A Product Line of Diodes Incorporated ZXGD3101T8 Synchronous rectifier controller for flyback converters. Zero Point Detector Driver ‘ZPDD’ Description The ZXGD3101 is intended to drive MOSFETS configured as ideal diode replacements. The device is comprised of a differential amplifier detector stage and high current driver. The detector monitors 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 reverse voltage drop and this is applied to the Gate via the driver. This action provides a rapid turn off as current decays. Features Applications • Turn-off propagation delay 15ns and turnoff time 20ns Flyback converters in: • Suitable for Discontinuous Mode (DCM), Critical Conduction Mode (CrCM) and Continuous mode(CCM) operation • Compliant with Energy Star V2.0 and European Code of Conduct V3 • Low component count • Halogen free • 5-15V VCC range • Adaptors • LCD monitors • Server PSU’s • Set top boxes Refer to documents; AN54, DN90 and DN91 available from the website Pin out detail Typical configuration Transformer N/C 1 8 DRAIN REF 2 7 BIAS GATEL 3 6 GND R R EF GATEH 4 5 R RE F BIAS D R AIN VCC B IA S Vcc ZX G D 3101 C1 GAT EL GAT EH GN D SM8 S yn ch ro n o u s R e ctifie r M O S FE T Ordering information Device Status Package Part Mark Reel size (inches) Tape width (mm) Quantity per reel ZXGD3101T8TA Active SM8 ZXGD3101 7 12 1000 Issue 3 - November 2008 © Diodes Incorporated 2008 1 www.zetex.com www.diodes.com ZXGD3101T8 Absolute maximum ratings Parameter Symbol Limit Unit Supply voltage1 VCC 15 V Continuous Drain pin voltage1 VD -3 to180 V GATEH and GATEL output Voltage1 VG -3 to VCC + 3 V ISOURCE 3 A Driver peak sink current ISINK 3 A Reference current IREF 25 mA Bias voltage VBIAS VCC V Bias current IBIAS 100 mA Power dissipation at TA =25°C PD 500 mW Operating junction temperature Tj -40 to +150 °C Tstg -50 to +150 °C Symbol Value Unit Junction to ambient (*) RθJA 250 °C/W Junction to lead (†) RθIA 54 °C/W Rating Unit 4,000 V 400 V Driver peak source current Storage temperature NOTES: 1. All voltages are relative to GND pin Thermal resistance Parameter NOTES: (*) Mounted on minimum 1oz copper on FR4 PCB in still air conditions (†) Output Drivers - Junction to solder point at end of the lead 5 and 6 ESD Rating Model Human body Machine Issue 3 - November 2008 © Diodes Incorporated 2008 2 www.zetex.com www.diodes.com ZXGD3101T8 Electrical characteristics at TA = 25°C; VCC = 10V; RBIAS = 1.8kΩ; RREF=3kΩ Parameter Symbol Conditions Min. Typ. Max. Unit mA Input and supply characteristics Operating current IOP VD ≤ -200m V - 3 - VD ≥ 0V - 8 - VD ≥ 0V (*) - 0 1.0 VD = -50mV (†) 2 6 - VD = -75mV(†) 6 8 - VD = -100mV(†) 8 9 - VD ≤ -200mV(†) 9.0 9.4 - Gate Driver GATE output voltage VG (GATEH connected to GATEL) GATEH peak source current GATEL peak sink current V ISOURCE VGH = 1V 2.5 - A ISINK VGL = 5V 2.5 - A Turn on Propagation delay td1 CL = 2.2nF(†) 525 ns Turn off Propagation delay td2 CL = 2.2nF(†) 15 ns Gate rise time tr CL = 2.2nF(†) 305 ns Gate fall time tf CL = 2.2nF(†) 20 ns NOTES: (*) RH = 1kΩ, RL = O/C (†) RH = O/C, RL = 1kΩ Refer to Fig 4; Test circuit and Fig 5; Timing diagram on page 11 Issue 3 - November 2008 © Diodes Incorporated 2008 3 www.zetex.com www.diodes.com ZXGD3101T8 Schematic symbol and pin description Vcc + H igh V o lt - G ate D rive C ontrol com parator GATEH D river + D R A IN - H igh V o lt com parator GATEL T urn-on/off C ontrol T hreshold V oltage C ontrol B IA S REF GND Pin No. Symbol Description and function 1 NC No connection This pin can be connected to GND 2 REF Reference This pin is connected to VCC via resistor, RREF. RREF should be selected to source ~3mA into this pin. (*) 3 GATEL Gate turn off This pin sinks current, ISINK, from the synchronous MOSFET Gate. 4 GATEH Gate turn on This pin sources current, ISOURCE, to the synchronous MOSFET Gate. 5 VCC Power Supply This is the supply pin. It is recommended to decouple this point to ground closely with a ceramic capacitor. 6 GND Ground This is the ground reference point. Connect to the synchronous MOSFET Source terminal. 