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LTC4358 1 4358fa features applications description 5a ideal diode the ltc ? 4358 is a 5a ideal diode that uses an internal 20m n-channel mosfet to replace a schottky diode when used in diode-or and high current diode applica- tions. the LTC4358 reduces power consumption, heat dissipation, and pc board area. the LTC4358 easily ors power supplies together to in- crease total system reliability. in diode-or applications, the LTC4358 regulates the forward voltage drop across the internal mosfet to ensure smooth current transfer from one path to the other without oscillation. if the power source fails or is shorted, a fast turnoff minimizes reverse current transients. 12v, 5a diode-or n replaces a power schottky diode n internal 20m n-channel mosfet n 0.5s turn-off time limits peak fault current n operating voltage range: 9v to 26.5v n smooth switchover without oscillation n no reverse dc current n available in 14-pin (4mm 3mm) dfn and 16-lead tssop packages n n+1 redundant power supplies n high availability systems n telecom infrastructure n automotive systems power dissipation vs load current 4358 ta01 LTC4358 gnd in drain v dd out v ina = 12v v out to 5a load LTC4358 gnd in drain v dd out v inb = 12v current (a) 0 0 power dissipation (w) 0.5 1.0 1.5 2.0 2.5 3.0 24 6 8 4358 ta01b diode (b530c) power saved fet (LTC4358) l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. typical application
LTC4358 2 4358fa absolute maximum ratings supply voltages in, out, v dd , drain voltage ................. C0.3v to 28v output voltage gate (note 3) .......................... v in C 0.2v to v in + 6v operating ambient temperature range LTC4358c ................................................ 0c to 70c LTC4358i.............................................. C40c to 85c (notes 1, 2) 1 2 3 4 5 6 7 14 13 12 11 10 9 8 in in in in nc out v dd in in in in gate nc gnd top view 15 drain de package 14-lead (4mm s 3mm) plastic dfn t jmax = 125c, jc = 4c/w, ja = 43c/w fe package 16-lead plastic tssop 1 2 3 4 5 6 7 8 top view 16 15 14 13 12 11 10 9 in in in in nc gate nc gnd in in in in in nc out v dd 17 drain t jmax = 125c, jc = 10c/w, ja = 38c/w storage temperature range ................... C65c to 150c lead temperature (soldering, 10 sec) fe package ....................................................... 300c lead free finish tape and reel part marking* package description temperature range LTC4358cde#pbf LTC4358cde#trpbf 4358 14-lead (4mm 3mm) plastic dfn 0c to 70c LTC4358ide#pbf LTC4358ide#trpbf 4358 14-lead (4mm 3mm) plastic dfn C40c to 85c LTC4358cfe#pbf LTC4358cfe#trpbf 4358fe 16-lead plastic tssop 0c to 70c LTC4358ife#pbf LTC4358ife#trpbf 4358fe 16-lead plastic tssop C40c to 85c consult ltc marketing for parts speci? ed with wider operating temperature ranges. *temperature grades are identi? ed by a label on the shipping container. consult ltc marketing for information on non-standard lead based ? nish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/ order information pin configuration
LTC4358 3 4358fa electrical characteristics note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v out = v dd , v dd = 9v to 26.5v, unless otherwise noted. symbol parameter conditions min typ max units v dd operating supply range l 926.5v i dd operating supply current l 0.6 ma i in in pin current v in = v out 1v, no load l 150 350 450 a i out out pin current v in = v out 1v, no load l 80 160 a i drain drain pin current v in = 0v, v out = v dd = v drain = 26.5v l 5 150 a a v gate n-channel gate drive (v gate C v in )v dd, v out = 9v to 26.5v l 4.5 15 v i gate(up) n-channel gate pull up current v gate = v in, v in C v out = 0.1v l C14 C20 C26 a i gate(down) n-channel gate pull down current in fault condition v gate = v in + 5v l 12 a t on turn-on time v in C v out = C1v C | C 0.1v, v drain = v in , v out = v dd, v gate C v in > 4.5v l 200 500 s t off turn-off time v in C v out = 55mv C | C C1v, v drain = v in , v out = v dd, v gate C v in < 1v l 300 500 ns v sd source-drain regulation voltage (v in C v out ) 1ma < i in < 100ma l 10 25 55 mv v sd body diode forward voltage drop i in = 5a, mosfet off l 0.6 0.8 1 v r ds(on) internal n-channel mosfet on resistance i in = 5a l 20 40 m note 2: all currents into pins are positive, all voltages are referenced to gnd unless otherwise speci? ed. note 3: an internal clamp limits the gate pin to a minimum of 6v above in. driving this pin to voltages beyond this clamp may damage the device.
