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LTC1698 の電気的特性と機能

LTC1698のメーカーはLinearです、この部品の機能は「Isolated Secondary Synchronous Rectifier Controller」です。


製品の詳細 ( Datasheet PDF )

部品番号 LTC1698
部品説明 Isolated Secondary Synchronous Rectifier Controller
メーカ Linear
ロゴ Linear ロゴ 




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LTC1698 Datasheet, LTC1698 PDF,ピン配置, 機能
LTC1698
Isolated Secondary
Synchronous Rectifier Controller
FEATURES
s High Efficiency Over Wide Load Current Range
s ±0.8% Output Voltage Accuracy
s Dual N-Channel MOSFET Synchronous Drivers
s Pulse Transformer Synchronization
s Optocoupler Feedback Driver
s Programmable Current Limit Protection
s ±5% Margin Output Voltage Adjustment
s Adjustable Overvoltage Fault Protection
s Power Good Flag
s Auxiliary 3.3V Logic Supply
s Available in 16-Lead SSOP and SO Packages
U
APPLICATIO S
s 48V Input Isolated DC/DC Converters
s Isolated Telecommunication Power Systems
s Distributed Power Step-Down Converters
s Industrial Control Systems
s Automotive and Heavy Equipment
DESCRIPTIO
The LTC®1698 is a precision secondary-side forward
converter controller that synchronously drives external
N-channel MOSFETs. It is designed for use with the
LT®3781 primary-side synchronous forward converter
controller to create a completely isolated power supply.
The LT3781 synchronizes the LTC1698 through a small
pulse transformer and the LTC1698 drives a feedback
optocoupler to close the feedback loop. Output accuracy
of ±0.8% and high efficiency over a wide range of load
currents are obtained.
The LTC1698 provides accurate secondary-side current
limit using an external current sense resistor. The input
voltage at the MARGIN pin provides ±5% output voltage
adjustment. A power good flag and overvoltage input are
provided to ensure proper power supply conditions. An
auxiliary 3.3V logic supply is included that supplies up to
10mA of output current.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
36V to 72V
Q1
L1
VDD BIAS +
+
COUT
R2
R1
VOUT
D1
T1
Q2 D2
RPRISEN
TG BG
CSG
SG
T2
Q4
Q3
RSECSEN
CSYNC
RSYNC
1 10
2 VDD PWRGD 8
CG VFB
16
FG LTC1698
12
ISNS
6
VCOMP
RC
CC
CFB
11
ISNSGND
13 RCILM
ICOMP
CCILM
15
SYNC
9
OVPIN
7
MARGIN
VMARGIN
R5
R4
LT3781
+ REF
VFB
VC
RF
CF
RE
ISOLATION
BOUNDARY
RK 5
14 VAUX
OPTODRV
VAUX
3.3V
CK PGND GND O.1µF 10mA
34
1681 F01
PLEASE REFER TO FIGURE 12 IN THE TYPICAL APPLICATIONS
SECTION FOR THE COMPLETE 3.3V/15A APPLICATION SCHEMATIC
Figure 1. Simplified 2-Transistor Isolated Forward Converter
1698f
1

