Secondary Side Synchronous Rectifier Controller

Transcription

1 Secondary Side Synchronous Rectifier ontroller Features High speed secondary synchronous rectifier High system efficiency from no load to full load Light load protection function DM topology 200 high voltage technology Ultra low startup and quiescent current cc ranges from 11.6 to 19.5 SOP-8 green (Halogen free) package Description GR8387 is the synchronous rectifier controller used in discontinuous conduction mode and quasi-resonant flyback converters. The I controls N-MOSFET to substitute Schottky diode. The D to S voltage difference is sensed to decide the polarity of the current and turn the power switch on/off in nearly of zero current transition. When light load the gate driver output can be disable to avoid long MOSFET turn on period. Applications ATX power supply NB adapter LD T SMPS Ordering and Marking Information SOP-8 ode A B G H I J Year ode A B Month Jan. Feb. Mar. Apr. Sep. Oct. Nov. Dec. Grenergy OPTO Inc. reserves the right to make changes to improve reliability or manufacture ability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders er opyright Grenergy OPTO, Inc. 1

2 Pin onfiguration Top iew 1 8 OUT OA 2 7 GND MOT 3 6 S EN 4 5 D Pin Descriptions Pin No. Name Function 1 Supply voltage 2 OA Offset voltage altering 3 MOT Minimum on time setting 4 EN Enable (Internal pull high) 5 D MOSFET drain voltage sensing 6 S MOSFET source voltage sensing 7 GND Ground 8 OUT Gate drive output Absolute Maximum Ratings, EN, S, OUT ~ 20 D (ontinued and pulsed) ~ 180 Operating junction temperature ~ 150 Storage temperature ~ 150 SOP-8 package thermal resistance /W Power dissipation (SOP-8, at ambient temperature = 85 ) mW ESD protection (Human body mode) K ESD protection (Machine Mode) Switching frequency KHz er opyright Grenergy OPTO, Inc. 2

3 Block Diagram er opyright Grenergy OPTO, Inc. 3

4 Electrical haracteristics ( = 15, Ta = 25, unless otherwise specified) Parameter onditions Symbol Min. Typ. Max. Unit SUPPLY SETION Supply voltage operating range turn on threshold ON turn off threshold ULO turn on/off hysteresis HYST Operating current LOAD =1nF, fsw = 500kHz I 9 13 ma LOAD = 10nF, fsw = 500kHz ma Quiescent current IQ ma Start-up current = ON I START µa Sleep current EN = 0, = 15 ISLEEP µa Enable voltage high ENHI 2.71 Enable voltage low ENLO 1.6 Enable pull-up resistance REN 1.5 MΩ OMPARATOR SETION OT = 0, S = Turn-off threshold OT floating, S = 0 TH m OT =, S = Turn-on threshold TH m Input bias current IIBIAS µa Input bias current D = 200 IIBIAS µa omparator input offset OFFSET 2 m Input M voltage range M NOISE REJET SETION RMOT = 5kΩ, = ns Minimum on time RMOT = 75kΩ, = 12 TONmin µs Reset threshold TH3 = 10 - GBD 2.5 TH3 = 20 - GBD 5.4 Hysteresis = 10 - GBD HYST3 40 m er opyright Grenergy OPTO, Inc. 4

5 Electrical haracteristics (ont.) GR8387 Parameter onditions Symbol Min. Typ. Max. Unit GATE DRIER SETION Gate low voltage IGATE = 200mA GLO Gate high voltage = (internally clamped) GTH Rise time LOAD = 1nF, = 12 tr1 20 ns LOAD = 10nF, = 12 tr2 270 ns Fall time LOAD = 1nF, = 12 tf1 8.5 ns LOAD = 10nF, = 12 tf2 42 ns Turn on propagation delay DS to GATE -100m overdrive tdon ns Turn off propagation delay DS to GATE -100m overdrive tdoff ns Pull up resistance IGATE = 1A - GBD rup 5 Ω Pull down resistance IGATE = -200mA rdown 1.7 Ω Output peak current (source) LOAD = 10nF - GBD IO source 1 A Output peak current (sink) LOAD = 10nF - GBD IO sink 4 A er opyright Grenergy OPTO, Inc. 5

