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ZXGD3105N8 document number ds35101 rev. 1 ? 2 1 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 synchronous mosfet co ntroller in so-8 description ZXGD3105N8 synchronous controller is designed for driving a mosfet as an ideal rectifier. this is to replace a diode for increasing the power transfer efficiency. the device is comprised of a diffe rential amplifier detector stage and high current driver. the detector m onitors the reverse voltage of the mosfet such that if body diode conduction occurs a positive voltage is applied to the mosfet?s gate pin. once the positive voltage is applied to the gate the mosfet switches on allowing reverse current flow. the detectors? output voltage is then proportional to the mosfet drain-source voltage and this is applied to the gate via the driver. this action provi des a rapid mosfet turn off as drain current decays to zero. applications flyback and resonant converters in: ? low voltage ac / dc adaptors ? set top box ? computing power supplies - atx and server psu ? low voltage dc / dc conversion features ? low standby power with quiescent supply current < 1ma ? 4.5v operation enables low voltage supply ? proportional gate drive for fast turn-off ? operation up to 500khz ? critical conduction mode (crcm) & continuous mode (ccm) ? compliant with eco-design directive ? ?lead-free?, rohs compliant (note 1) ? halogen and antimony free. ?green? device (note 2) ? qualified to aec-q101 standards for high reliability mechanical data ? case: so-8 ? case material: molded plasti c. ?green? molding compound. ? ul flammability rating 94v-0 ? moisture sensitivity: level 1 per j-std-020 ? terminals: matte tin finish ? solderable per mil-std-202, method 208 ? weight: 0.074 grams (approximate) ordering information (note 3) product marking reel size (inches) tape width (mm) quantity per reel ZXGD3105N8tc zxgd 3105 13 12 2500 notes: 1. no purposefully added lead 2. diodes inc?s ?green? policy can be found on our website at http://www.diodes.com 3. for packaging details, go to our website at http://www.diodes.com marking information zxgd = product type marking code, line 1 3105 = product type marking code, line 2 yy = year (ex: 11 = 2011) ww = week (01 - 53) top view pin-out so-8 zxgd 3105 y y w w gate gnd vcc bias drain ref dnc dnc
ZXGD3105N8 document number ds35101 rev. 1 ? 2 2 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 functional block diagram pin # pin name pin function and description 1 vcc power supply this supply pin should be cl osely decoupled to ground with a ceramic capacitor. 2 dnc do not connect leave pin floating. 3 bias bias connect this pin to vcc via r bias resistor. select r bias to source 0.54ma into this pin. refer to table 1 and 2, in application information section. 4 drain drain sense connect directly to the synchronous mosfet drain terminal. 5 ref reference connect this pin to vcc via r ref resistor. select r ref to source 1.02ma into this pin. refer to table 1 and 2, in application information section. 6 dnc do not connect leave pin floating. 7 gnd ground connect this pin to the synchronous mosfet source terminal and ground reference point. 8 gate gate drive this pin sinks and sources the i sink and i source current to the synchronous mosfet gate.
ZXGD3105N8 document number ds35101 rev. 1 ? 2 3 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 maximum ratings @t a = 25c unless otherwise specified characteristic symbol value unit supply voltage, relative to gnd v cc 15 v drain pin voltage v d -3 to 100 v gate output voltage v g -3 to v cc + 3 v gate driver peak source current i source 4 a gate driver peak sink current i sink 9 a reference voltage v ref v cc v reference current i ref 25 ma bias voltage v bias v cc v bias current i bias 100 ma thermal characteristics @t a = 25c unless otherwise specified characteristic symbol value unit power dissipation linear derating factor (note 4) p d 490 3.92 mw mw/ c (note 5) 655 5.24 (note 6) 720 5.76 (note 7) 785 6.28 thermal resistance, junction to ambient (note 4) r ja 255 c/w (note 5) 191 (note 6) 173 (note 7) 159 thermal resistance, junction to lead (note 8) r jl 135 c/w operating temperature range t j -40 to +150 c storage temperature range t stg -50 to +150 notes: 4. for a device surface mounted on minimum recommended pad layout fr4 pcb with high coverage of single sided 1oz copper, in still air conditions; the device is measured when operating in a steady-state condition. 5. same as note (4), except pin 1 (v cc ) and pin 7 (gnd) are both connected to separate 5mm x 5mm 1oz copper heatsinks. 6. same as note (5), except both heatsinks are 10mm x 10mm. 7. same as note (5), except both heatsinks are 15mm x 15mm. 8. thermal resistance from junction to solder-point at the end of each lead on pin 1 (v cc ) and pin 7 (gnd).
