DEMO MANUAL DC1520A
LT3690:
36V/4A µPower Synchronous
Buck Regulator
DESCRIPTION
The current mode control scheme creates fast transient
response and good loop stability. The driver of the internal HS switch is boosted to a voltage that is higher than
the VIN to ensure saturation of the switch. The LT3690’s
integrated boost diode and switches reduce the part
count. Meanwhile, the internal synchronous power switch
increases efficiency and eliminates the need for an external
Schottky catch diode. The EN pin can be used to set the
part in micro power shutdown mode, reducing the supply
current to less than 1μA.
must be read in conjunction with this demo manual for
demo circuit 1520A. The LT3690 is assembled in a 26-lead
plastic UFE package with two thermally enhanced pads for
SW and GND. Proper board layout is essential for both
proper operation and maximum thermal performance. See
the data sheet section PCB Layout and High Temperature
Considerations.
Efficiency vs Load Current
100
VOUT = 3.3V
f = 450kHz
90
EFFICIENCY (%)
Demonstration circuit 1520A is a 36V, 4A synchronous
Buck Regulator with 70μA Quiescent Current featuring
the LT3690. The demo board is designed for 3.3V output
from a 4.5V to 36V input with transient up to 60V. The wide
input range of the LT3690 allows a variety of input sources,
such as automotive batteries and industrial supplies. The
switching frequency can be programmed either via oscillator resistor or external clock over a 170kHz to 1.5MHz
range. When the circuit is synchronized to an external
clock connected to the SYNC terminal, the RT resistor
(R5) should be chosen to set the LT3690 internal switching
frequency at least 20% below the lowest synchronization
input frequency. The modes of operation (fixed frequency
and Burst Mode®) are jumper selectable. The Burst Mode
operation increases the efficiency at light loads while fixed
frequency mode maintains a constant switching frequency
regardless of the load current.
80
70
60
50
VIN = 12V
VIN = 24V
VIN = 36V
0
0.5
1
1.5 2 2.5 3
LOAD CURRENT (A)
3.5
4
dc1520 F01
Figure 1. DC1520A Efficiency
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, μModule, Linear Technology, the Linear logo and Burst Mode are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
The LT3690 datasheet gives a complete description of the
part, operation and application information. The data sheet
PERFORMANCE SUMMARY
PARAMETER
(TA = 25°C)
CONDITIONS
MIN
TYP
MAX
UNITS
Minimum Input Supply Voltage
4.5
V
Maximum Input Supply Voltage
36
V
Output Voltage VOUT
3.3
V
Maximum Output Current
Switching Frequency
4
RT = 45.3k
450
A
kHz
dc1520af
1
DEMO MANUAL DC1520A
QUICK START PROCEDURE
Demonstration circuit 1520A is easy to set up and evaluate the performance of the LT3690. Refer to Figure 2 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.
1. Place jumpers in the following positions:
JP1: EN
JP2: Burst Mode
2. With power off, connect the input power supply to VIN
and GND.
3. Connect a load of 4A or less to VOUT and GND terminals.
4. Turn on the power at the input.
NOTE. Make sure that the input voltage does not
exceed 36V.
5. Check for the proper output voltage (3.3V).
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 and input 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 SYNC terminal
when SYNC function is used (JP2 open). Please make
sure that the SYNC frequency is at least 20% higher
than the set switching frequency. See the data sheet
section Synchronization.