6 Typical Application ircuit 1. Low side rectification 2. High side rectification er opyright Grenergy OPTO, Inc. 6

7 Application Information Overview GR8387, the secondary side driver I, emulates the operation of diode rectifier by driving a synchronous rectifier MOSFET. Using low R DS_ON N-MOSFET to substitute Schottky diode, the lower turn-on voltage will reduce conduction loss on rectifier. The efficiency of power converter will be boosted. Under-oltage Lockout (ULO) The GR8387 remains off until voltage exceeds turn-on threshold voltage (_ON). As the I is off, it takes as little current as 75uA. Once the rises above _ON, the I starts to work. It continues to operate until the voltage drops below turn-off threshold voltage (_OFF). makes OUT pin be pulled low and turns the MOSFET off. Minimum On time (MOT) and Turn Off Latch To avoid the mistrigger which is caused by noise as MOSFET is switching, minimum on time (MOT) function and turn off latch control have been built in GR8387. When OUT pin is pulled high, the minimum on time (MOT) which is setting by the resistor between MOT pin to ground keeps the MOSFET on. As OUT pin is pulled low, the MOSFET won t open again until the DS over reset threshold oltage (TH3), which means that the secondary side discharge has finished. Sleeping / Normal Mode Since the GR8387 cc pin voltage exceeds _ON, there are two modes available, sleeping mode and normal mode. The I will be in sleeping mode as EN pin is pulled low. In this mode, the I draws a very low quiescent supply current and MOSFET goes into off state. As EN pin is pulled high, the I will be in normal mode. In this mode, MOSFET starts to switch, and the I needs higher supply current to support function blocks working. OUT Pin Turn on/off Phase As secondary side rectifier is in conduction state, (Fig.1, T2) the rectifier current flows through the body diode of the MOSFET at first, which will generate a negative DS voltage on the MOSFET. The negative voltage will be below turn-on threshold voltage (TH2), and then the GR8387 OUT will be pulled high to drive the MOSFET turn on. The current will flow through the channel of the MOSFET and causes the DS voltage to drop down. When the MOSFET is turned on, it stays on until the rectifier current reduces to the level while DS exceeds the turn-off threshold voltage (TH1). This er opyright Grenergy OPTO, Inc. 7

8 Fig 1. Secondary Side Operation Fig 2. Normal Mode Operation (EN=H) Fig 3. Sleeping Mode Operation (EN=L) er opyright Grenergy OPTO, Inc. 8

9 Typical Performance haracteristics ) ( 10.6 N O Temperature ( ) ) ( O L U Temperature ( ) Fig 4. _ON vs. Temp. Fig 5. ULO vs. Temp ) ( T S Y H ) S u ( in m N O T RMOT = 5K RMOT = 75K Temperature ( ) Temperature ( ) Fig 6. HYST vs. Temp. Fig 7. TONmin vs. Temp. 0-5 OA = 0 OA = Floating OA = cc ) m ( 1 H T Temperature ( ) Fig 8. TH1 vs. Temp er opyright Grenergy OPTO, Inc. 9

10 Package Information SYMBOL MILLIMETERS SOP-8 INHES MIN. MAX. MIN. MAX. A A A b c D E E e 1.27 BS BS h L θ 0 o 8 o 0 o 8 o Note: 1. Followed from JEDE MS-012 AA. 2. Dimension D does not include mold flash, protrusions or gate burrs. Mold flash, protrusion or gate burrs shall not exceed 6 mil per side. 3. Dimension E1 does not include inter-lead flash or protrusions. Inter-lead flash and protrusions shall not exceed 10 mil per side er opyright Grenergy OPTO, Inc. 10

11 arrier Tape & Reel Dimensions SOP- 8 Application A H T1 d D W E1 F 330.0± MIN MIN MIN. 12.0± ± ±0.05 SOP-8 P0 P1 P2 D0 D1 T A0 B0 K0 4.0± ± ± MIN ± ± ±0.20 (mm) Devices Per Unit Application arrier Width over Tape Width Devices Per Reel SOP Grenergy OPTO, Inc. reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. ustomers should obtain the latest relevant information before placing orders and should verify that such information is current and complete er opyright Grenergy OPTO, Inc. 11