A Product Line of Diodes Incorporated ZXGD3105N8 SYNCHRONOUS MOSFET CONTROLLER IN SO-8 Description Features 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 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 voltage and this is applied to the Gate via the driver. This action provides 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 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 Plastic. “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) SO-8 Vcc GATE DNC GND BIAS DNC DRAIN REF Top View Pin-Out Ordering Information (Note 3) Product ZXGD3105N8TC Notes: Marking ZXGD 3105 Reel size (inches) 13 Tape width (mm) 12 Quantity per reel 2500 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 3105 YY WW ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 ZXGD 3105 YY WW 1 of 13 www.diodes.com = Product Type Marking Code, Line 1 = Product Type Marking Code, Line 2 = Year (ex: 11 = 2011) = Week (01 - 53) November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Functional Block Diagram Pin # Pin Name 1 Vcc Power supply This supply pin should be closely decoupled to ground with a ceramic capacitor. 2 DNC Do not connect Leave pin floating. 3 BIAS Bias Connect this pin to Vcc via RBIAS resistor. Select RBIAS to source 0.54mA into this pin. Refer to Table 1 and 2, in Application Information section. 4 DRAIN 5 REF Reference Connect this pin to Vcc via RREF resistor. Select RREF 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 ISINK and ISOURCE current to the synchronous MOSFET gate. Pin Function and Description Drain sense Connect directly to the synchronous MOSFET drain terminal. ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 2 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Maximum Ratings @TA = 25°C unless otherwise specified Characteristic Supply voltage, relative to GND Drain pin voltage Gate output voltage Gate Driver peak source current Gate Driver peak sink current Reference voltage Reference current Bias voltage Bias current Symbol VCC VD VG ISOURCE ISINK VREF IREF VBIAS IBIAS Value 15 -3 to 100 -3 to VCC + 3 4 9 VCC 25 VCC 100 Unit V V V A A V mA V mA Value 490 Unit Thermal Characteristics @TA = 25°C unless otherwise specified Characteristic Symbol (Note 4) Power Dissipation Linear derating factor 3.92 655 (Note 5) PD (Note 6) Thermal Resistance, Junction to Ambient Thermal Resistance, Junction to Lead Operating Temperature Range Storage Temperature Range Notes: 720 mW mW/°C 5.76 785 (Note 7) (Note 4) (Note 5) (Note 6) (Note 7) (Note 8) 5.24 6.28 RθJA RθJL TJ TSTG 255 191 173 159 135 -40 to +150 -50 to +150 °C/W °C/W °C 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 (VCC) 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 (VCC) and pin 7 (GND). ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 3 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Max Power Dissipation (W) Thermal Derating Curve 0.8 15mm x 15mm 0.7 10mm x 10mm 0.6 0.5 5mm x 5mm 0.4 Minimum Layout 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 140 160 Junction Temperature (°C) Derating Curve ESD Rating Characteristic Value ESD for Human Body Model 4000 ESD for Machine Model 200 ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 4 of 13 www.diodes.com Unit V November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Electrical Characteristics @TA = 25°C unless otherwise specified VCC = 10V; RBIAS = 18kΩ (IBIAS = 0.54mA); RREF = 9.1kΩ (IREF = 1.02mA) Characteristic Input Supply Quiescent current Gate Driver Gate peak source current Gate peak sink current Detector under DC condition Turn-off Threshold Voltage Gate output voltage Switching Performance Turn-on propagation delay Gate rise time Turn-off propagation delay Gate fall time ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 Symbol Min Typ Max Unit IQ - 1.56 - mA ISOURCE ISINK - 2 7 - A VT VG(off) -20 5.0 8.0 -10 0.2 7.8 9.4 0 0.6 - 70 175 15 20 - VG td(rise) tr td(fall) tf 5 of 13 www.diodes.com mV V ns Test Condition VDRAIN ≥ 0mV Capacitive load: CL = 20nF VG = 1V VDRAIN ≥ 1V VDRAIN = -50mV VDRAIN = -100mV Capacitive load only Rise and fall measured 10% to 90% Refer to application test circuit below November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Typical Electrical Characteristics @TA = 25°C unless otherwise specified 14 VG Gate Voltage (V) VCC = 15V 12 VCC = 12V VCC = 10V 10 8 6 VCC = 5V 4 2 Capacitive load only 0 -100 -80 -60 -40 -20 VG Gate Voltage (V) 6 VCC = 5V 4 2 Capacitive load and 50kΩ pull down 0 -100 -80 -60 -40 -20 Transfer Characteristic Transfer Characteristic T A = 25°C T A = 125°C 6 VCC = 10V RBIAS=18kΩ RREF=9.1kΩ 50kΩ pull down -80 -60 -40 -20 0 VD Drain Voltage (mV) 0 0 VCC = 10V -5 RBIAS=18kΩ RREF=9.1kΩ -10 VG = 1V 50kΩ pull down -15 -20 -25 -30 -50 0 50 100 150 Temperature (°C) Turn-off Threshold Voltage vs Temperature Transfer Characteristic 180 230 220 210 200 190 180 170 160 150 140 130 Ton = td(rise) + tr VCC = 10V RBIAS=18kΩ RREF=9.1kΩ Toff = td(fall) + tf CL=10nF 35 30 -50 Supply Current (mA) Switching Time (ns) 8 VD Drain Voltage (mV) 8 0 -100 VCC = 10V VD Drain Voltage (mV) T A = -40°C 2 VCC = 12V 10 0 10 4 VCC = 15V 12 Turn-off Threshold Voltage (mV) VG Gate Voltage (V) 14 160 RBIAS=18kΩ 140 RREF=9.1kΩ VCC = 15V f=500kHz 120 100 VCC = 12V VCC = 10V 80 60 40 20 VCC = 5V 0 -25 0 25 50 75 100 125 150 0 Temperature (°C) Switching vs Temperature ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 2 4 6 8 10 12 14 16 18 20 22 Capacitance (nF) Supply Current vs Capacitive Load 6 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Continued - Typical Electrical Characteristics @TA = 25°C unless otherwise specified 10 10 VG 8 VCC=10V VD 6 Voltage (V) Voltage (V) 8 RBIAS=18kΩ RREF=9.1kΩ 4 CL=10nF RL=0.1Ω 2 0 VCC=10V 6 RBIAS=18kΩ VG VD RREF=9.1kΩ 4 CL=10nF RL=0.1Ω 2 0 -2 -100 -2 0 100 200 300 -200 -100 Time (ns) 0 100 200 300 Time (ns) Switch On Speed Switch Off Speed Time (ns) T on = td(rise) + tr 100 Toff = td(fall) + tf VCC=10V RBIAS=18kΩ RREF=9.1kΩ RL=0.1Ω Gate Drive Current (A) 4 10 0 -2 VCC=10V -4 RBIAS=18kΩ -6 CL=10nF RREF=9.1kΩ ISINK RL=0.1Ω -8 10 1 ISOURCE 2 0 100 200 400 600 Time (ns) Capacitance (nF) Gate Drive Current Switching vs Capacitive Load VCC=10V VCC=10V Supply Current (mA) Peak Drive Current (A) 10 RBIAS=18kΩ 8 RREF=9.1kΩ -ISINK RL=0.1Ω 6 4 ISOURCE 2 RBIAS=18kΩ 100 RREF=9.1kΩ RL=0.1Ω 10 100 CL=3.3nF 1 10 100 1000 10000 100000 Frequency (Hz) Gate Current vs Capacitive Load Document Number DS35101 Rev. 1 – 2 CL=10nF 10 Capacitance (nF) ZXGD3105N8 CL=33nF CL=1nF 0 1 CL=100nF 7 of 13 www.diodes.com Supply Current vs Frequency November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Application Information The purpose of the ZXGD3105 is to drive a MOSFET as a low-VF Schottky diode replacement in isolated AC/DC converter. When combined with a low RDS(ON) MOSFET, the controller can yield significant power efficiency improvement, whilst maintaining design simplicity and incurring minimal component count. Figure 1 shows the typical configuration of ZXGD3105 for synchronous rectification in a low output voltage Flyback converter. Figure 1 - Typical Flyback application schematic Threshold voltage and resistor setting Proper selection of external resistors RREF and RBIAS is important for optimum device operation. RREF and RBIAS supply fixed current into the IREF and IBIAS pin of the controller. IREF and IBIAS combines to set the turn-off threshold voltage level, VT. In order to set VT to -10mV, the recommended IREF and IBIAS are 1.02mA and 0.54mA respectively. The values for RREF and RBIAS are selected based on the Vcc voltage. If the Vcc pin is connected to the power converter’s output, the resistors should be selected based on the nominal converter’s output voltage. Table 1 provides the recommended resistor values for different Vcc voltages. Supply, Vcc Bias Resistor, RBIAS Reference Resistor, RREF 5 V 10 V 12 V 15 V 9.6 kΩ 18 kΩ 24 kΩ 30 kΩ 4.3 kΩ 9.1 kΩ 11 kΩ 15 kΩ Table 1 – Recommended resistor values for different Vcc voltages ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 8 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Functional