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A Product Line of Diodes Incorporated
ZXGD3101T8
Synchronous rectifier controller for flyback converters.
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
* * Turn-off propagation delay 15ns and turnoff time 20ns Suitable for Discontinuous Mode (DCM), Critical Conduction Mode (CrCM) and Continuous conduction mode (CCM) operation Compliant with Energy Star V2.0 and European Code of Conduct V3 Low component count Halogen free 5-15V VCC range
Applications
Flyback converters in: * * * * Adaptors LCD monitors Server PSU's Set top boxes
* * * *
Refer to documents; AN54, DN90, DN91 and DN94 available from the website
Pin out detail
Typical configuration
Transformer
N/C REF GATEL GATEH
1 2 3 4
8 7 6 5
DRAIN BIAS
R
RE F
R
B IA S
R EF
BIAS
Vcc
GND VCC
D R AIN
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 ZXGD3101T8TA Status Active Package SM8 Part Mark ZXGD3101 Reel size (inches) 7 Tape width (mm) 12 Quantity per reel 1000
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ZXGD3101T8
Absolute maximum ratings
Parameter Supply voltage1 Continuous Drain pin voltage1 GATEH and GATEL output Voltage1 Driver peak source current Driver peak sink current Reference current Bias voltage Bias current Power dissipation at TA =25C Operating junction temperature Storage temperature Symbol VCC VD VG ISOURCE ISINK IREF VBIAS IBIAS PD Tj Tstg Limit 15 -3 to180 -3 to VCC + 3 4 7 25 VCC 100 500 -40 to +150 -50 to +150 Unit V V V A A mA V mA mW C C
NOTES: 1. All voltages are relative to GND pin
Thermal resistance
Parameter Junction to ambient (*) Junction to lead () Symbol RJA RIA Value 250 54 Unit C/W C/W
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 Rating 4,000 400 Unit V V
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ZXGD3101T8
Electrical characteristics at TA = 25C;
VCC = 10V; RBIAS = 1.8k; RREF=3k Parameter Symbol Conditions Min. Typ. Max. Unit
Input and supply characteristics Operating current Gate Driver Turn-off Threshold Voltage(**) IOP VDRAIN -200m V VDRAIN 0V 3 8 mA
VT VG(off)
VG = 1V, (*) VDRAIN 0V, (*) VDRAIN = -60mV, ()
-45 5.0 7.0 8.4 9.2 9.3
-16 0.6 7.5 8.5 9 9.4 9.5 2.5 2.5 525
0 1 -
mV
GATE output voltage
(**)
VDRAIN = -80mV, () VG VDRAIN = -100mV, () VDRAIN -140mV, () VDRAIN -200mV, ()
V A A ns ns ns ns
GATEH peak source current GATEL peak sink current Turn on Propagation delay Turn off Propagation delay Gate rise time Gate fall time
NOTES:
ISOURCE ISINK td1 td2 tr tf
VGH = 1V VGL = 5V
CL = 2.2nF, () (a)
15 305 20
(**) GATEH connected to GATEL (*) RH = 100K, RL = 0/C () RL = 100K, RH = 0/C (a) (Refer to Fig 4; Test circuit and Fig 5; Timing diagram on page 11
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ZXGD3101T8
Schematic symbol and pin description
Vcc
+
H igh V o lt
G ate D rive C ontrol
+ -
com parator
GATEH
D river
H igh V o lt com parator
D R A IN
T urn-on/off C ontrol
GATEL
T hreshold V oltage C ontrol
REF
B IA S
GND
Pin No.
1 2
Symbol
NC REF
Description and function
No connection This pin can be connected to GND Reference This pin is connected to VCC via resistor, RREF. RREF should be selected to source ~3mA into this pin. See note 1 Gate turn off This pin sinks current, ISINK, from the synchronous MOSFET Gate. Gate turn on This pin sources current, ISOURCE, to the synchronous MOSFET Gate. Power Supply This is the supply pin. It is recommended to decouple this point to ground closely with a ceramic capacitor. Ground This is the ground reference point. Connect to the synchronous MOSFET Source terminal. Bias This pin is connected to VCC via resistor, RBIAS. RBIAS should be selected to source 1.6 times IREF into this pin. See note 1 Drain connection This pin connects directly to the synchronous MOSFET Drain terminal.