ZXGD3105N8 document number ds35101 rev. 1 ? 2 4 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 thermal derating curve 0 20 40 60 80 100 120 140 160 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 15mm x 15mm 5mm x 5mm minimum layout derating curve junction temperature (c) max power dissipation (w) 10mm x 10mm esd rating characteristic value unit esd for human body model 4000 v esd for machine model 200
ZXGD3105N8 document number ds35101 rev. 1 ? 2 5 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 electrical characteristics @t a = 25c unless otherwise specified v cc = 10v; r bias = 18k ? (i bias = 0.54ma); r ref = 9.1k ? (i ref = 1.02ma) characteristic symbol min typ max unit test condition input supply quiescent current i q - 1.56 - ma v drain 0mv gate driver gate peak source current i source - 2 - a capacitive load: c l = 20nf gate peak sink current i sink - 7 - detector under dc condition turn-off threshold voltage v t -20 -10 0 mv v g = 1v capacitive load only gate output voltage v g ( off ) - 0.2 0.6 v v drain 1v v g 5.0 7.8 v drain = -50mv 8.0 9.4 v drain = -100mv switching performance turn-on propagation delay t d ( rise ) - 70 - ns rise and fall measured 10% to 90% refer to application test circuit below gate rise time t r - 175 - turn-off propagation delay t d ( fall ) - 15 - gate fall time t f - 20 -
ZXGD3105N8 document number ds35101 rev. 1 ? 2 6 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 typical electrical characteristics @t a = 25c unless otherwise specified -100 -80 -60 -40 -20 0 0 2 4 6 8 10 12 14 -100 -80 -60 -40 -20 0 0 2 4 6 8 10 -50 0 50 100 150 -30 -25 -20 -15 -10 -5 0 -50 -25 0 25 50 75 100 125 150 30 35 130 140 150 160 170 180 190 200 210 220 230 0 2 4 6 8 10121416182022 0 20 40 60 80 100 120 140 160 180 -100 -80 -60 -40 -20 0 0 2 4 6 8 10 12 14 v cc = 5v capacitive load and 50k pull down v cc = 15v v cc = 12v v cc = 10v transfer characteristic v g gate voltage (v) v d drain voltage (mv) t a = -40c t a = 25c t a = 125c transfer characteristic v g gate voltage (v) v d drain voltage (mv) v cc = 10v r bias =18k r ref =9.1k 50k pull down v cc = 10v r bias =18k r ref =9.1k v g = 1v 50k pull down turn-off threshold voltage vs temperature turn-off threshold voltage (mv) temperature (c) t off = t d(fall) + t f t on = t d(rise) + t r switching vs temperature switching time (ns) temperature (c) v cc = 10v r bias =18k r ref =9.1k c l =10nf v cc = 5v v cc = 10v v cc = 12v v cc = 15v supply current vs capacitive load capacitance (nf) supply current (ma) r bias =18k r ref =9.1k f=500khz capacitive load only v cc = 5v v cc = 15v v cc = 12v v cc = 10v transfer characteristic v g gate voltage (v) v d drain voltage (mv)
ZXGD3105N8 document number ds35101 rev. 1 ? 2 7 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 continued - typical el ectrical characteristics @t a = 25c unless otherwise specified -100 0 100 200 300 -2 0 2 4 6 8 10 -200 -100 0 100 200 300 -2 0 2 4 6 8 10 11 01 0 0 10 100 0 200 400 600 -8 -6 -4 -2 0 2 4 11 01 0 0 0 2 4 6 8 10 10 100 1000 10000 100000 1 10 100 v cc =10v r bias =18k r ref =9.1k c l =10nf r l =0.1 v d switch on speed voltage (v) time (ns) v g v cc =10v r bias =18k r ref =9.1k c l =10nf r l =0.1 v g v d switch off speed voltage (v) time (ns) v cc =10v r bias =18k r ref =9.1k r l =0.1 t on = t d(rise) + t r t off = t d(fall) + t f switching vs capacitive load time (ns) capacitance (nf) v cc =10v r bias =18k r ref =9.1k c l =10nf r l =0.1 i source i sink gate drive current gate drive current (a) time (ns) v cc =10v r bias =18k r ref =9.1k r l =0.1 -i sink gate current vs capacitive load peak drive current (a) capacitance (nf) i source c l =100nf c l =33nf c l =10nf c l =3.3nf c l =1nf v cc =10v r bias =18k r ref =9.1k r l =0.1 supply current vs frequency frequency (hz) supply current (ma)
