Linear Technology LTC7103 Quick setup guide

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DEMO MANUAL
DC2317A
DESCRIPTION
LTC7103
105V, 2.3A Low EMI Synchronous
Step-Down Regulator
Demonstration circuit 2317A is a 100V monolithic DC/
DC step-down regulator featuring the LT C
®
7103. The
demo board is designed for a 5V/2.3A output from a 5V
to 100V input at 400kHz switching frequency. The wide
input range makes it suitable for automotive, industrial,
medical instrument, and telecom applications. This buck
regulator has a peak efficiency of 93.5% at 12VIN, 88.3%
at 48VIN and 81.5% at 100VIN (see Figure 3).
The LTC7103 is a compact, high efficiency synchronous
monolithic step-down switching regulator with fast cur-
rent programming. The power switches, compensation
network and other necessary circuits are inside of the
LTC7103 to minimize external components and simplify
design. The LTC7103 has wide operating range from 4.4V
to 105V. A 40ns minimum on-time, together with 100%
maximum duty cycle allow practical use at any output volt-
age between 1V and VIN. The switching frequency can be
programmed either via an oscillator resistor or an external
clock over a 200kHz to 2MHz range. Additional features
include a fast and accurate output current programming
and monitoring, and ultralow EMI/EMC emissions.
The demo board has an EMI filter installed. The EMI
performance of the board (with EMI filter) is shown in
Figure2. The figure shows that the circuit passes the
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Analog Devices, Inc. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
CISPR 25 radiated emission test with a wide margin. To
achieve EMI/EMC performance as shown in Figure 2, the
input EMI filter is required and the input voltage should
be applied at +VIN_EMI turret pin.
The demo board provides current monitor and output
clock signal to interface with an external application cir-
cuit. User selectable mode selection (JP1) is provided and
Burst Mode
®
operation position is selected by default.
Burst Mode operation increases light load efficiency while
pulse-skipping mode allows constant-frequency operation
to a lighter load. This demo board allows phase-locked
loop (PLL) synchronization to an external clock by select-
ing SYNC mode on JP1 and by providing a clock signal
on CLKIN turret.
The LTC7103 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this demo manual
for DC2317A. The LTC7103 is assembled in the 36 (26)
lead QFN package. Proper board layout is essential for
maximum thermal and electrical performance. See the
data sheet sections for details.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2317A
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range 5 100 V
VOUT Output Voltage 5 V
IOUT Output Current Range, Continuous Free Air 0 2.3 A
fSW Switching (Clock) Frequency 400 kHz
VOUTP-P Output Ripple VIN = 100V, VOUT = 5V, IOUT = 2.3A (20MHz BW) 50 mVP-P
POUT/PIN Efficiency VIN = 12V, IOUT = 1A
VIN = 48V, IOUT = 1A
92.6
88.1
%
%
Approximate Size Component Area x Top Component Height 1.0 × 0.7 × 0.3 Inches

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QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup
Refer to Figure 1 for proper measurement equipment
setup and follow the procedure below.
Note: When measuring the output voltage ripple, care
must be taken to avoid a long ground lead on the oscil-
loscope probe. Measure the output voltage ripple by
touching the probe tip and ground ring directly across
the last output capacitor as shown in Figure 1.
1. Place SW1 to ON position.
2. With power off, connect the input power supply to
+VIN_EMI and GND. If the EMI/EMC performance is
not important, the input EMI filter can be bypassed by
connecting the input power supply to +VIN and GND.
3. With power off, connect loads from +VOUT to GND.
4. Turn on the power at the input. Make sure that the input
voltage does not exceeds 100V.
5. Check for the proper output voltage using a voltmeter.
Output voltage should be within 5.0V ± 0.1V.
Note: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
6. Once the proper output voltage is established, adjust
the load within the operating ranges and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
7. An external clock can be added to the CLKIN terminal
when SYNC mode is used (JP1 on the SYNC position).
See the data sheet Frequency Selection and Phase-
Locked Loop section for details.
+
–
+–
LOAD
IOUT
VOUT
IIN
VIN
+
–
+
–
+
–
+–
POWER
SUPPLY
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Figure 2. EMI Performance in CISPR 25 Radiated Emission Test (48VIN from +VIN_EMI Turret Pin, 5VOUT/2A, fSW = 400kHz)
VERTICAL POLARIZATION
CLASS 5 PEAK LIMIT
LTC7103
FREQUENCY (MHz)
0
100
200
300
400
500
600
700
800
900
1000
0
10
20
30
40
50
AMPLITUDE (dBµV/m)
dc2017a F02a
HORIZONTAL POLARIZATION
CLASS 5 PEAK LIMIT
LTC7103
FREQUENCY (MHz)
0
100
200
300
400
500
600
700
800
900
1000
0
10
20
30
40
50
AMPLITUDE (dBµV/m)
dc2017a F02b
QUICK START PROCEDURE