descriptions The operation of the device is described 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 crosses the turn-off Threshold voltage VT, the detector stage outputs a positive voltage with respect to ground after the turn-on delay time td(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 control — 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 current crossing. The GATE voltage falls 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 VG(off) to ensure that the MOSFET is off. MOSFET Drain Voltage VD 1 VT Body Diode Conduction 2 3 90% MOSFET Gate Voltage 4 5 VG 90% 10% 6 10% VG(off) tf tr td(fall) td(rise) MOSFET Drain Current ID 0A Figure 2 - Timing diagram for a critical conduction mode Flyback converter ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 9 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Gate driver The controller is provided with single channel high current gate drive output, capable of driving one or more Nchannel 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 ZXGD3105 to the synchronous MOSFET Quiescent current consumption The quiescent current consumption of the controller is the sum of IREF and IBIAS. For an application that requires ultralow standby power consumption, IREF and IBIAS can be further reduced by increasing the value of resistor RREF and RBIAS. Bias Current Ref Current IBIAS 0.25mA 0.35mA 0.46mA 0.50mA 0.55mA 0.80mA IREF 0.61mA 0.81mA 0.99mA 1.00mA 1.13mA 1.66mA Bias Resistor RBIAS Ref Resistor RREF Quiescent Current IQ 39.2KΩ 28.0KΩ 21.5KΩ 19.6KΩ 17.8KΩ 12.1KΩ 15.4KΩ 11.5KΩ 9.3KΩ 8.9KΩ 8.1KΩ 5.6KΩ 0.86mA 1.16mA 1.45mA 1.50mA 1.68mA 2.46mA Table 2 – Quiescent current consumption for different resistor values at Vcc=10V IREF also controls the gate driver peak sink current whilst IBIAS controls the peak source current. At the default current value of IREF and IBIAS of 1.02mA and 0.54mA, the gate driver is able to provide 2A source and 6A sink current. The gate current decreases if IREF and IBIAS are reduced. Care must be taken in reducing the controller quiescent current so that sufficient drive current is still delivered to the MOSFET particularly for high switching frequency application. ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 10 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 Layout guidelines When laying out the PCB, care must be taken in decoupling the ZXGD3105 closely to VCC and ground with 1μF lowESR, low-ESL X7R type ceramic bypass capacitor. If the converter’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 amplifier 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 cause 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. MOSFET 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 transformer to the drain terminal of the synchronous MOSFET. The synchronous controller senses the drain voltage ringing, causing its gate output voltage to oscillate. The synchronous MOSFET cannot be fully enhanced until the drain voltage stabilizes. In order to prevent this issue, the oscillations 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 reduce drain voltage oscillations ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 11 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of Diodes Incorporated ZXGD3105N8 h x 45° Package Outline Dimensions DIM Inches Millimeters DIM Inches Min. Millimeters Max. Max. Min. Max. A 0.053 0.069 1.35 1.75 e 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 θ 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 - - - - - 0.050 BSC Min. Max. Min. 1.27 BSC Suggested Pad Layout 1.52 0.060 7.0 0.275 4.0 0.155 0.6 0.024 1.27 0.050 mm inches ZXGD3105N8 Document Number DS35101 Rev. 1 – 2 12 of 13 www.diodes.com November 2011 © Diodes Incorporated A Product Line of 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). 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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 labeling 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. 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