3 4 5
GATEL GATEH VCC
6
GND
7
BIAS
8
DRAIN
NOTES:
1. BIAS and REF pins should be assumed to be at GND+0.7V
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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
1
D rain current zero
6
M OSF ET Gate Voltage M OSF ET Gate C urrent
3 4
5 7
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ZXGD3101T8
Fig 1a: Continuous Conduction Mode (CCM)
Fig 1b: Critical Conduction Mode (CrCM)
Fig 1c: Discontinuous Conduction Mode (DCM) Figure 1. Typical waveforms Issue 4 - January 2009
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ZXGD3101T8
Typical characteristics
Turn-off offset voltage
Turn-off offset voltage
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ZXGD3101T8
Typical characteristics
Turn-off offset voltage
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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.
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ZXGD3101T8
+ Out R4 Vcc T ransform er + In C clam p R clam p RdC D R AIN ZX G D 3 1 0 1 GAT EL GAT EH GN D C1 D1 RRE F R EF R B IA S BIAS Vcc Q2
RdD D D clam p G S
GN D
- Out
Qpri PW M controller C C M/C rC M/D C M
S yn ch ro n o u s
FE T, Q syn
Optional diode, D f
- In
R snub
C snub
Figure 2 - Example connection for low side synchronous rectification
DA U X
VA U X
Rsnub Optional diode, D f G
C snub
S yn ch ro n o u s FE T, Q syn
+ Out
S
D
R4 Vcc T ransform er + In R EF C clam p R clam p RdC D R AIN ZX G D 3 1 0 1 GAT EL GAT EH GN D C1 D1 CA UX BIAS Vcc RRE F RB IA S Q2
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
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ZXGD3101T8
Vcc R REF 3 k REF BIAS R BIAS 1.8k Vcc RH
VD
DRAIN
ZXGD 3101
GATEL GATEH GND C1 1F X7R VG
C2 2200pF X7 R
RL
GND
Figure 4: Test circuit
Body Diode Conduction VD Zero voltage transition
20mV
-600mV
0V tf td1
90% -20 mV 10%
VG
tr
td2
NOTE: GATE H AND GATE L ARE CONNECTED
Figure 5: Timing diagram
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ZXGD3101T8
Package information - SM8 (Surface mounted, 8 pin package)
DIM Min. A A1 b c D E 0.02 0.24 6.3 3.3
Millimeters Max. 1.7 0.1 0.32 6.7 3.7 Typ. 0.7 Min. 0.0008 0.009 0.248 0.130
Inches Max. 0.067 0.004 0.013 0.264 0.145 Typ. 0.0275 -
DIM Min. e1 e2 He Lp 6.7 0.9 -
Millimeters Max. 7.3 15 Typ. 4.59 1.53 10 Min. 0.264 0.035 -
Inches Max. 0.287 15 Typ. 0.1807 0.0602 10
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
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Intentionally left blank
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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
3050 E. Hillcrest Drive Westlake Village, CA 91362-3154 Tel: (+1) 805 446 4800 Fax: (+1) 805 446 4850
Europe
Kustermann-Park Balanstrae 59, D-81541 Munchen Germany Tel: (+49) 894 549 490 Fax: (+49) 894 549 4949
Taiwan
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Shanghai
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Shenzhen
ANLIAN Plaza, #4018 Jintian Road Futian CBD, Shenzhen, China Tel: (+86) 755 882 849 88 Fax: (+86) 755 882 849 99
Korea
6 Floor, Changhwa B/D, 1005-5 Yeongtong-dong, Yeongtong-gu, Suwon-si, Gyeonggi-do, Korea 443-813 Tel: (+82) 312 731 884 Fax: (+82) 312 731 885
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