7 BIAS Bias This pin is connected to VCC via resistor, RBIAS. RBIAS should be selected to source ~5mA into this pin.(*) 8 DRAIN Drain connection This pin connects directly to the synchronous MOSFET Drain terminal. NOTES: (*) BIAS and REF pins should be assumed to be at GND+0.7V. Issue 3 - November 2008 © Diodes Incorporated 2008 4 www.zetex.com www.diodes.com ZXGD3101T8 Operation Normal Operation The operation of the device is described step-by-step with reference to the timing diagram below. 1. The detector monitors the MOSFET Drain-Source voltage. 2. When, due to transformer action, the MOSFET body diode is forced to conduct there is approximately -0.6V on the Drain pin. 3. The detector outputs a positive voltage with respect to ground, this voltage is then fed to the MOSFET driver stage and current is sourced out of the GATEH pin. 4. The current out of the GATEH pin is sourced into the synchronous MOSFET Gate to turn the device on. 5. The GATEH output voltage is now proportional to the Drain-Source voltage drop across the MOSFET due to the current flowing through the MOSFET. 6. MOSFET conduction continues until the drain current reaches zero. 7. At zero current the detector output voltage is zero and the synchronous MOSFET Gate voltage is pulled low by the GATEL, turning the device off. Body D iode 2 C onduction M OSF ET D rain Voltage D rain current zero 1 6 M OSF ET Gate Voltage M OSF ET Gate C urrent Issue 3 - November 2008 © Diodes Incorporated 2008 5 3 7 4 5 www.zetex.com www.diodes.com ZXGD3101T8 Fig 1a: Continuous Conduction Mode (CCM) Fig 1b: Critical Conduction Mode (CrCM) Fig 1c: Discontinuous Conduction Mode (DCM) Figure 1. Typical waveforms Issue 3 - November 2008 © Diodes Incorporated 2008 6 www.zetex.com www.diodes.com ZXGD3101T8 Typical characteristics Turn-off offset voltage Issue 3 - November 2008 © Diodes Incorporated 2008 Turn-off offset voltage 7 www.zetex.com www.diodes.com ZXGD3101T8 Typical characteristics Turn-off offset voltage Issue 3 - November 2008 © Diodes Incorporated 2008 8 www.zetex.com www.diodes.com ZXGD3101T8 Typical characteristics Component selection It is advisable to decouple the ZXGD3101 closely to VCC and ground due to the possibility of high peak gate currents with C1 in Figure 2. The proper selection of external resistors RREF and RBIAS is important to the optimum device operation. Select a value for resistor RREF to give a reference current, IREF, of ~3mA. The value of RBIAS must then be 0.6 times the value of RREF to give a bias current, IBIAS, of 1.6 times IREF. This provides a recommended typical offset voltage of -20mV. External gate resistors are optional. They can be inserted to control the rise times which may help with EMI issues, power supply consumption issues or dissipation within the part. RREF = (VCC -0.7V)/ 0.003 RBIAS = (VCC -0.7V)/ 0.005 Layout considerations The Gate pins should be as close to the MOSFET Gate as possible. Also the ground return loop should be as short as possible. The decoupling capacitor should be close to the VCC and Ground pin, and should be a X7R type. For more detailed information refer to application note AN54. Issue 3 - November 2008 © Diodes Incorporated 2008 9 www.zetex.com www.diodes.com ZXGD3101T8 + Out R4 Vcc Q2 RRE F T ransform er + In R B IA S R EF BIAS Vcc C clam p R clam p C1 D R AIN ZX G D 3 1 0 1 RdC D1 GAT EL GAT EH GN D RdD G D S GN D D clam p - Out S yn ch ro n o u s Qpri FE T, Q syn PW M controller C C M/C rC M/D C M Optional diode, D f - In C snub R snub Figure 2 - Example connection for low side synchronous rectification DA U X VA U X C snub Rsnub Optional diode, D f S yn ch ro n o u s FE T, Q syn G + Out S D R4 Vcc Q2 RRE F T ransform er R B IA S + In R EF BIAS Vcc C clam p R clam p C1 D R AIN ZX G D 3 1 0 1 RdC D1 CA UX GAT EL GAT EH GN D RdD GN D D clam p - Out Qpri PW M controller C C M/C rC M/D C M - In Figure 3 - Example connection for high side synchronous rectification Issue 3 - November 2008 © Diodes Incorporated 2008 10 www.zetex.com www.diodes.com ZXGD3101T8 Vcc R REF R BIAS 3 kΩ 1.8kΩ REF VD BIAS DRAIN Vcc ZXGD 3101 RH GATEL GATEH GND C1 1μF X7R VG C2 2200pF X7 R