ZXGD3105N8 document number ds35101 rev. 1 ? 2 8 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 application information the purpose of the zxgd3105 is to drive a mosfet as a low-v f schottky diode replacement in isolated ac/dc converter. when combined with a low r ds(on) mosfet, the controller can yiel d significant power efficiency improvement, whilst maintaining design simplicity and incurr ing minimal component count. figure 1 shows the typical configuration of zxgd3105 for sy nchronous rectification in a low output voltage flyback converter. figure 1 - typical flyback application schematic threshold voltage and resistor setting proper selection of external resistors r ref and r bias is important for optimum device operation. r ref and r bias supply fixed current into the i ref and i bias pin of the controller. i ref and i bias combines to set the turn-off threshold voltage level, v t . in order to set v t to -10mv, the recommended i ref and i bias are 1.02ma and 0.54ma respectively. the values for r ref and r bias are selected based on the vcc voltage. if the vcc pin is connected to the power converter?s output, the resistors should be selected bas ed on the nominal converter?s output voltage. table 1 provides the recommended resistor values for different vcc voltages. supply, vcc bias resistor, r bias reference resistor, r ref 5 v 9.6 k ? 4.3 k ? 10 v 18 k ? 9.1 k ? 12 v 24 k ? 11 k ? 15 v 30 k ? 15 k ? table 1 ? recommended resistor values for different vcc voltages
ZXGD3105N8 document number ds35101 rev. 1 ? 2 9 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 functional descriptions the operation of the device is desc ribed step-by-step with reference to the timing diagram in figure 2. 1. the detector stage monitors the mosfet drain-source voltage. 2. when, due to transformer action, the mosfet body diode is forced to conduct there is a negative voltage on the drain pin due to the body diode forward voltage. 3. when the negative drain voltage cros ses the turn-off threshold voltage v t , the detector stage outputs a positive voltage with respect to ground after the turn-on delay time t d(fall) . this voltage is then fed to the mosfet driver stage and current is sourced out of the gate pin. 4. the controller goes into proportional gate drive cont rol ? the gate output voltage is proportional to the mosfet on-resistance-induced drain- source voltage. proportional gate drive ensures that mosfet conducts during majority of the conduction cycle to minimize power loss in the body diode. 5. as the drain current decays linearly toward zero, proportional gate drive control reduces the gate voltage so the mosfet can be turned off rapidly at zero curr ent crossing. the gate voltage falls to 1v when the drain-source voltage crosses the detection threshol d voltage to minimize reverse current flow. 6. at zero drain current, the controlle r gate output voltage is pulled low to v g(off) to ensure that the mosfet is off. 10% t r t d(rise) v t 90% t f mosfet drain voltage 0a 90% v g(off) body diode conduction t d(fall) 10% v d mosfet gate voltage mosfet drain current v g i d 1 2 3 4 5 6 figure 2 - timing diagram for a critical conduction mode flyback converter
ZXGD3105N8 document number ds35101 rev. 1 ? 2 10 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 gate driver the controller is provided with single channel high curre nt gate drive output, capable of driving one or more n- channel power mosfets. the controller can operate from vcc of 4.5v to drive both standard mosfets and logic level mosfets. the gate pins should be as close to the mosfet?s gate as possible. a resistor in series with gate pin helps to control the rise time and decrease switching losses due to gate voltage oscillation. a diode in parallel to the resistor is typically used to maintain fast discharge of the mosfet?s gate. figure 3 - typical connection of the zxgd 3105 to the synchronous mosfet quiescent current consumption the quiescent current consumption of the controller is the sum of i ref and i bias . for an application that requires ultra- low standby power consumption, i ref and i bias can be further reduced by incr easing the value of resistor r ref and r bias . bias current i bias re f current i ref bias resistor r bias ref resistor r ref quiescent current i q 0.25ma 0.61ma 39.2k ? 15.4k ? 0.86ma 0.35ma 0.81ma 28.0k ? 11.5k ? 1.16ma 0.46ma 0.99ma 21.5k ? 9.3k ? 1.45ma 0.50ma 1.00ma 19.6k ? 8.9k ? 1.50ma 0.55ma 1.13ma 17.8k ? 8.1k ? 1.68ma 0.80ma 1.66ma 12.1k ? 5.6k ? 2.46ma table 2 ? quiescent current consumption for different resistor values at vcc=10v i ref also controls the gate driver peak sink current whilst i bias controls the peak source current. at the default current value of i ref and i bias of 1.02ma and 0.54ma, the gate driver is able to provide 2a source and 6a sink current. the gate current decreases if i ref and i bias are reduced. care must be taken in re ducing the controller quiescent current so that sufficient drive curr ent is still delivered to the mosfet particula rly for high switching frequency application.