LTC4358 4 4358fa typical performance characteristics v out (v) 0 i out (a) 80 100 4358 g03 60 40 20 0 10 20 30 v in = v out = v dd temperature (?c) -50 r ds(on) (m) 20 25 30 4358 g04 15 10 5 0 -25 0 25 75 50 125 100 v out = v dd = 9v i in = 5a v out = v dd = 26.5v 0 t pd (ns) 300 400 4358 g05 200 100 0 0.2 0.6 0.8 0.4 1 v in = 12v $ v sd = v initial -1v v initial (v) v final (v) 0 t pd (ns) 1500 2000 4358 g06 1000 500 0 -0.2 -0.6 -0.8 -0.4 -1 v in = 12v $ v sd = 55mv v final v dd current (i dd vs v dd ) in current (i in vs v in ) out current (i out vs v out ) mosfet r ds(on) vs temperature fet turn-off time vs initial overdrive fet turn-off time vs final overdrive v dd (v) 0 i dd (a) 300 400 4358 g01 200 100 0 10 20 30 500 v in = v out = v dd v in (v) 0 i in (a) 300 400 4358 g02 200 100 0 10 20 30 v in = v out = v dd
LTC4358 5 4358fa pin functions drain: the exposed pad is the drain of the internal n-channel mosfet. this pin must be connected to out (pin 9/pin 10). gate: gate drive output. if reverse current ? ows, a fast pulldown circuit quickly connects the gate pin to the in pin, turning off the mosfet. leave open if unused. gnd: device ground. in: input voltage and fast pulldown return. in is the anode of the ideal diode. the voltage sensed at this pin is used to control the source-drain voltage drop across the internal mosfet. if reverse current starts to ? ow, a fast pulldown circuit quickly turns off the internal mosfet. the fast pulldown current is returned through this pin. nc: no connection. not internally connected. out: output voltage. the out pin is the cathode of the ideal diode and the common output when multiple LTC4358s are con? gured as an ideal diode-or. the voltage sensed at this pin is used to control the source-drain voltage drop across the mosfet. connect this pin to the drain of the internal n-channel mosfet (pin 15/pin 17). v dd : positive supply input. the LTC4358 is powered from the v dd pin. connect this pin to out either directly or through an rc hold-up circuit. (de/fe packages) 4358 bd charge pump ? + ? + + ? fpd comp gate amp 25mv 25mv in out drain gate gnd in v dd + ? block diagram
LTC4358 6 4358fa operation high availability systems often employ parallel-connected power supplies or battery feeds to achieve redundancy and enhance system reliability. oring diodes have been a popular means of connecting these supplies at the point of load. the disadvantage of this approach is the forward voltage drop and resulting ef? ciency loss. this drop reduces the available supply voltage and dissipates signi? cant power. using an n-channel mosfet to replace a schottky diode reduces the power dissipation and eliminates the need for costly heat sinks or large thermal layouts in high power applications. the LTC4358 is a single positive voltage ideal diode con- troller that drives an internal n-channel mosfet as a pass transistor to replace a schottky diode. the in and drain pins form the anode and cathode of the ideal diode. the input supply is connected to the in pins, while the drain pin serves as the output. the out pin is connected directly to drain and v dd . v dd is the supply for the LTC4358 and is derived from the output either directly or through an rc hold-up circuit. at power-up, the load current initially ? ows through the body diode of the internal mosfet. the internal mosfet turns on and the ampli? er tries to regulate the voltage drop across the in and out connections to 25mv. if the load current causes more than 25mv of drop, the mosfet is driven fully on and the voltage drop is equal to r ds(on) ? i load . if the load current is reduced causing the forward drop to fall below 25mv, the internal mosfet is driven lower by a weak pull-down in an attempt to maintain the drop at 25mv. if the load current reverses the mosfet is turned off with a strong pull-down. in the event of a power supply failure, such as if the sup- ply that is conducting most or all of the current is shorted to ground, reverse current temporarily ? ows through the LTC4358 ideal diode that is on. this current is sourced from any load capacitance and from the other supplies. the ideal diode is turned off within 500ns, preventing reverse current from slewing up to a damaging level and minimizing any disturbance on the output.
