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DESCRIPTION
Demonstration circuit 1803A is a monolithic high voltage
isolated fl yback converter featuring the LT
circuit is designed for a 5V isolated output from an input
voltage range of 36V to 75V. The maximum output current
is 500mA. V
can be lower if output current is less than
IN
500mA. The circuit doesn't require an opto-isolator due to
the output voltage being sensed directly from the primary
side transformer winding. A third winding is used to bias
the LT3512 for highest effi ciency.
The fl yback converter requires a minimum loading to
maintain good regulation. A Zener diode is placed between
+
–
V
and V
to clamp output voltage to ~7.5V if mini-
OUT
OUT
mum load requirement is not met. Depending on the input
voltage and the output regulation requirement, a 20mA to
30mA minimum load is usually suffi cient.
The demo circuit uses a diode-Zener clamp to limit the
peak spike voltage due to transformer leakage inductance.
A diode-Zener clamp is more effi cient than a RCD clamp.
The LT3512 operates in boundary mode and also provides
output voltage temperature compensation.
PERFORMANCE SUMMARY
PARAMETER
Minimum Input Supply Voltage
Maximum Input Supply Voltage
Output Voltage
Output Voltage Tolerance
Switching Frequency
Maximum Output Current
Effi ciency
DEMO MANUAL DC1803A
The LT3512 data sheet gives a complete description of
®
3512. The demo
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 1803A.
Design fi les for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
(T
= 25°C)
A
CONDITIONS
I
= 500mA
OUT
I
= 500mA
OUT
V
= 36V, I
= 500mA
IN
OUT
V
= 75V, I
= 500mA
IN
OUT
V
= 36V, I
= 500mA
IN
OUT
LT3512: Monolithic
High Voltage Isolated
Flyback Converter
90
80
70
60
50
40
30
20
10
0
50 100 150
200
250 300
350
LOAD CURRENT (mA)
Figure 1. DC1803A Effi ciency
VALUE
36
75
±5
160
240
500
84
V
= 5V
OUT
T
= 25°C
A
V
= 36V
IN
V
= 75V
IN
400 450
500
DC1803A F01
UNITS
V
V
5
V
%
kHz
kHz
mA
%
dc1803af
1
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Summary of Contents for Linear Technology LT3512
- Page 1 L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear side transformer winding. A third winding is used to bias Technology Corporation. All other trademarks are the property of their respective owners.
-
Page 2: Quick Start Procedure
Demonstration circuit 1803A is easy to set up to evalu- 2. Connect a load of 500mA or less to V and V ate the performance of the LT3512. Refer to Figure 2 for terminals (not GND). proper measurement equipment setup and to follow the 3. -
Page 3: Schematic Diagram
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. - Page 4 Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods.
- Page 5 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Analog Devices Inc. DC1803A...
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