Rectifier Controller. LTC1698 Datasheet

LTC1698 Controller. Datasheet pdf. Equivalent

Part LTC1698
Description Isolated Secondary Synchronous Rectifier Controller
Feature U U LTC1698 Isolated Secondary Synchronous Rectifier Controller FEATURES s High Efficiency Over Wi.
Manufacture Linear
Datasheet
Download LTC1698 Datasheet



LTC1698
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



LTC1698
LTC1698
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VDD, PWRGD ....................................................... 13.2V
Input Voltage
MARGIN, VFB, OVPIN, ISNSGND, ISNS ... – 0.3V to 5.3V
SYNC ..................................................... – 14V to 14V
Output Voltage
VCOMP, ICOMP (Note 2) ......................... – 0.3V to 5.3V
Power Dissipation .............................................. 500mW
Operating Temperature Range
LTC1698E (Note 3) ............................ – 40°C to 85°C
LTC1698I ........................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
VDD 1
CG 2
PGND 3
GND 4
OPTODRV 5
VCOMP 6
MARGIN 7
VFB 8
16 FG
15 SYNC
14 VAUX
13 ICOMP
12 ISNS
11 ISNSGND
10 PWRGD
9 OVPIN
GN PACKAGE
S PACKAGE
16-LEAD PLASTIC SSOP 16-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 130°C/W (GN)
TJMAX = 125°C, θJA = 110°C/W (SO)
ORDER PART
NUMBER
LTC1698EGN
LTC1698ES
LTC1698IGN
LTC1698IS
GN PART MARKING
1698
1698I
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
VDD
VUVLO
IVDD
PARAMETER
Supply Voltage
Undervoltage Lockout
VDD Supply Current
MARGIN and Error Amplifier
VFB Feedback Voltage
CONDITIONS
VFB, OVPIN, VISNS, VISNSGND = 0V,
CFG = CCG = 1000pF, CVAUX = 0.1µF,
VSYNC = 0V
fSYNC = 100kHz (Note 5)
MARGIN = Open, VCOMP = 1V (Note 7)
IVFB
VMARGIN
RMARGIN
VFB
GERR
BWERR
VCLAMP
IVCOMP
OPTODRV
GOPTO
BWOPTO
VOPTOHIGH
IOPTOSC
Feedback Input Current
MARGIN Voltage
MARGIN Input Resistance
Feedback Voltage Adjustment
Error Amplifier Open-Loop DC Gain
Error Amplifier Unity-Gain Bandwidth
Error Amplifier Output Clamp Voltage
Error Amplifier Source Current
Error Amplifier Sink Current
Opto Driver DC Gain
Opto Driver Unity-Gain Bandwidth
Opto Driver Output High Voltage
Opto Driver Output Short-Circuit Current
VFB = 1.233V
MARGIN = Open
VMARGIN = 3.3V
VMARGIN = 0V
VCOMP = 0.8V to 1.2V, Load = 2k, 100pF
No Load (Note 6)
VFB = 0V
VFB = 0V
VFB = 5V, VCOMP = 1.233V
OVPIN, VISNS, VISNSGND = 0V
No Load (Note 6)
VFB, OVPIN, VISNSGND = 0V, VISNS = – 50mV,
IOPTODRV = –10mA
OVPIN, VISNSGND, VISNS = 0V, VFB = 1.233V
MIN TYP MAX
q6
8 12.6
4
q 1.8 4
5.0
1.223
q 1.215
q
q4
q –6
q 65
q
q3
1.233
1.233
0.05
1.65
16.5
5
–5
90
2
2
– 25
7
1.243
1.251
1
6
–4
– 10
q 4.75 5 5.25
1
q4
5
q – 50 – 25 – 10
UNITS
V
V
mA
mA
V
V
µA
V
k
%
%
dB
MHz
V
mA
mA
V/V
MHz
V
mA
1698f
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