DC662A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 662
36V 600MA 500KHZ SOT-23 STEP-DOWN REGULATOR
LT1933
DESCRIPTION
Demonstration circuit 662 is a monolithic step-down
DC/DC switching converter featuring the LT®1933.
The board is optimized for 3.3V output at up to
500mA load current for a steady state input voltage
range of 4.5V to 36V. With its wide input voltage
range, high current internal power switch, low dropout operation, 500kHz switching frequency and tiny
SOT-23 package, the LT1933 is a very versatile and
powerful IC for DC/DC converters that require extremely compact space, high efficiency and high input
voltage.
The LT1933 500kHz switching frequency allows all of
the components to be small, surface mount devices.
The current-mode control topology creates fast transient response and good loop stability with a minimum number of external components. The low resistance internal power switch (0.37V VCEsat) achieves
high efficiencies of up to 84%. The shutdown pin can
be used to program undervoltage lockout or place the
part in micropower shutdown, reducing supply current to less than 2µA by driving the pin low (without
R1 installed). The internal soft start function reduces
input current surge during start-up.
The LT1933 datasheet gives a complete description of
the part, operation and applications information. The
datasheet must be read in conjunction with this Quick
Start Guide for demonstration circuit 662. In particular, the datasheet section on ‘Thermal Calculations’ is
important for estimating whether a given application’s
combination of input voltage, load current, ambient
temperature and frequency will cause the LT1933 to
exceed it’s absolute maximum rated junction temperature. The LT1933 is assembled in a small low
profile SOT-23 ThinSOT package. Proper board layout
is essential for maximum thermal performance. See
the datasheet section ‘Layout Considerations’.
Design files for this circuit board are available. Call
the LTC factory.
LT is a trademark of Linear Technology Corporation
QUICK START PROCEDURE
Demonstration circuit 662 is easy to set up to evaluate the performance of the LT1933. Refer to Figure 1
for proper measurement equipment setup and follow
the procedure below:
NOTE: Make
sure that the input voltage does not ex-
ceed 36V.
NOTE: The
shutdown function is optional and its terminal can be left floating (disconnected) if shutdown
is not being used.
not hot-plug the input voltage terminal VIN.
The absolute maximum voltage on VIN is 36V and
hot-plugging a power supply through wire leads to
the demonstration circuit can cause the voltage on
the extremely low-ESR ceramic input capacitor to ring
to twice its DC value. In order to protect the IC, a
higher ESR Aluminum Electrolytic capacitor, C4, is
placed at the input terminals. This may protect
against some, but not all, input transients due to hotplugging with a power supply. See Application Note
88 for more details.
NOTE: Connect
the power supply (with power off),
load, and meters as shown in Figure 1.
1.
NOTE: Do
After all connections are made, turn on input power
and verify that the output voltage is 3.3V.
NOTE: If
the output voltage is too low, temporarily
disconnect the load to make sure that the load is
not set too high.
2.
Once the proper output voltages are established,
adjust the load within the operating range and ob-
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 662
36V 600MA 500KHZ SOT-23 STEP-DOWN REGULATOR
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 662
36V 600MA 500KHZ SOT-23 STEP-DOWN REGULATOR
3
5
4
3
2
1
D
D
C
5
VIN
4
SHDN
BOOST 1
SW
GND
FB
2
3
6
C
B
B
A
A
5
4
3
2
1
Bill Of Material
Demo Bd. #662A
Linear Technology Corporation
LT1933ES6
Item Qty Reference
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1
1
1
1
1
1
0
1
1
1
1
5
1
4
4
1
1
C1
C2
C3
C4
D1
D2
D3
L1
R1
R2
R3
TP1,TP2,TP3,TP4,TP5
U1
Part Description
Cap., X7R 0.1uF 16V 10%
Cap., X5R 22uF 6.3V 10%
Cap., X7R 2.2uF 50V 10%
Cap., Alum 10uF 50V 20%
Schottky Rectifier, Powermite
Schottky Diode, 1A/45V
(OPT)
Inductor, 22uH
Res., Chip 100K 0.06W 5%
Res., Chip 16.5K 0.06W 1%
Res., Chip 10.0K 0.06W 1%
Turret, Testpoint
I.C., Switching Reg.
SCREW #4-40 1/4"
STANDOFF #4-40x1/4"
PRINTED CIRCUIT BOARD
STENCIL (TOP)
Page 1 - of - 1
Manufacture / Part #
AVX 0603YC104KAT1A
Taiyo Yuden JMK316BJ226KL-T
TDK C3225X7R1H225KT
OSCON 50CV10BJ
ON Semiconductor MBRM140T3
Diodes Inc. SDM10K45-7
(OPT)
Sumida CDRH4D28-220NC
AAC CR05-104JM
AAC CR05-1652FM
AAC CR05-1002FM
Mill Max 2501-2
Linear Tech. Corp. LT1933ES6
ANY
MICRO PLASTICS 14HTSP101
DEMO CIRCUIT #662A
STENCIL #662A
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