolute maximum ratings are stress ratings only . notes: 1. soldered thermal pad on a two-layer pcb without vias based on jedec std 51-3. 2. soldered thermal pad on a four-layer pcb without vias connected with gnd plane based on jedec std51-5, 7. recommended operating range the recommended operating conditions table defines the conditions for actual device operation. recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. fairchild does not recommend exceeding them or designing to absolute maximum ratings. symbol parameter min. max. unit in, outa, outb, on to gnd -0.3 6.0 v p d power dissipation 0.6 (1.) w 2.2 (2.) t stg storage temperature -65 +150 c ja thermal resistance, junction-to-ambient 216 (1.) c/w 57 (2.) esd electrostatic discharge protection human body model, jesd22-a114 4000 v charged device model, jesd22-c101 2000 v symbol parameter min. max. unit in supply input 1.8 5.5 v t a ambient operating temperature -40 +85 c
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 5 electrical characteristics in = 1.8 to 5.5v, t a = -40 to +85c unless otherwise noted. typical values are at in = 3.3v and t a = 25c. figure 5. timing diagram symbol parameter conditions min. typ. max. units basic operation v in operating voltage 1.8 5.5 v i q quiescent current in = 5.5v, i out = 0ma, v on = 5.5v (fpf2310/2/3), v on = 0v (fpf2313l) 52.5 94.5 a i sd in shutdown current in = 5.5v, outa = outb = short to gnd, v on = 0v (fpf2310/2/3), v on = 5.5v (fpf2313l) 1 a r on on resistance in = 5.5v, i out = 200ma, t a = 25c 75 140 m ? in = 5.5v, i out = 200ma, t a = -40c to +85c 90 r pd output pull-down resistance in = 3.3v, t a = 25c v on = 0v (fpf2310/2/3), v on = 3.3v(fpf2313l) 70 ? v ih on input logic high voltage (on) in = 1.8v 0.8 v in = 5.5v 1.4 v il on input logic low voltage in = 1.8v 0.5 v in = 5.5v 0.9 i on on input leakage v on = in or gnd -1 1 a protections i lim current limit in = 3.3v, outa = outb = 3v, r set = 690 ? , t a = 25c 450 500 550 ma tsd thermal shutdown shutdown threshold 140 c return from shutdown 130 hysteresis 10 v uvlo under-voltage shutdown in increasing 1.55 1.65 1.75 v v uvlo_hys under-voltage shutdown hysteresis 50 mv dynamic t on turn-on time r l = 500 ? , c l = 0.1 f111 s t off turn-off time r l = 500 ? 5 s t r outa, outb rise time r l = 500 ? , c l = 0.1 f13 s t f outa, outb fall time r l = 500 ? 2 s t blank over-current blanking time fpf2310, fpf2312 5 10 20 ms t rstrt auto-restart time fpf2310 75 150 300 ms t clr current limit response time in = 3.3v, moderate over-current condition 20 s 90% 10% 90% 10% 50% 50% 10% 90% t r t don t doff out t f out on t on = t r + t don t off = t f + t doff
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 6 typical characteristics 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 1.82.22.52.93.33.74.04.44.85.15.5 supply voltage (v) supply current (ua) ona = onb = in r set = 698 ohms 25c 8 5 c -40c 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 -40 -15 10 35 60 85 t j , junction temperature (c) i q current (ua) in = 3.3v in = 5.5v in = 1.8v ona = onb = in r set = 698 ohms 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -40 -15 10 35 60 85 t j , junction temperature (c) in shutdown current (ua) in = 5.5v on = out = 0v r set = 698 ohms 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -40 -15 10 35 60 85 t j , junction temperature (c) in shutdown current (ua) in = 5.5v on = out = 0v r set = 698 ohms 50 60 70 80 90 100 110 -40 -15 10 35 60 85 t j , junction temperature (c) on resistance (mohm) r on a r on b in = 5.5v ona = onb = 5.5v r set = 698 ohms i out = 200ma t a = 25c 60 65 70 75 80 85 1.82.22.52.93.33.74.04.44.85.15.5 supply voltage (v) pull-down resistance (ohm) r pd a r pd b ona = onb = 0v r set = 698 ohms i out = 1ma t a = 25c figure 9. r on vs. supply voltage figure 10. r on vs. temperature figure 11. r pd vs. supply voltage figure 8. in shutdown current vs. temperature figure 6. quiescent current vs. supply voltage figure 7. quiescent current vs. temperature