RL GND Figure 4: Test circuit Body Diode Conduction Zero voltage transition VD -600mV 20mV 0V tf td1 90 % -20 mV VG 10 % td2 tr NOTE: GATE H AND GATE L ARE CONNECTED Figure 5: Timing diagram Issue 3 - November 2008 © Diodes Incorporated 2008 11 www.zetex.com www.diodes.com ZXGD3101T8 Package information - SM8 (Surface mounted, 8 pin package) DIM Millimeters Inches DIM Min. Max. Typ. Min. Max. Typ. A - 1.7 - - 0.067 - A1 0.02 0.1 - 0.0008 0.004 - e2 b - - 0.7 - - 0.0275 He c 0.24 0.32 - 0.009 0.013 - Lp D 6.3 6.7 - 0.248 0.264 - E 3.3 3.7 - 0.130 0.145 - Millimeters Inches Min. Max. Typ. Min. Max. Typ. - - 4.59 - - 0.1807 - - 1.53 - - 0.0602 6.7 7.3 - 0.264 0.287 - 0.9 - - 0.035 - - ␣ - 15° - - 15° -  - - 10° - - 10° e1 Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches Soldering footprint 2.8 0.110 6.8 0.268 4.6 0.181 mm inches 0.95 0.037 1.52 0.060 Issue 3 - November 2008 © Diodes Incorporated 2008 12 www.zetex.com www.diodes.com A Product Line of Diodes Incorporated Intentionally left blank Issue 3 - November 2008 © Diodes Incorporated 2008 13 www.zetex.com www.diodes.com ZXGD3101T8 Definitions Product change Diodes Incorporated reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or service. Customers are solely responsible for obtaining the latest relevant information before placing orders. Applications disclaimer The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for the user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is assumed by Diodes Inc. with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Diodes Inc. does not assume any legal responsibility or will not be held legally liable (whether in contract, tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract, opportunity or consequential loss in the use of these circuit applications, under any circumstances. Life support Diodes Zetex products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems 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 properly used in accordance with instructions for use provided in the labelling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Reproduction The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. Terms and Conditions All products are sold subjects to Diodes Inc. terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement. For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Diodes or Zetex sales office. Quality of product Diodes Zetex Semiconductors Limited is an ISO 9001 and TS16949 certified semiconductor manufacturer. To ensure quality of service and products we strongly advise the purchase of parts directly from Diodes Inc. or one of our regionally authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com or www.diodes.com Diodes Inc. does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales channels. ESD (Electrostatic discharge) Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices. The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time. Devices suspected of being affected should be replaced. Green compliance Diodes Inc. is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to reduce the use of hazardous substances and/or emissions. All Diodes Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance with WEEE and ELV directives. Product status key: “Preview” Future device intended for production at some point. Samples may be available “Active” Product status recommended for new designs “Last time buy (LTB)” Device will be discontinued and last time buy period and delivery is in effect “Not recommended for new designs” Device is still in production to support existing designs and production “Obsolete” Production has been discontinued Datasheet status key: “Draft version” This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. “Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance. However, changes to the test conditions and specifications may occur, at any time and without notice. “Issue” This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice. Sales offices The Americas Europe Taiwan Shanghai Shenzhen Korea 3050 E. 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