LTC4358 7 4358fa applications information oring two supply outputs where LTC4358s are used to combine the outputs of two supplies, the power supply with the highest output voltage sources most or all of the current. if this supplys output is quickly shorted to ground while delivering load current, the current temporarily reverses and ? ows backwards through the LTC4358. when reverse current ? ows the LTC4358 ideal diode is quickly turned off. if the other initially lower supply was not delivering load current at the time of the fault, the output falls until the LTC4358 body diode conducts. meanwhile, the internal ampli? er turns on the mosfet until the forward drop is reduced to 25mv. if instead this supply was delivering load current at the time of the fault, its oring mosfet was already driven at least partially on, and will be driven harder in an effort to maintain a drop of 25mv. load sharing figure 1 combines the outputs of multiple, redundant supplies using a simple technique known as droop sharing. load current is ? rst taken from the highest output, with the low outputs contributing as the output voltage falls under increased loading. the 25mv regulation technique ensures smooth load sharing between outputs without oscillation. the degree of sharing depends on the 20m resistance of the LTC4358 internal mosfet, the output impedance of the supplies and their initial output voltages. LTC4358 gnd in ps1 drain v dd out rtna v ina = 12v 12v bus LTC4358 gnd in drain v dd out ps2 rtnb v inb = 12v ps3 rtnc v inc = 12v 4358 f01 LTC4358 gnd in drain v dd out figure 1. droop sharing redundant supplies
LTC4358 8 4358fa applications information figure 3. C12v reverse input protection LTC4358 gnd in drain v dd out v in = 12v c load c1 0.1f r1 100 v out 12v 5a 4358 f03 mmbd1205 v dd hold-up circuit in the event of an input short, parasitic inductance between the input supply of the LTC4358 and the load bypass capacitor may cause v dd to glitch below its minimum operating voltage. this causes the turn-off time (t off ) to increase. to preserve the fast turn-off time, local output bypassing of 39f or more is suf? cient or a 100, 0.1f rc hold-up circuit on the v dd pin can be used as shown in figure 2a and figure 2b. layout considerations the following advice should be considered when laying out a printed circuit board for the LTC4358: the out pin should figure 2. two methods of protecting against collapse of v dd from input short and stray inductance 4358 f02 LTC4358 gnd in drain v dd out v in = 12v LTC4358 gnd in drain v dd out v in = 12v r1 100 7 c1 0.1 m f c bypass 39 m f v out v out (a) (b) be connected as closely as possible to the exposed pad (drain of the mosfet) for good accuracy. keep the traces to the in and drain wide and short. the pcb traces as- sociated with the power path through the mosfet should have low resistance. see figure 4. the drain acts as a heatsink to remove the heat from the device. for a single layer pcb with the dfn package, use figure 5 to determine the pcb area needed for a speci- ? ed maximum current and ambient temperature. if using a two sided pcb, the maximum current is increased by 10%. if the fe package is used, the maximum current is increased by 4%.