1 Page





LTC1698 pdf, ピン配列
LTC1698
ELECTRICAL CHARACTERISTICS The q indicates specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VDD = 8V, unless otherwise noted. (Note 4)
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX
UNITS
VAUX
VAUX Auxiliary Supply Voltage
Current Limit Amplifier
CVAUX = 0.1µF, ILOAD = 0mA to 10mA, VDD = 7V to 12.6V q 3.135 3.320 3.465
V
IISNSGND
IISNS
VILIMTH
IICOMP
ISNSGND Input Current
ISNS Input Current
Current Limit Threshold
(VISNS – VISNSGND)
ICOMP Source Current
ICOMP Sink Current
VISNSGND = 0V
VISNS = 0V
VICOMP = 2.5V, VISNSGND = 0V
VISNSGND = 0V, VISNS = – 0.3V, VICOMP = 2.5V (Note 8)
VISNSGND = 0V, VISNS = 0.3V, VICOMP = 2.5V (Note 8)
q
q
– 27.0
q – 27.5
– 280
q – 370
120
q 80
0.05
0.05
– 25
– 25
– 200
– 200
200
200
1
1
– 23.0
– 22.5
– 120
– 80
280
370
µA
µA
mV
mV
µA
µA
µA
µA
gmILIM Current Limit Amplifier
Transconductance
VISNSGND = 0V, VICOMP = 2.5V, IICOMP = ±10µA
q 2.2 3.5
5 millimho
GICOMP Current Limit Amplifier
Open-Loop DC Gain
VICOMP = 2.5V, No Load
q 48
60
dB
PWRGD and OVP Comparators
VPWRGD Percent Below VFB
IPWRGD Power Good Sink Current
VOL
VOVPREF
IOVPIN
tPWRGD
Power Good Output Low Voltage
OVPIN Threshold
OVPIN Input Bias Current
Power Good Response Time
Power Bad Response Time
tOVP Overvoltage Response Time
SYNC and Drivers
VFB , MARGIN = Open (Note 9)
VFB = 2V
VFB = 0V
IPWRGD = 3mA, VFB = 0V
VFB = VISNS = VISNSGND = 0V, OVPIN (Note 9)
VOVPIN = 1.233V
VFB
VFB
VOVPIN , COPTODRV = 0.1µF
q –9
q
q 10
q
q 1.18
q
q1
q 0.5
q
–6
1.233
0.1
2
1
5
–3
10
0.4
1.28
1
5
2.5
20
%
µA
mA
V
V
µA
ms
ms
µs
VPT
VNT
ISYNC
fSYNC
td
tSYNC
tr, tf
SYNC Input Positive Threshold
SYNC Input Negative Threshold
SYNC Input Current
SYNC Frequency Range
SYNC Input to Driver Output Delay
Minimum SYNC Pulse Width
Driver Rise and Fall Time
VSYNC = ±10V
CFG = CCG = 1000pF, VSYNC = ±5V
CFG = CCG = 1000pF, fSYNC = 100kHz, VSYNC = ±5V
fSYNC = 100kHz, VSYNC = ±10V (Note 6)
CFG = CCG = 1000pF, fSYNC = 100kHz, VSYNC = ±5V,
10% to 90%
q1
1.6 2.2
q – 2.2 –1.6 –1
q 1 50
q 50
400
q 40 90
q 75
q 10 40
V
V
µA
kHz
ns
ns
ns
tDDIS Driver Disable Time-Out
CFG = CCG = 1000pF, fSYNC = 100kHz, VSYNC = ±5V
Measured from CG (Note 10)
q 10 15 20
µs
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired. All voltages refer to GND.
Note 2: The LTC1698 incorporates a 5V linear regulator to power internal
circuitry. Driving these pins above 5.3V may cause excessive current flow.
Guaranteed by design and not subject to test.
Note 3: The LTC1698E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. For guaranteed performance to
specifications over the –40°C to 85°C range, the LTC1698I is available.
Note 4: All currents into device pins are positive; all currents out of the
device pins are negative. All voltages are referenced to ground unless
otherwise specified. For applications with VDD < 7V, refer to the Typical
Performance Characteristics.
Note 5: Supply current in active operation is dominated by the current
needed to charge and discharge the external FET gates. This will vary with
the LTC1698 operating frequency, supply voltage and the external FETs
used.
Note 6: This parameter is guaranteed by correlation and is not tested.
Note 7: VFB is tested in an op amp feedback loop which servos VFB to the
internal bandgap voltage.
Note 8: The current comparator output current varies linearly with
temperature.
Note 9: The PWRGD and OVP comparators incorporate 10mV of
hysteresis.
Note 10: The driver disable time-out is proportional to the SYNC period
within the frequency synchronization range.
1698f
3


3Pages


LTC1698 電子部品, 半導体
LTC1698
TYPICAL PERFOR A CE CHARACTERISTICS
IVDD vs SYNC Frequency
50
VDD = 8V
45 TA = 25°C
CFG = CCG = 4700pF
40
CFG = CCG = 3300pF
35
CFG = CCG = 2200pF
30
25
20
15
10
CFG = CCG = 1000pF
5
0
50 100 150 200 250 300 350 400 450 500
fSYNC (kHz)
1698 G19
Opto Driver Short-Circuit Current
vs VDD
0
TA = 25°C
VOPTODRV = 1.233V
–10
–20
–30
–40
–50
5 6 7 8 9 10 11 12 13 14
VDD (V)
1698 G17
Driver Rise, Fall and Propagation
Delay vs Driver Load
90
VDD = 8V
80 TA = 25°C
70 CG, FG tPLH
60
50
tf tr
40 CG, FG tPHL
30
20
10
0
0 2000 4000 6000 8000 10000
DRIVER LOAD (pF)
1698 G25
SYNC Positive Threshold
vs Temperature
2.25
VDD = 8V
2.00
SYNC Positive Threshold
vs VDD
2.20
TA = 25°C
1.96
1.75 1.72
1.50 1.48
1.25 1.24
1.00
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1698 G20
1.00
5 6 7 8 9 10 11 12 13 14
VDD (V)
1698 G21
IVDD vs VDD
20
TA = 25°C
18 fSYNC = 100kHz
CFG = CCG = 4700pF
16
CFG = CCG = 3300pF
14
12
10
8
6
CFG = CCG = 2200pF
4
CFG = CCG = 1000pF
2
0
5 6 7 8 9 10 11 12 13 14
VDD (V)
1698 G18
Undervoltage Lockout Threshold
vs Temperature
5
4
3
2
1
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1698 G24
SYNC Input to Driver Output Delay
vs Temperature
90
VDD = 8V
80 CCG = CFG = 1000pF
fSYNC = 100kHz
70
60
50 CG, FG tPLH
40 CG, FG tPHL
30
20
10
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1698 G26
Driver Disable Time-Out vs SYNC
Frequency
30 VDD = 8V
TA = 25°C
25
2.2
2.0
20
tDISS × fSYNC
1.8
15 1.6
10 1.4
tDISS
5 1.2
0 1.0
50 100 150 200 250 300 350 400 450 500
fSYNC (kHz)
1698 G27
1698f
6

6 Page



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