Linear Technology DC1749B Quick setup guide

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DEMO MANUAL DC1749B
Description
LT8610
42V, 2.5A Micropower Synchronous
Step-Down Regulator
Demonstration circuit 1749B is a 42V, 2.5A micropower
synchronous step-down regulator featuring the LT
®
8610.
The LT8610 is a compact, high efficiency, high speed
synchronous monolithic step-down switching regulator
that consumes only 2.5µA of quiescent current when
output is regulated at 5V. Top and bottom power switches,
compensation components and other necessary circuits
are inside of the LT8610 to minimize external components
and simplify design.
The SYNC pin on the demo board is grounded by default
for low ripple Burst Mode
®
operation. To synchronous to
an external clock, move JP1 to SYNC and apply the external
clock to the SYNC turret. Once JP1 is on SYNC position,
a DC voltage of higher than 2V or INTVCC can be applied L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
to the SYNC turret for pulse-skipping operation. Figure 1
shows the efficiency of the circuit at 12V input.
The demo board has an EMI filter installed. The EMI per-
formance of the board is shown on Figure 2. The limit in
Figure 2 is EN55022 class B, average. It shows the circuit
passes the test with a wide margin.
The LT8610 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 1749B.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1749B
Figure 1. LT8610 12VIN to 5VOUT Efficiency at 2MHz
Switching Frequency
Figure 2. LT8610 Demo Circuit EMI Performance,
Switching Frequency = 2MHz
LOAD CURRENT (A)
0
60
EFFICIENCY (%)
70
80
90
65
75
85
95
100
0.5 1
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21.5 2.5 START 150kHz
RES BW (CISPR) 9kHz
20
40
60
10
0
–10
30
50
70
80
MKR1 2.003MHz
21.69 dBµV
10 dB/DIV
dc1749b F02
VBW 62kHz STOP 30MHz
SWEEP 717ms (6637 PTS)

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DEMO MANUAL DC1749B
Quick start proceDure
Demonstration circuit 1749B is easy to set up to evalu-
ate the performance of the LT8610. Refer to Figure 3 and
Figure 4 for proper measurement equipment setup and
follow the procedure below:
1. With power off, connect the input power supply to VIN
and GND.
2. With power off, connect the load VOUT and GND.
3. Check JP1 setting
4. Turn on the power at the input.
5. Carefully evaluate other design parameters as needed.
Figure 3. Proper Measurement Equipment Setup
DC1749b F03
performance summary
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range 5.5 42 V
VOUT Output Voltage 4.8 5 5.2 V
IOUT Maximum Output Current 2.5 A
FSW Switching Frequency 1.85 2 2.15 MHz
EFE Efficiency at DC IOUT = 1A 92 %

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DEMO MANUAL DC1749B
Quick start proceDure
Figure 4. Measure Output Ripple
DC1749b F04

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DEMO MANUAL DC1749B
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C2 CAP, X7R, 4.7µF, 50V, 10%, 1206 MURATA, GRM31CR71H475KA12L
2 1 C4 CAP, X7R, 0.22µF, 16V, 10%, 0603 AVX, 0603YC224KAT2A
3 1 C5 CAP, C0G, 10pF, 25V, 10%, 0402 AVX, 04023A100KAT2A
4 1 C6 CAP, X7R, 47µF, 10V, 10%, 1210 MURATA, GRM32ER71A476KE20L
5 1 C7 CAP, X7R, 1µF, 25V, 10%, 0603 MURATA, GRM188R71E105KA12D
6 1 C8 CAP, X7R, 0.1µF, 16V, 10%, 0402 MURATA, GRM155R71C104KA88D
7 1 L1 IND, 2.2UH COILCRAFT, XAL5030-222MEC
8 1 R2 RES, CHIP, 18.2k, 1/10W, 1%, 0603 VISHAY, CRCW060318K2FKED
9 1 R3 RES, CHIP, 49.9k, 1/16W, 1%, 0402 VISHAY, CRCW040249K9FKED
10 2 R1, R4 RES, CHIP, 1M, 1/16W, 1%, 0402 VISHAY, CRCW04021M00FKED
11 1 R5 RES, CHIP, 243k, 1/16W, 1%, 0402 VISHAY, CRCW0402243KFKED
12 1 U1 IC, LT8610EMSE, MSE16 LINEAR TECHNOLOGY CORPORATION, LT8610EMSE
Additional Demo Board Circuit Components
1 1 C1 CAP, ALUM, 22µF, 63V SUN ELECT, 63CE22BS
2 2 C3, C10 CAP, X7R, 4.7µF, 50V, 10%, 1206 MURATA, GRM31CR71H475KA12L
3 1 C9 CAP, X7R, 4.7µF, 16V, 10%, 0805 MURATA, GRM21BR71C475K73L
4 1 C11 CAP, X7R, 1µF, 50V, 10%, 0805 TDK, C2012X7R1H105K
5 2 C12, C13 CAP, X7R, 0.1µF, 50V, 10%, 0402 TDK, C1005X7R1H104K
61 FB1 FERRITE BEAD, 0805 TDK, MPZ2012S221A
71 L2 IND 4.7UH VISHAY, IHLP2020BZ-ER4R7M01
8 0 R6 RES, OPT, 0402 OPT
Hardware: For Demo Board Only
1 9 E1 TO E9 TESTPOINT, TURRET, 0.094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 1 JP1 HEADER 1X3 079 SAMTEC, TMM-103-02-L-S
3 1 XJP1 SHUNT, 0.079" CENTER SAMTEC, 2SN-BK-G
4 4 MH1 TO MH4 STAND-OFF, NYLON 0.50" TALL KEYSTONE, 8833 (SNAP ON)

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DEMO MANUAL DC1749B
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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DEMO MANUAL DC1749B
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2012
LT 1113 REV A • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
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This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
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measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
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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
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