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zxgd3105n8 document number ds35101 rev. 3 - 2 1 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 synchronous mosfet co ntroller in so-8 description zxgd3105n8 synchronous controlle r is designed for driving a mosfet as an ideal rectifier. this is to replace a diode for increasing the power transfer efficiency. proportional gate drive control moni tors 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 controllers? output voltage is then proportional to the mosfet drain-source voltage and this is applied to the gate via the driver. this action minimizes body diode conduction whilst enabling a rapid mosfet turn-off as drain current decays to zero. applications flyback converters in: ? low voltage ac / dc adaptors ? set top box ? poe power devices resonant converters in: ? telecoms psu ? laptop adaptors ? computing power supplies - atx and server psu features ? proportional gate drive to minimize body diode conduction ? low standby power with quiescent supply current < 1ma ? 4.5v operation enables low voltage supply ? 25v v cc rating ? 100v drain voltage rating ? operation up to 500khz ? critical conduction mode (crcm) & continuous mode (ccm) ? compliant with eco-design directive ? totally lead-free & fully rohs compliant (notes 1 & 2) ? halogen and antimony free. ?green? device (note 3) ? qualified to aec-q101 standards for high reliability mechanical data ? case: so-8 ? case material: molded plasti c. ?green? molding compound. ? ul flammability classification rating 94v-0 ? moisture sensitivity: level 1 per j-std-020 ? terminals: finish ? matte tin plated leads, solderable per mil-std-202, method 208 ? solderable per mil-std-202, method 208 ? weight: 0.074 grams (approximate) ordering information (note 4) product marking reel size (inches) tape width (mm) quantity per reel zxgd3105n8tc zxgd3105 13 12 2500 notes: 1. no purposely added lead. fully eu directiv e 2002/95/ec (rohs) & 2011/6 5/eu (rohs 2) compliant. 2. see http://www.diodes.com for more info rmation about diodes incorpor ated?s definitions of halogen and antimony free,"green" and lead-free. 3. halogen and antimony free "green? products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm t otal br + cl) and <1000ppm antimony compounds. 4. 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. 3 - 2 2 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 functional block diagram pin number pin name description 1 v cc 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 v cc 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 v cc 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. 3 - 2 3 of 14 www.diodes.com march 2013 ? 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 25 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 5) p d 490 3.92 mw mw/c (note 6) 655 5.24 (note 7) 720 5.76 (note 8) 785 6.28 thermal resistance, junction to ambient (note 5) r ja 255 c/w (note 6) 191 (note 7) 173 (note 8) 159 thermal resistance, junction to lead (note 9) r jl 55 c/w ? thermal resistance, junction to case (note 10) r jc 45 c/w operating temperature range t j -40 to +150 c storage temperature range t stg -50 to +150 esd ratings (note 11) characteristic symbol value unit jedec class electrostatic discharge - human body model esd hbm 4,000 v 3a electrostatic discharge - machine model esd mm 200 v b notes: 5. for a device surface mounted on minimum recommended pad layout fr4 pcb with high coverage of single sided 1oz coppe r, in still air conditions; the device is measured when operating in a steady-state condition. 6. same as note (5), except pin 1 (v cc ) and pin 7 (gnd) are both connected to separate 5mm x 5mm 1oz copper heatsinks. 7. same as note (6), except both heatsinks are 10mm x 10mm. 8. same as note (6), except both heatsinks are 15mm x 15mm. 9. thermal resistance from junction to so lder-point at the end of each lead on pin 1 (v cc ) or pin 7 (gnd). 10. thermal resistance from junction to top of the case. 11. refer to jedec specification jesd22-a114 and jesd22-a115.
