FUNDAMENTALS OF FORWARD CONVERTER OPERATION IN CCM ..................................................................... 13
LT8311 SYNCHRONOUS CONTROL SCHEMES..................................................................................................... 17
PREACTIVE MODE SYNCHRONOUS CONTROL .................................................................................................... 17
SYNC MODE SYNCHRONOUS CONTROL ............................................................................................................. 19
OPTO-COUPLER CONTROL .................................................................................................................................. 21
Applications Information .......................................................................................................25
Related Parts .....................................................................................................................48
8311f
2
For more information
www.linear.com/LT8311
LT8311
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
CSW
FSW
FG
INTV
CC
V
IN
PMODE
OPTO
1
3
5
6
7
8
9
20 CSP
18 CSN
16 CG
15 SYNC
14 SS
13
PGOOD
12 TIMER
11 FB
CSW, FSW, CSP ....................................... –0.3V to 150V
SYNC ........................................................... –12V to 12V
V
IN
,
PGOOD
................................................ –0.3V to 30V
INTV
CC
,
PMODE
......................................... –0.3V to 18V
FB, SS, COMP ........................................... –0.3V to 2.5V
TIMER ....................................................... –0.3V to 1.5V
CSN........................................................... –0.3V to 0.4V
OPTO, TIMER Short-Circuit
Current Duration .................................... Infinite (Note 5)
Operating Junction Temperature Range
LT8311E (Notes 2, 3) ......................... –40°C to 125°C
LT8311I (Notes 2, 3) .......................... –40°C to 125°C
LT8311H (Notes 2, 3) ......................... –40°C to 150°C
LT8311MP (Notes 2, 3) ...................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10sec).................... 300°C
21
GND
COMP 10
FE PACKAGE
20-LEAD PLASTIC TSSOP
θ
JA
= 38°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT8311EFE#PBF
LT8311IFE#PBF
LT8311HFE#PBF
LT8311MPFE#PBF
TAPE AND REEL
LT8311EFE#TRPBF
LT8311IFE#TRPBF
LT8311HFE#TRPBF
LT8311MPFE#TRPBF
PART MARKING*
LT8311FE
LT8311FE
LT8311FE
LT8311FE
PACKAGE DESCRIPTION
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
8311f
For more information
www.linear.com/LT8311
3
LT8311
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 12V, V
INTVCC
= 8V,
PMODE
= 5V, C
CG
= C
FG
= 100pF, unless
otherwise noted. (Note 2)
PARAMETER
Supply
V
IN
Operating Range
V
IN
UVLO
Quiescent Current
Error Amplifier
Feedback Reference Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
Feedback Pin Bias Current
Error Amplifier Transconductance
Error Amplifier Voltage Gain
Error Amplifier Output Swing High
Error Amplifier Output Swing Low
Power Good
Power NOT Good (Outside This Window) % Relative to FB Ref Voltage
Power Good (Inside This Window)
Power Good Indicator Wait Time
Power Good Leakage
Power Good Output Low Voltage
Soft-Start (SS)
SS Wake-Up Slew Current
SS Wake-Up Offset Voltage
SS Charge Current
SS Pull-Down Amplifier Offset Voltage
Current Exists Upon Part Wake Up, Shuts Off After SS Wake Up
Offset Voltage Is Satisfied (Note 6)
V
FB
– V
SS
, Upon Part Wake Up SS Is Slewed Up to an Offset
Voltage Below FB by SS Wake-Up Slew Current
SS = 0V, FB = 0.6V (Note 9)
V
SS
– V
FB
, Pull-Down Amplifier Prevents SS from Rising Beyond
This Offset Voltage Above FB When the FB Pin Voltage Is Below
50% of the FB Reference Voltage
SS = 1.5V, FB = 0.6V (Note 7)
1.8
1.3V ≤ COMP (Note 5)
(Note 5)
(Note 5)
l
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
3.7
50
TYP
MAX
30
UNITS
V
V
mV
mA
V
%
%
nA
µmhos
dB
V
IN
Rising
Hysteresis
Not Switching
V
IN
= 12V
3.7V ≤ V
IN
≤ 30V, % of FB Ref Voltage
1.3V ≤ COMP ≤ 1.8V, % of FB Ref Voltage
Current Out of FB pin
1.3V ≤ COMP ≤ 1.8V
1.3V ≤ COMP ≤ 1.8V
FB = 1V
FB = 1.5V
l
3.6
100
4.5
3.7
150
5.5
1.245
0.1
0.1
200
l
1.209
1.227
0.015
0.05
120
370
65
1.9
0.75
±4
2.3
1
±10
±7
175
2.8
1.25
±16
V
V
%
%
µs
% Relative to FB Ref Voltage
Minimum Time That FB Must Stay within Power Good Window
Before
PGOOD
Pin Goes Low
PGOOD
= 30V
Current into
PGOOD
Pin = 1mA
l
±1
0.2
1
16
9
10
100
11
0.3
µA
V
mA
mV
µA
mV
SS Pull-Down Amplifier Maximum
Sink Current
SS High Clamp Voltage
Opto Driver
COMP Buffer Input Offset Voltage
Opto-Driver Reference Voltage
Opto-Driver DC Gain
13
2
0.9
1
–7
mA
V
V
V
V/ V
8311f
4
For more information
www.linear.com/LT8311
LT8311
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
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