ZXGD3105N8 document number ds35101 rev. 1 ? 2 11 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 layout guidelines when laying out the pcb, care must be taken in decoupling the zxgd3105 closely to v cc and ground with 1 f low- esr, low-esl x7r type ceramic bypass capacitor. if the c onverter?s output voltage is higher than 15v, a series voltage regulator between the converter?s output voltage and the vcc pin, can be used to get a stable vcc voltage. gnd is the ground reference for the internal high voltage amplif ier as well as the current return for the gate driver. so the ground return loop should be as short as possible. sufficient pcb copper area should be allocated to the vcc and gnd pin for heat dissipation especially for high switching frequency application. any stray inductance involved by the load current may ca use distortion of the drain-to-source voltage waveform, leading to premature turn-off of the synchronous mosfet. in order to avoid this issue, drain voltage sensing should be done as physically close to the drain terminals as possible. the pcb track length between the controller drain pin and mosfet?s terminal should be kept less than 10mm. mo sfet packages with low internal wire bond inductance are preferred for high switching frequency power conversion to minimize body diode conduction. after the primary mosfet turns off, its drain voltage oscillates due to reverse recovery of the snubber diode. these high frequency oscillations are reflected across the transform er to the drain terminal of the synchronous mosfet. the synchronous controller senses the drain voltage ring ing, causing its gate output voltage to oscillate. the synchronous mosfet cannot be fully enhan ced until the drain voltage stabilizes. in order to prevent this issue, the os cillations on the primary mosfet can be damped with either a series resistor rd to the snubber diode or an r-c network across the diode. both methods reduce the oscillations by softening the snubber diode?s reverse recovery characteristic. figure 4 - primary side snubber network to r educe drain voltage oscillations
ZXGD3105N8 document number ds35101 rev. 1 ? 2 12 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 package outline dimensions dim inches millimeters dim inches millimeters min. max. min. max. min. max. min. max. a 0.053 0.069 1.35 1.75 e 0.050 bsc 1.27 bsc a1 0.004 0.010 0.10 0.25 b 0.013 0.020 0.33 0.51 d 0.189 0.197 4.80 5.00 c 0.008 0.010 0.19 0.25 h 0.228 0.244 5.80 6.20 0 8 0 8 e 0.150 0.157 3.80 4.00 h 0.010 0.020 0.25 0.50 l 0.016 0.050 0.40 1.27 - - - - - suggested pad layout hx45 1.52 0.060 7.0 0.275 0.6 0 .024 1.27 0.050 4.0 0.155 mm inches
ZXGD3105N8 document number ds35101 rev. 1 ? 2 13 of 13 www.diodes.com november 2011 ? diodes incorporated a product line o f diodes incorporated ZXGD3105N8 important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries rese rve the right to make modifications, enhancements, improvements, corrections or ot her changes without further notice to this document and any product descri bed herein. diodes incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or user of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes inco rporated products for any unintended or una uthorized application, customers shall i ndemnify and hold diodes incorporated and its representativ es harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death a ssociated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical com ponents in life support devices or systems without the express written approval of the chief executive offi cer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when proper ly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support devic e or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifi cations of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-rel ated requirements concerning the ir products and any use of diodes incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or s ystems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporate d and its representatives against any damages arisi ng out of the use of diodes incorporated pr oducts in such safety-critical, life suppor t devices or systems. copyright ? 2011, diodes incorporated www.diodes.com

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