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Figure 3. Efficiency at Various Input Voltages (Conditions: Burst Mode Operation)
QUICK START PROCEDURE
Figure 4. Efficiency at Various Input Voltages (Conditions: Pulse-Skipping Mode)

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QUICK START PROCEDURE
Figure 5. Output Ripple at 100VIN, 5VOUT and 2.3AOUT (50mV, 500ns/DIV, 20MHz Bandwidth)
Figure 6. Transient Response Waveform at 48VIN, 5VOUT and 1.1AOUT to 2.3AOUT to 1.1AOUT (1A, 200mV, 50μs/DIV, 20MHz Bandwidth)

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Figure 7. Thermal Plots (without Forced Air)
Conditions: 12VIN, 5VOUT at 2.3AOUT Conditions: 24VIN, 5VOUT at 2.3AOUT
Conditions: 48VIN, 5VOUT at 2.3AOUT Conditions: 100VIN, 5VOUT at 2.3AOUT
QUICK START PROCEDURE

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Figure 8. Board Photo
QUICK START PROCEDURE

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PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 3 C1, C13, C16 CAP, X7R 4.7µF, 100V, 20% 1210 MURATA, GRM32ER72A475KE14
2 1 C2 CAP, X7R, 0.1µF, 100V, 10%, 0805 MURATA, GCM21BR72A104KA37L
3 1 C3 CAP, X7R, 0.1µF, 25V, 10%, 0603 MURATA, GRM188R71E104KA01D
4 1 C5 CAP, X6S, 100µF, 6.3V, 20%, 1210 MURATA, GRM32EC80J107ME20L
5 1 C7 CAP, X7R, 1µF, 16V, 10%, 0805 AVX, 0805YC105KAT2A
6 1 C14 CAP, 33µF, 100V, 200mA PANASONIC, EEEFK2A330P
7 1 C18 CAP, X7R, 1µF, 50V, 10%, 0603 YAGEO.,CC0603KRX7R9BB105
8 1 C20 CAP, X7R, 0.22µF, 100V, 10%, 0805 TAIYO YUDEN,HMK212B7224KGHT
9 1 L1 IND, 15µH COILCRAFT, XAL6060-153ME
9 0 L1 (ALTERNATE) IND, 15µH WURTH, 74439346150
10 1 R1 RES, 10MEG, 1%, 0805 VISHAY, CRCW080510M0FKEA
11 5 R2, R5, R6, R14, R24 RES, 0Ω, JUMPER 0603 VISHAY, CRCW06030000Z0EA
12 1 R8 RES, 1k, 1%, 0603 VISHAY, CRCW06031K00FKEA
13 1 R13 RES, 100k, 1%, 0603 VISHAY, CRCW0603100KFKEA
14 1 R15 RES, 8.87k, 1%, 0603 VISHAY, CRCW06038K87FKEA
15 1 R16 RES, 17.8k, 1%, 0603 NIC, NRC06F1782TRF
16 1 U1 LTC7103EUHE32, QFN 5mm × 6mm LINEAR TECH.CORP. LTC7103EUHE#PBF
Additional Demo Board Circuit Components
18 0 C4, C6, C8–C12, C15, C17, C19, C21 CAP, OPTIONAL OPTIONAL
19 0 L2 IND, OPTIONAL OPTIONAL
20 0 R3, R4, R7, R12, R17, R21–R23, R25–R27 RES, OPTIONAL OPTIONAL
Hardware for Demo Board Only
22 11 E1–E4, E6–E12 TESTPOINT, TURRET 0.095" MILLMAX, 2501-2-00-80-00-00-07-0
23 2 FB1, FB2 FERRITE BEAD, 120Ω AT 100MHz, 1206 MURATA., BLM31PG121SN1
24 1 FB3 RES, 0Ω, SHUNT,1206 VISHAY, CRCW12060000Z0EA
25 1 JP1 HEADER, 4-PIN DBL ROW 2mm SAMTEC, TMM-104-02-L-D
26 1 XJP1 SHUNT SAMTEC, 2SN-BK-G
27 1 SW1 SWITCHE, SUB MINIATURE SLIDE SWITCHE C&K.,JS202011CQN
28 4 (STAND-OFFS) STAND-OFF, NYLON 0.5" TALL KEYSTONE, 8833 (SNAP ON)
29 1 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 2317A
30 2 STENCILS TOP AND BOTTOM STENCIL DC2317A

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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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM

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 LINEAR TECHNOLOGY CORPORATION 2017
LT 0617 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
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. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
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Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application
engineer.
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