zxgd3105n8 document number ds35101 rev. 3 - 2 4 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 thermal derating curve 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 ? 1.2 ? a capacitive load: c l = 10nf gate peak sink current i sink ? 5 ? 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) ? 118 ? ns capacitive load: c l = 10nf rise and fall measured 10% to 90% gate rise time t r ? 77 ? turn-off propagation delay t d(fall) ? 14 ? gate fall time t f ? 26 ? 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
zxgd3105n8 document number ds35101 rev. 3 - 2 5 of 14 www.diodes.com march 2013 ? 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 40 45 130 140 150 160 170 180 190 200 210 220 230 0 2 4 6 8 10 12 14 16 18 20 22 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 resistor 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 drain sense voltage vs temperature v d drain voltage (mv) temperature (c) t off = t d2 + t f t on = t d1 + 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. 3 - 2 6 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 typical electrical characteristics (cont.) (@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 110100 10 100 0 200 400 600 -8 -6 -4 -2 0 2 4 110100 0 2 4 6 8 10 100 1000 10000 100000 1 10 100 v cc =10v r bias =18k ? r ref =9.1k ? c l =10nf r l =0r1 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 =0r1 v g v d switch off speed voltage (v) time (ns) v cc =10v r bias =18k ? r ref =9.1k ? r l =0r1 t on = t d1 + t r t off = t d2 + 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 =0r1 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 =0r1 -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 =0r1 supply current vs frequency frequency (hz) supply current (ma)
zxgd3105n8 document number ds35101 rev. 3 - 2 7 of 14 www.diodes.com march 2013 ? 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 yield significant power efficienc y improvement, whilst maintaining design simplicity and incurring minimal component count. figure 1 shows the typical configuration of zxgd3105 for sync hronous rectification in a low output vol tage flyback converter. a typical circuit configuration of synchronous rectification with zxgd3105 for use in resonant converter is shown in figure 2. two zxgd3105 together with two synchronous mosfets should be used on the se condary side of the center tapped transformer winding. figure 1 typical flyback application schematic figure 2 synchronous rectification in resonant converter threshold voltage and resistor setting the correct 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 v cc voltage. if the v cc pin is connected to the power converter?s output, the resistors should be selected based on the nominal conver ter?s output voltage. table 1 provides t he recommended resistor values for differ ent vcc voltages. supply, v cc (v) bias resistor, r bias (k ? ) reference resistor, r ref (k ? ) 5 9.6 4.3 10 18 9.1 12 24 11 15 30 15 table 1 recommended resistor values for different v cc voltages
zxgd3105n8 document number ds35101 rev. 3 - 2 8 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 application information (cont.) functional descriptions for flyback converter the operation of the device is described step-by-step wi th reference to the timing diagram in figure 3. 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 du e to the body diode forward voltage. 3. as the negative drain voltage crosses 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 driv er stage and current is sourced out of the gate pin. 4. the controller goes into proportional gate drive control ? t he gate output voltage is proportional to the mosfet on-resista nce- induced drain-source voltage. proportional gate drive ensures that mosfet conducts duri ng the majority of the conduction cycle to minimize power loss in the body diode. 5. as the drain current decays linearly toward zero, proporti onal gate drive control reduces the gate voltage so the mosfet ca n be turned off rapidly at zero current crossing. the gate voltage fa lls to 1v when the drain-source voltage crosses the detection threshold voltage to minimize reverse current flow. 6. at zero drain current, the controller gate output voltage is pulled low to v g(off) to ensure that the mosfet is off. figure 3 timing diagram for a critical conduction mode flyback converter
zxgd3105n8 document number ds35101 rev. 3 - 2 9 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 application information (cont.) functional descriptions fo r resonant converter the operation of the zxgd3105 in resonant converte r is described with reference to figure 4. 1. the detector stage monitors the mosfet drain-gnd voltage. 2. when, due to transformer action, the mosfet body diode is forced to conduct there is a negative voltage on the drain pin du e to the body diode forward voltage. 3. as the negative drain voltage crosses the threshold voltage v t , the detector stage outputs a positive voltage with respect to ground after the turn-on delay time t d(rise) . 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 control. t he gate voltage now varies according to the mosfet?s drain-gnd voltage. during this phase, the relationship of v g vs. v d is shown by the transfer characteristic curve in page xx of this datasheet. as the drain current decays linearly, the gate voltage reduces so the mosfet can be turned off rapidly at zero current crossing. proportional gate drive also ensures that gate voltage is supplied to the mosfet gate until the drain current is virtually zero. this eliminates any parasitic diode conducti on after the mosfet switches off. 5. the gate voltage falls to 1v when the drain-gnd voltage reaches v t . the mosfet is turned off pr ecisely when the sinusoidal current goes to zero, with little or no reverse current. threshold voltage v t is defined as the drain voltage v d level at which gate voltage v g is 1v (refer to electrical c haracteristic section in page 4). 6. at zero drain current, the gate voltage is pulled low to v g(off) to ensure that the mosfet is off. figure 4 timing diagram of synchronous rectif ication in the resonant converter
zxgd3105n8 document number ds35101 rev. 3 - 2 10 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 application information (cont.) besides that, proportional gate drive improv es the rectifier efficiency even at light to medium load condition by ensuring that the mosfets conduct during majority of the conduc tion cycle as shown in figure 5a. at reduced load condition, early terminati on of the gate drive voltage is likely for digital level gate drive due to the low cu rrent, which means that the threshold v t is breached. with the early termination of the gate drive voltage, mosfet turns off and the body diode conducts, see figure 5. this is shown by an increase in drain-gnd voltage for the remain ing time of the current waveform. with the current flowing thro ugh the body diode there will be an increase in power developed within the mosfet . the efficiency impact due to early termination of digital level gate driver increases with lower r ds(on) mosfet and/or higher operating frequency. (a) (b) figure 5 timing diagram of synchronous rectif ication in the resonant converter (a) proportional gate drive and (b) digital level gate drive
zxgd3105n8 document number ds35101 rev. 3 - 2 11 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 application information (cont.) gate driver the controller is provided with single channel high current gate drive output, capable of driving one or more n-channel power m osfets. the controller can operate from vcc of 4.5v to dr ive both standard mosfets and logic level mosfets. the gate pins should be as close to the mosf et?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 fa st discharge of the mosfet?s gate. figure 6 typical connection of the zxgd3105 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 increasing the value of resistor r ref and r bias . bias current, i bias (ma) ref current, i ref (ma) bias resistor, r bias (k ? ) ref resistor, r ref (k ? ) quiescent current, i q (ma) 0.25 0.61 39.2 15.4 0.86 0.35 0.81 28.0 11.5 1.16 0.46 0.99 21.5 9.3 1.45 0.50 1.00 19.6 8.9 1.50 0.55 1.13 17.8 8.1 1.68 0.80 1.66 12.1 5.6 2.46 table 2 quiescent current consumption for different resistor values at v cc = 10v i ref also controls the gate driv er 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 sour ce and 6a sink current. the gate current decreases if i ref and i bias are reduced. care must be taken in reducing the controller quiescent current so that sufficient drive current is still delivered to the mosf et particularly for high switching frequency application.
