DC1412A - Demo Manual

DEMO CIRCUIT 1412A
QUICK START GUIDE
LT3758
LT3758EMSE
FLYBACK CONVERTER
DESCRIPTION
Demonstration
circuit
1412A
features
LT3758EMSE in a 300kHz Flyback converter
circuit, designed for 3.3V output from a 18V to
75V input.
The LT3758EMSE operates over an input range
of 5.5V to 100V, suitable for automotive, telecom and industrial applications. It also exhibits
low shutdown quiescent current of 1µA, making
them an ideal fit for battery-operated systems.
Thanks to a novel FBX pin architecture, the
LT3758EMSE can be connected directly to a
divider from either the positive output or the
negative output to ground. It also packs many
popular features such as soft-start, input under-
voltage lockout, adjustable frequency and synchronization in a small 10-lead MSOP package
or a 3mm × 3mm QFN package.
The LT3758EMSE datasheet gives a complete
description of the part, operation and application
information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1412A.
Design files for this circuit board are available. Call the LTC factory.
LT, LTC, LTM and
are registered trademarks of
Linear Technology Corporation. All other trademarks
are the property of their respective owners.
o
Table 1. Performance Summary for 300kHz Flyback Regulator ( TA = 25 C )
PARAMETER
CONDITION
Minimum Input Voltage
Maximum Input Voltage
Output Voltage VOUT
Maximum Output Current
Typical Switching Frequency
VALUE
18V
75V
3.3V +/-3%
3A
300kHz
QUICK START PROCEDURE
Demonstration circuit 1412A is easy to set up
to evaluate the performance of the
LT3758EMSE. Refer to Figure 1 for proper
measurement equipment setup and follow the
procedure below:
NOTE. When
measuring the input or output voltage ripple, care must be taken to avoid a long
ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the Vin or
Vout and GND terminals. See Figure 2 for
proper scope probe technique.
1. Place
JP1 on the ON position.
3. Turn
on the power at the input.
NOTE. Make sure that the input voltage does
not exceed the maximum input voltage.
4. Check
for the proper output voltages.
NOTE. If
there is no output, temporarily disconnect the load to make sure that the load
is not set too high.
Once the proper output voltages are established, adjust the loads within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
2. With
power off, connect the input power
supply to Vin and GND.
1
LT3758
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
2
GND
OFF
ON
E6
18V - 75V
JP1
RUN
3
2
1
OPT
R2
R7
1%
1%
105K
R8
VIN
8.66K
OPT
C3
100pF
C2
OPT
1%
36.5K
R5
0
R6
U1
4
2
9
1
3
RT
FB
SYNC
SENSE
GATE
I NTVCC
VIN
SHDN/U VLO
VC
SS
LT3758EMSE
C6 0.1uF
R16
100V
1uF
100V
1uF
CIN2
CIN1
5
6
7
8
OPT
C16
R21
6.81K 1%
R20
50V
4.7uF
C1
4700pF
C8
10K
R9
0
R4 0
D5
2
2
E7
SYNC
4
Si4848DY
Q2
BAS516
1
D2
BAV21W
1
220pF
C10
51.1 1%
R1
10K
R3
3
4
0.040
RCS1
5
6
7
8
1
2
3
7
8
5
6
R10 OPT
2200pF 250V
C9
2
1
BAS516
PS2801-1
U4
D3
PA1277NL
1
2
3
T1
0.47uF
C7
1uF
C4
499 1%
R11
C15 OPT
0
R18
1
3
2
3
2
1
OC
GND
VI N
FB
COM P
OPTO
LT4430ES6
U3
BAT54C
4
5
10nF
C5
VOUT
6.3V
100uF
1%
22.1K
R13
4.22K 1%
1%
100K
R14
0
E4
E1
270pF
C12
VOUT
Co3
R15
R12
OPT
6.3V
6.3V
C11
100uF
100uF
6
Co2
Co1
D4
VOUT
UPS840
D1
2
4
1
VIN
10
V IN
GND
11
VIN
3
E5
SEC. RTN
3.3V / 3A
+VOUT
LT3758
3
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