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 7 typical characteristics 50 55 60 65 70 75 80 -40 -15 10 35 60 85 t j , junction temperature (c) pull-down resistance (ohm) r pd a r pd b in = 5.5v ona = onb = 0v r set = 698 ohms i out = 1ma 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.82.22.52.93.33.74.04.44.85.15.5 supply voltage (v) on threshold voltage (v) v ih v il r set = 698 ohms t a = 25c 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -40 -15 10 35 60 85 t j , junction temperature (c) on threshold voltage (v) in = 3.3v in = 5.5v in = 1.8v r set = 698 ohms 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -40 -15 10 35 60 85 t j , junction temperature (c) on threshold voltage (v) in = 3.3v in = 5.5v in = 1.8v r set = 698 ohms 480 485 490 495 500 1.8 2.2 2.5 2.9 3.3 3.7 4.0 4.4 4.8 5.1 5.5 supply voltage (v) current limit (ma) ilim(typ)b r set = 698 ohms t a = 25c ilim(typ) a 480 482 484 486 488 490 492 494 496 498 500 -40 -15 10 35 60 85 t j , junction temperature (c) current limit (ma) in = 3.3v outa = outb = 3v ona = onb = 3.3v r set = 698 ohms ilim(typ)b ilim(typ) a figure 15. on low voltage vs. temperature figure 16. current limit vs. supply voltage figure 17. current limit vs. temperature figure 14. on high voltage vs. temperature figure 12. r pd vs. temperature figure 13. on threshold voltage vs. supply voltage
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 8 typical characteristics out 5v/div in = 5v on = 3.3v c out = 0.1 f r l = 500 ? r set = 680 ? on 2v/div in 5v/div 200 s/div out 5v/div in = 5v on = 3.3v c in = 10 f c out = 0.1 f r l = 500 ? r set = 680 ? on 2v/div in 5v/div 200 s/div i out 50ma/div 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 -40 -15 10 35 60 85 t j , junction temperature (c) blanking time (ms) outa outb fpf2310/12 in = 3.3v ona = onb = 3.3v r set = 698 ohms 100 110 120 130 140 150 160 170 180 190 200 -40 -15 10 35 60 85 t j , junction temperature (c) restart time (ms) out a outb fpf2310 in = 3.3v ona = onb = 3.3v r set = 698 ohms 1 10 100 1000 -40 -15 10 35 60 85 t j , junction temperature (c) turn on/off delay time (us) t doff t don in = 3.3v r l = 500 ohms c l = 0.1 uf r set = 698 ohms in = 3.3v r l = 500 ohms r set = 698 ohms 0 2 4 6 8 10 12 14 16 18 20 -40 -15 10 35 60 85 t j , junction temperature (c) rise/fall time (us) t f t r in = 3.3v r l = 500 ohms c l = 0.1 uf r set = 698 ohms in = 3.3v r l = 500 ohms r set = 698 ohms figure 22. t on response figure 23. t off response figure 21. t rstrt vs. temperature figure 20. t blank vs. temperature figure 18. t don / t doff vs. temperature figure 19. t rise / t fall vs. temperature
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 9 typical characteristics figure 28. output current inrush at startup with various load capacitors figure 29. output current inrush at startup with various load capacitors figure 26. current limit response with 47 f figure 24. t blank response (fpf2310/12) figure 25. t rstrt response (fpf2310) figure 27. output voltage rise time with various load capacitor out 5v/div in = 5v on = 3.3 c in = 10 f c out = 10 f r l = 3.3 ? r set = 680 ? in 5v/div on 2v/div 4ms/div i out 500ma/div out 5v/div in = 5v on = 3.3 c in = 10 f c out = 10 f r l = 3.3 ? r set = 680 ? in 5v/div on 2v/div 40ms/div i out 500ma/div in 5v/div on 2v/div 200 s/div i out 500ma/div in = 5v on = 3.3 r l = 10 ? r set = 680 ? in 5v/div on 2v/div 1ms/div out 5v/div c out = 47 f c out = 220 f c out = 100 f c out = 470 f i out 500ma/div in 5v/div on 2v/div 40 s/div in 5v/div on 2v/div 8 s/div out 5v/div in = 5v on = 3.3v c in = 10 f c out = 47 f r l = 10 ? r set = 680 ? c out = 47 f c out = 220 f c out = 100 f c out = 470 f in = 5v on = 3.3 r l = 10 ? r set = 680 ? c out = 47 f c out = 220 f c out = 100 f c out = 470 f i out 500ma/div i out 500ma/div in = 5v on = 3.3 r l = 10 ? r set = 680 ? t blank
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 10 typical characteristics figure 32. inrush response during capacitive and resistive load hot plug-in event figure 30. current limit response time both channels are in oc figure 31. inrush response during capacitive load hot plug-in event outb 500mv/div in 5v/div on 2v/div 400 s/div outa 500mv/div out 5v/div in 5v/div on 2v/div 400 s/div i out 2a/div 400 s/div in = 5v on = 3.3 c outa = 100 f c outb = 100 f r la = r lb = 1 ? r set = 680 ? in = 5v c in = 150 f c out = 47 f c l = 150 f r l = 10 ? r set = 680 ? out 5v/div in 5v/div on 2v/div i out 2a/div in = 5v c in = 150 f c out = 100 f c l = 47 f r l = 10 ? r set = 680 ?
? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 11 fpf2310/12/13/13l ? dual-output adjustable current limit switch description of operation the fpf2310/2/3/3l are dual-output current-limit switches designed to meet notebook computer, peripheral usb port, and point-of-load (pol) application power requirements. dual-output current can be used where two us b ports are powered by hosts or self-powered hubs. the fpf231x family offers control and protection while providing optimum operation current for safe design practices. the core of each switch is a 75m ? (in = 5.5v) p-channel mosfet and a controller capable of functioning over an input operating range of 1.8 to 5.5v. the fpf231x offers current limiting, uvlo (under-voltage lockout), and thermal shutdown protection in each switch. in the event of an over- current condition, the load switch limits the load to current limit value. the current limit value for each switch can be adjusted through the iset pins. 400ma-600ma is adjustable for the fpf2310 through fpf2313. the minimum current limit is 400ma-600ma with 10% accuracy at +25c with minimum variation over temperature. on/off control the on pin is active high for fpf2310/2/3 and controls the state of the switch. pulling the on pin continuous to high holds the switch in on state. the switch moves into the off state when the on pin is pulled low or if a fault is encountered. fpf2313l is active low and performs in reverse order. for all versions, an under-voltage on input voltage or a junction temperature in excess of 140c overrides the on control to turn off the switch. in addition, excessive currents cause the switch to turn off in the fpf2310 and fpf2312 after 10ms blanking time. the fpf2310 has an auto-restart feature that automatically turns the switch on again after 150ms. for the fpf2312, the on pin must be toggled to turn on the switch again. the fpf2313 and fpf2313l do not turn off in response to an over-current condition, but remain operating in a constant-current mode as long as on is enabled and the thermal shutdown or uvlo is not activated. the on pin does not have a pull-down or pull-up resistor and should not be left floating. current limiting the current limit ensures that the current through the switch doesn't exceed a maximum value, while not limiting at less than a minimum value. fpf231x family has dual-output load switches in one package. the current limit of each switch is adjustable through the an external resistor connected to the iset pin. the current limit range is from 400ma to 600ma with 10% current limit tolerance. the fpf2310 and fpf2312 have a blanking time of 10ms (t blank(typ) = 10ms) during which the switch acts as a constant current source. if the over-current condition persists beyond the blanking time, the fpf2310 latches off and shuts the switch off. if the on pin is kept active, an auto-restart feature releases the switch and turns the switch on again after a 150ms auto-restart time (t rstrt ). if the over-current condition persi sts beyond the blanking time, the fpf2312 has a latch-off feature that shuts the switch off. the switch is kept off until the on pin is toggled. the fpf2313/3l have no current-limit blanking period, so remain in a constant- current state until the on pin of the affected switch is deactivated or the thermal shutdown turns off the switch. vin on rl*ilmit vout tblank iload ilimit trstrt over current condtion figure 33. fpf2310 performance while entering into an over-current condition. note: 3. an over-current condition signal loads the output with a heavy load current larger than i lim value. vin on vout iload ilimit over current condtion thermal shut down dev ice cools o ff figure 34. fpf2313 performance while entering into an over-current condition note: 4 an over-current condition signal loads the output with a heavy load current larger than i lim value.
? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 12 fpf2310/12/13/13l ? dual-output adjustable current limit switch table 1: r set selection guide figure 35. i lim vs. r set under-voltage lockout (uvlo) the under-voltage lockout feature turns off the switch if the input voltage drops below the under-voltage lockout threshold. with the on pin is active (on pin is pulled low), the input voltage rising above the under-voltage lockout threshold causes a controlled turn-on of the switch and limits current overshoot. the device detects the uvlo condition when input voltage goes below uvlo voltage, but remains above 1.3v (typical). figure 36. under-voltage lockout (uvlo) output discharge resistor the fpf2310/2/3 and fpf2313l family contains an 70 ? on- chip output pull-down resistor for quick output discharge when the switch is turned off. this features become more attractive when an application requires a large output capacitor to be discharged when switch turns off. however, the out pin should not be connected directly to the battery source due to the discharge mechanism of the load switch. thermal shutdown the thermal shutdown protects the device from internally or externally generated excessive te mperatures. each switch has an individual thermal shutdown protection function and operates independently as adjacent switch temperature increases above 140c. if one switch is in normal operation and shutdown protection of second switch is activated, the first channel continues to operate if the affected channel's heat stays confined. the over-temperature in one channel can shut down both switches due to rapidly ge nerated excessive load currents resulting in very high power dissipation. generally, a thermally improved board layout can provide heat sinking and allow heat to stay confined and not affect operation of the second switch. during an over-temperature condition, the affected switch is turned off. if the temperature of the die drops below the threshold temperature, the switch automatically turns on again. to avoid unwanted thermal oscillations, a 10c (typical) thermal hysteresis is implemented bet ween thermal shutdown entry and exit temperatures. if output of both switches are connected together and an excessive load current activates thermal protection of both, the controller can shutdown the switches after both outputs go low and turn on both channels again. this provides a simultaneous switch turn on. thermal protection is for device protection and should not be used as regular application operation. r set [ ? ] minimum current limit [ma] typical current limit [ma] maximum current limit [ma] tolerance (%) 511 607 674 742 10 536 578 643 707 10 562 552 613 674 10 590 526 584 642 10 620 500 556 611 10 649 478 531 584 10 681 455 506 556 10 732 424 471 518 10 775 400 445 489 10 i limit (ma) r set ( ? ) device wake-up uvlo threshold on in out i load i limit 10% v out 90% v out rise time
? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 13 fpf2310/12/13/13l ? dual-output adjustable current limit switch application information figure 37. typical application fpf2310/2/3 host (5v) downstream usb port in ona ona iseta isetb outa outb gnd 33 f 1f off on off on downstream usb port 33 f input capacitor to limit the voltage drop on the input supply caused by transient inrush currents when the switch is turned on into discharged load capacitors or a short-circuit; an input capacitor, c in , is recommended between in and gnd. the fpf2310/2/3/3l features a fast current limit response time of 20 s. an inrush current (also known as surge current) could occur during the current limit response time while the switch is responding to an over-current condition caused by large output capacitors. a 10 f ceramic capacitor, c in , is required to pr ovide charges for the inrush current and prevent input voltage drop at the turn on. higher values of c in to further reduce the voltage drop. output capacitor a 0.1 f to 1 f capacitor, c out , should be placed between the out and gnd pins. this capacitor prevents parasitic board inductances from forcing output voltage below gnd when the switch turns off. this capacitor should have a low dissipation factor. an x7r mlcc (multilayer ceramic chip) capacitors is recommended. for the fpf2310 and fpf2312, the total output capacitance needs to be kept below a maximum value, c out(max) , to prevent the part from regist ering an over-current condition beyond the blanking time and shutdown. the maximum output capacitance for a giving input voltage can be determined from the following: for example, in a 5v application and i lim(min) = 500ma using r set = 620 ? , c out(max) can be determine as: power dissipation during normal operation as a switch, the power dissipation of device is small and has little effect on the operating temperature of the part. the maximum power dissipation for both switches, while the switch is in normal operation, occurs just before both channels enter into current limit. this may be calculated using: for example, for a 5v application maximum normal operation power loss while both switches delivering output current up to 500ma (i lim(min) = 500ma) can be calculated as: the maximum junction temperature should be limited to 125c under normal operation. junction temperature can be calculated using: where: t j is junction temperature; p d is power dissipation across the switch r ja is thermal resistance, junction-to-ambient; and t a is ambient temperature for example, t j(max)(normal operation) for an mlp 3x3mm package with t a =25c while both switches are delivering up to 1.1a, is calculated as: (2) c out(max) = i lim(min) x t blank(min) v in (3) c out(max)(in = 5v) = 0.5a x 5ms 5 = 500 f p d_max(normaloperation) = 2 x (i lim(min) ) 2 x r on(max) (4) p d_max(normaloperation)(in = 5v) = 2 x (0.5) 2 x 0.14 = 70mw (5) t j = p d x r ja + t a (6) t j(max)(normaloperation) = p d_max(normal operation)(in = 5v) x 216 + 25 = 40.12c (7)
? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 14 fpf2310/12/13/13l ? dual-output adjustable current limit switch fpf2310/2/3 host (5v) downstream usb port in ona ona iseta isetb outa outb gnd 33 f 1f off on off on if the part goes into current limit, the maximum power dissipation occurs when the output of switch is shorted to ground. for the fpf2310, the power dissipation scales with the auto-restart time, t rstrt , and the over-current blanking time, t blank . in this case, the maximum power dissipated for the fpf2310 is: which results in: note that this is below the maximum package power dissipation and the thermal shutdown featur e protection provides additional safety to protect the part from damage due to excessive heating. the junction temperature is only able to increase to the thermal shutdown threshold. once this temperature has been reached, toggling on has no effect until the junction temperature drops below the thermal shutdown exit temperature. for the fpf2313 and fpf2313l, a short on the both outputs causes both switc hes to operate in a constant- current state and dissipating a worst-case power of: as both fpf2313/3l outputs are connected to gnd. this power dissipation is significant and activates both thermal shutdown blocks. the part cycles in and out of thermal shutdown as long as the on pin is activated (pulled low) and the output short is present. if high current of over 1a is required to supply enough power to a downstream function, dual outputs can be tied together as shown in figure 38. pcb layout recommendations for the best performance, all traces should be as short as possible. to be most effective, the input and output capacitors should be placed close to the device to minimize the effects that parasitic trace inductances may have on normal and short- circuit operation. using wide traces for in, outs, and gnd pins helps minimize parasitic electrical effects along with minimizing the case-to-ambient thermal impedance. improving thermal performance of the fpf231x family of devices improper layout could result in higher junction temperature and triggering the thermal shutdown protection feature. this concern applies particularly to the fpf2313 and fpf2313l, where both channels operate in constant-cur rent mode in the overload conditions and; during fault condition, the outputs are shorted, resulting to large voltage drop across switches. in this case, power dissipation of the switch (p d = (v in - v out ) x i lim(max) ) could exceed the maximum absolute power dissipation of part. the following techniques improve the thermal performance of this family of devices. these techniques are listed in order of the significance of impact. 1. thermal performance of the load switch can be improved by connecting the dap (die attach pad) of mlp 3x3mm package to the gnd plane of the pcb. 2. embedding two exposed through-hole vias into the dap (pin 9) provides a path for heat to transfer to the back gnd plane of the pcb. a drill size of round, 15 mils (0.4mm) with 1- ounce copper plating is recommended to create appropriate solder reflow. a smaller size hole prevents the solder from penetrating into the via, resulting in device lift-up. similarly, a larger via-hole consumes excessive solder and may result in voiding the dap. p d_max(currentlimit) = 2 x t blank t blank + t rstrt x in (max) x i lim(max) (8) p d_max(currentlimit) = 10 10 + 150 2 x x 5.5 x 0.74 = 508mw (9) (10) p max = in (max) x i lim(max) = 2 x 5.5 x 0.74 = 8.14w figure 38. self-power usb for high current demand
? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 15 fpf2310/12/13/13l ? dual-output adjustable current limit switch figure 39. two through-hole open vias embedded in dap 3. the in, outs, and gnd pins dissipate most of the heat generated during a high-load current condition. the layout suggested in figure 39 illustrate s a proper layout for devices in mlp 3x3mm packages. in, outs, and gnd pins are connected to adequate copper so that heat may be transferred as efficiently as possible out of the device. the low-power flagb and on pins? traces may be laid-out diagonally from the device to maximize the area available to the ground pad. placing the input and output capacitors as close to the device as possible also contributes to heat dissipation, particularly during high load currents. figure 40. proper layout of output and ground copper area fpf231x evaluation board fpf231x evaluation board has components and circuitry to demonstrate fpf2310/2/3/3l load switches functions and features accommodating both mlp 3x3mm packages. the state of the each channel can be configured using j1 and j2 jumpers. in addition, both channels can be controlled by ona and onb test pins. thermal performance of the board is improved using techniques recommended in the layout recommendations section. r3 and r4 resistors are used on the board to sink a light load current when switches are activated. figure 41. top, sst, and ast layers (mlp 3x3mm package) figure 42. zoom in to top layer figure 43. bottom and asb layers 15mil 25mil
? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 16 fpf2310/12/13/13l ? dual-output adjustable current limit switch dimensional outline and pad layout figure 44. 8-lead molded leadless package (mlp) package drawings are provided as a servic e to customers considering fairchild co mponents. drawings may change in any manner without notice. please note the revision and/or date on the drawi ng and contact a fairchild semic onductor representative to ver ify or obtain the most recent revision. package specifications do not expand the terms of fairchild?s worldwide terms and conditions, specifically the warranty therein, which covers fairchild products. always visit fairchild semiconductor?s online packagi ng area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ .
fpf2310/12/13/13l ? dual-output adjustable current limit switch ? 2009 fairchild semiconductor corporation www.fairchildsemi.com fpf2310/12/13/13l ? rev. 1.1.3 17

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