zxgd3105n8 document number ds35101 rev. 3 - 2 12 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 application information (cont.) layout guidelines when laying out the pcb, care must be tak en in decoupling the zxgd3105 closely to v cc and ground with 1 f low-esr, low-esl x7r type ceramic bypass capacitor. if the converter?s output voltage is higher than 20v, a 12v zener diode should be connected from the bias pin to gnd to clamp the gate voltage and protect the synchronous mo sfet. figure 7 shows the typical connection diagram. figure 7 zener voltage clamp arrangement gnd is the ground reference for the internal high voltage amplifie r as well as the current return for the gate driver. so the g round return loop should be as short as possible. sufficient pcb copper area s hould be allocated to the vcc and gnd pin for heat dissipation espe cially for high switching frequency application. any stray inductance involved by the load cu rrent may cause distortion of the drain- to-source voltage waveform, leading to prem ature turn-off of the synchronous mosfet. in order to avoid this issue, drain vo ltage sensing should be done as phys ically close to the drain ter minals as possible. the pcb track length between the controller drain pin and the mosfet?s terminal should be kept less than 10mm. mosfet packages with low internal wire bond inductance are preferred for high switching frequency power conver sion to minimize body diode condu ction. after the primary mosfet turns off, its drain voltage oscillates due to reverse recovery of the snubber diode. these high frequ ency oscillations are reflected across the transformer to t he drain terminal of the synchronous mosfet . the synchronous controller senses the dra in voltage ringing, causing its gate output voltage to oscillate. the sy nchronous mosfet cannot be fully enhanced until the drain voltage stabilizes. in order to prevent this issue, the oscill ations on the primary mosfet can be damped with either a series resistor rd to the sn ubber diode or an r-c network across the diode (refer figure 8). both methods reduc e the oscillations by softeni ng the snubber diode?s reverse re covery characteristic. figure 8 primary side snubber network to reduce drain voltage oscillations
zxgd3105n8 document number ds35101 rev. 3 - 2 13 of 14 www.diodes.com march 2013 ? diodes incorporated a product line o f diodes incorporated zxgd3105n8 package outline dimensions please see ap02002 at http://www.diodes.com /datasheets/ap02002.pdf for latest version. suggested pad layout please see ap02001 at http://www.diodes.com/dat asheets/ap02001.pdf for the latest version. so-8 dim min max a - 1.75 a1 0.10 0.20 a2 1.30 1.50 a3 0.15 0.25 b 0.3 0.5 d 4.85 4.95 e 5.90 6.10 e1 3.85 3.95 e 1.27 typ h - 0.35 l 0.62 0.82 ?? 0 ? 8 ? all dimensions in mm dimensions value (in mm) x 0.60 y 1.55 c1 5.4 c2 1.27 x c1 c2 y gauge plane seating plane detail ?a? detail ?a? e e1 h l d e b a2 a1 a 45 7 ~ 9 a3 0.254
zxgd3105n8 document number ds35101 rev. 3 - 2 14 of 14 www.diodes.com march 2013 ? 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, enhanc ements, 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 ari sing out of the application or use of this document or any product described he rein; 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 a nd all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability w hatsoever 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. this document is written in english but may be translated into multiple languages for reference. only the english version of t his document is the final and determinative format released by diodes incorporated. 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 ? 2013, diodes incorporated www.diodes.com

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