Datasheet LT8311 (Analog Devices) - 20
| Manufacturer | Analog Devices |
| Description | Synchronous Rectifier Controller with Opto-Coupler Driver for Forward Converters |
| Pages / Page | 48 / 20 — OPERATION. SYNC Mode Shutdown. PRIMARY-SIDE IC. LT8311 CONTROLS FG AND … |
| File Format / Size | PDF / 744 Kb |
| Document Language | English |
OPERATION. SYNC Mode Shutdown. PRIMARY-SIDE IC. LT8311 CONTROLS FG AND CG. CONTROLS TIMING. TIMING BASED ON SYNC INPUT. OF OUT AND
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LT8311
OPERATION SYNC Mode Shutdown
4. The CSP and CSN pins have tripped the LT8311’s in- In SYNC mode, the LT8311 will shut off both secondary- ternal current comparator during MCG’s on-time. The side MOSFETs, M current in MCG, IMCG, is sensed after a 400ns blank CG and MFG, if any of the following conditions are true: time has expired. This blank time starts at the turn-on edge of MCG. See the Applications Information section 1. VIN is less than its UVLO voltage for details on configuring the CSP and CSN pins in 2. INTV SYNC mode. CC outside its UVLO/OVLO limits 3. The TIMER pin has timed out (see the Applications Information section for details on programming the TIMER pin resistor). LOUT V T1 IN VOUT COUT • • MCG NP NS IMCG RESET
PRIMARY-SIDE IC
M1 MFG
LT8311 CONTROLS FG AND CG CONTROLS TIMING TIMING BASED ON SYNC INPUT OF OUT AND
FG CSN CG CSP
SIGNAL IN SYNC MODE SOUT SIGNALS
OUT LT8311 PRIMARY IC S T2 OUT SYNC • • CSYNC RSYNC M1 M1 TURN-ON TURN-ON EDGE EDGE OUT 0V 0V 0V SOUT 0V 0V 0V 1.2V 0V SYNC –1.2V MCG MCG TURN-ON TURN-ON EDGE EDGE CG 0V 0V 0V FG MFG MFG 0V TURN-ON 0V 0V TURN-ON 0V EDGE EDGE
TIME
8311 F07
Figure 7. In SYNC Mode, the Primary Side IC Sends SOUT Signals Through a Pulse Transformer to the LT8311’s SYNC Pin. SYNC < 1.2V Turns on MFG and Turns Off MCG. SYNC > 1.2V Turns On MCG and Turns Off MFG
8311f 20 For more information www.linear.com/LT8311 Document Outline Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation FUNDAMENTALS OF FORWARD CONVERTER OPERATION IN CCM LT8311 SYNCHRONOUS CONTROL SCHEMES PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL OPTO-COUPLER CONTROL Applications Information VIN BIAS SUPPLY INTVCC BIAS SUPPLY LT8311 OPTO CONTROL FUNDAMENTALS LT8311 SYNCHRONOUS CONTROL FUNDAMENTALS PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL Typical Applications Package Description Typical Application Related Parts
OPERATION SYNC Mode Shutdown
4. The CSP and CSN pins have tripped the LT8311’s in- In SYNC mode, the LT8311 will shut off both secondary- ternal current comparator during MCG’s on-time. The side MOSFETs, M current in MCG, IMCG, is sensed after a 400ns blank CG and MFG, if any of the following conditions are true: time has expired. This blank time starts at the turn-on edge of MCG. See the Applications Information section 1. VIN is less than its UVLO voltage for details on configuring the CSP and CSN pins in 2. INTV SYNC mode. CC outside its UVLO/OVLO limits 3. The TIMER pin has timed out (see the Applications Information section for details on programming the TIMER pin resistor). LOUT V T1 IN VOUT COUT • • MCG NP NS IMCG RESET
PRIMARY-SIDE IC
M1 MFG
LT8311 CONTROLS FG AND CG CONTROLS TIMING TIMING BASED ON SYNC INPUT OF OUT AND
FG CSN CG CSP
SIGNAL IN SYNC MODE SOUT SIGNALS
OUT LT8311 PRIMARY IC S T2 OUT SYNC • • CSYNC RSYNC M1 M1 TURN-ON TURN-ON EDGE EDGE OUT 0V 0V 0V SOUT 0V 0V 0V 1.2V 0V SYNC –1.2V MCG MCG TURN-ON TURN-ON EDGE EDGE CG 0V 0V 0V FG MFG MFG 0V TURN-ON 0V 0V TURN-ON 0V EDGE EDGE
TIME
8311 F07
Figure 7. In SYNC Mode, the Primary Side IC Sends SOUT Signals Through a Pulse Transformer to the LT8311’s SYNC Pin. SYNC < 1.2V Turns on MFG and Turns Off MCG. SYNC > 1.2V Turns On MCG and Turns Off MFG
8311f 20 For more information www.linear.com/LT8311 Document Outline Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation FUNDAMENTALS OF FORWARD CONVERTER OPERATION IN CCM LT8311 SYNCHRONOUS CONTROL SCHEMES PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL OPTO-COUPLER CONTROL Applications Information VIN BIAS SUPPLY INTVCC BIAS SUPPLY LT8311 OPTO CONTROL FUNDAMENTALS LT8311 SYNCHRONOUS CONTROL FUNDAMENTALS PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL Typical Applications Package Description Typical Application Related Parts