LTC4358 9 4358fa diode current (a) 3.5 area (inch 2 ) 4.5 10 4358 f05 0.1 1 4.0 6.5 6.0 5.5 5.0 3.0 85 o c 70 o c 25 o c t a = 50 o c figure 5. maximum diode current vs pcb area applications information v in gnd v out figure 4. dfn layout considerations for 1 1 single sided pcb
LTC4358 10 4358fa de package 14-lead plastic dfn (4mm 3mm) (reference ltc dwg # 05-08-1708) package description 3.00 0.10 (2 sides) 4.00 0.10 (2 sides) note: 1. drawing proposed to be made variation of version (wged-3) in jedec package outline mo-229 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.40 0.10 bottom view?exposed pad 1.70 0.10 0.75 0.05 r = 0.115 typ r = 0.05 typ 3.00 ref 1.70 0.05 1 7 14 8 pin 1 top mark (see note 6) 0.200 ref 0.00 ? 0.05 (de14) dfn 0 8 06 rev b pin 1 notch r = 0.20 or 0.35 45 chamfer 3.00 ref recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 2.20 0.05 0.70 0.05 3.60 0.05 package outline 0.25 0.05 0.25 0.05 0.50 bsc 3.30 0.05 3.30 0.10 0.50 bsc
LTC4358 11 4358fa information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description fe package 16-lead plastic tssop (4.4mm) (reference ltc dwg # 05-08-1663) exposed pad variation bc fe16 (bc) tssop 0204 0.09 ? 0.20 (.0035 ? .0079) 0 ? 8 0.25 ref 0.50 ? 0.75 (.020 ? .030) 4.30 ? 4.50* (.169 ? .177) 134 5 6 7 8 10 9 4.90 ? 5.10* (.193 ? .201) 16 1514 13 12 11 1.10 (.0433) max 0.05 ? 0.15 (.002 ? .006) 0.65 (.0256) bsc 2.94 (.116) 0.195 ? 0.30 (.0077 ? .011 8 ) typ 2 recommended solder pad layout 0.45 0.05 0.65 bsc 4.50 0.10 6.60 0.10 1.05 0.10 2.94 (.116) 3.5 8 (.141) 3.5 8 (.141) millimeters (inches) *dimensions do not include mold flash. mold flash shall not exceed 0.150mm (.006") per side note: 1. controlling dimension: millimeters 2. dimensions are in 3. drawing not to scale see note 4 4. recommended minimum pcb metal size for exposed pad attachment 6.40 (.252) bsc
LTC4358 12 4358fa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2007 lt 0808 rev a ? printed in usa typical application plug-in card input diode for supply hold-up plug-in card connector 1 backplane connectors plug-in card connector 2 12v v out1 c holdup v out2 gnd gnd 4358 ta02 LTC4358 gnd in out v dd 100 0.1f LTC4358 gnd in out v dd 100 0.1f hot swap controller hot swap controller + c holdup + part number description comments lt1640ah/lt1640al negative high voltage hot swap? controllers in so-8 negative high voltage supplies from C10v to C80v lt1641-1/lt1641-2 positive high voltage hot swap controllers active current limiting, supplies from 9v to 80v lt4250 C48v hot swap controller active current limiting, supplies from C20v to C80v ltc4251/ltc4251-1/ ltc4251-2 C48v hot swap controllers in sot-23 fast active current limiting, supplies from C15v ltc4252-1/ltc4252-2/ ltc4252-1a/ltc4252-2a C48v hot swap controllers in ms8/ms10 fast active current limiting, supplies from C15v, drain accelerated response ltc4253 C48v hot swap controller with sequencer fast active current limiting, supplies from C15v, drain accelerated response, sequenced power good outputs lt4256 positive 48v hot swap controller with open-circuit detect foldback current limiting, open-circuit and overcurrent fault output, up to 80v supply ltc4260 positive high voltage hot swap controller with i 2 c and adc, supplies from 8.5v to 80v ltc4261 negative high voltage hot swap controller with i 2 c and 10-bit adc, adjustable inrush and overcurrent limits ltc4350 hot swappable load share controller output voltage: 1.2v to 20v, equal load sharing lt4351 mosfet diode-or controller external n-channel mosfets replace oring diodes, 1.2v to 20v ltc4352 ideal diode controller with monitor controls n-channel mosfet, 0v to 18v operation ltc4354 negative voltage diode-or controller and monitor controls two n-channel mosfets, 1s turn-off, 80v operation ltc4355 positive voltage diode-or controller and monitor controls two n-channel mosfets, 0.5s turn-off, 80v operation ltc4357 positive high voltage ideal diode controller controls single n-channel mosfet, 0.5s turn-off, 80v operation ltc4223-1/ltc4223-2 dual supply hot swap controller for advanced mezzanine cards and tca controls 12v main and 3.3v auxiliary supplies hot swap is a trademark of linear technology corporation. related parts

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