dc1520af
2
DEMO MANUAL DC1520A
QUICK START PROCEDURE
+
+
–
+
–
–
LOAD
+
+
–
+
–
–
Figure 2. Proper Measurement Equipment Setup
Figure 3. Measuring Input or Output Ripple
dc1520af
3
DEMO MANUAL DC1520A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
1
C2
Capacitor, X5R, 10μF, 50V, 20%, 1210
Taiyo Yuden, UMK325BJ106MM-T
2
1
C3
Capacitor, X5R, 47μF, 6.3V, 20%, 1210
Taiyo Yuden, JMK325BJ476MM-T
3
1
C4
Capacitor, X5R, 0.68μF, 10V, 10%, 0603
Taiyo Yuden, LMK107BJ684KA-T
4
1
C5
Capacitor, X7R, 1000pF, 25V, 20%, 0402
AVX, 04023C102MAT2A
5
1
C7
Capacitor, X7R, 680pF, 25V, 10%, 0402
AVX, 04023C681KAT2A
6
1
C8
Capacitor, X5R, 0.47μF, 10V, 10%, 0603
Taiyo Yuden, LMK107BJ474KA-T
7
1
C11
Capacitor, X5R, 2.2μF, 10V, 20%, 0603
Taiyo Yuden, LMK107BJ225MA-T
8
1
L1
Inductor, 3.3μH, IHLP-2525EZ-01 (SERIES)
Vishay, IHLP2525EZER3R3M01
9
1
R1
Resistor/Jumper, Chip, 0Ω, 1/16W, 1A, 0402
Vishay, CRCW04020000Z0EA
10
1
R3
Resistor, Chip, 100k, 0.06W, 5%, 0402
Vishay, CRCW0402100KJNED
11
1
R4
Resistor, Chip, 316k, 0.06W, 1%, 0402
Vishay, CRCW0402316KFKED
12
1
R5
Resistor, Chip, 45.3k, 0.06W, 1%, 0402
Vishay, CRCW040245K3FKED
13
1
R6
Resistor, Chip, 102k, 0.06W, 1%, 0402
Vishay, CRCW0402102KFKED
14
1
R7
Resistor, Chip, 21.5k, 0.06W, 1%, 0402
Vishay, CRCW040221K5FKED
15
1
U1
IC, Buck Regulator, QFN(26) (UFEMA) 4mm × 6mm
Linear Technology, LT3690EUFE
Sanyo, 63CE22BS
Additional Circuits
16
0
C1 (OPT)
Capacitor, Alum 22μF, 63V, 25%, OSCON-CE-6.3
17
0
C6, C9, C10 (OPT)
Capacitor, 0402
18
0
R2 (OPT)
Resistor, 0402
Hardware/Components (For Demo Board Only)
19
6
E1-E6
Turret, Testpoint 0.094"
Mill Max, 2501-2-00-80-00-00-07-0
20
2
JP1, JP2
Header, 3-Pin, 0.079 Single Row
Samtec, TMM-103-02-L-S
21
2
XJP1, XJP2
Shunt, 2mm Ctrs.
Samtec, 2SN-BK-G
dc1520af
4
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.
A
B
C
D
5
',6
(1
*1'
-3
(1$%/(
(
(
9,1
99
975$16,(17
+
&
X)
9
237
9,1
6
&
S)
6
4
&
237
4
5
2KP
&
S)
5
.
&
X)
9
/7(8)(
8
237
5
&
X)
9
VCCINT
VC
SS
EN
UVLO
VIN
VIN
VIN
GND
GND
GND
GND
6
SYNC
RT
FB
PG
SW
SW
SW
SW
SW
SW
SW
SW
SW
BOOST
3
/
X+
&
237
.
N+]
5
X)
9
&
6
3
7+,6&,5&8,7,635235,(7$5<72/,1($57(&+12/2*<$1'
6833/,(')2586(:,7+/,1($57(&+12/2*<3$576
&?3$'6352-(&76?$?6&+?$BB5(9'61
5%
6&$/( 121(
02//<=
2
6
5
.
5
.
'$7(
2
),;(')5(4
DATE
/7&&21),'(17,$/)25&86720(586(21/<
0F&DUWK\%OYG
0LOSLWDV&$ www.linear.com
3KRQH
)D[
%856702'(
02//<=
<,1*&
APPROVED
1
,&12
7KXUVGD\)HEUXDU\
1
/7(8)(
'(02&,5&8,7$
6+((7
2)
5(9
9$32:(56<1&+521286%8&.5(*8/$725
T
1$
6,=(
-3
02'(
6<1&
3*
*1'
9287
9#$
TECHNOLOGY
(
(
(
&
X)
9
(
DESCRIPTION
352'8&7,21
$''&
REVISION HISTORY
7,7/( 6&+(0$7,&
&
237
5
.
APPROVALS
&
X)
9
REV
ECO
/,1($57(&+12/2*<+$60$'($%(67())25772'(6,*1$
&,5&8,77+$70((76&86720(56833/,('63(&,),&$7,216
+2:(9(5,75(0$,167+(&86720(5
65(63216,%,/,7<72
3&%'(6
9(5,)<3523(5$1'5(/,$%/(23(5$7,21,17+($&78$/
$33(1*
$33/,&$7,21&20321(1768%67,787,21$1'35,17('
&,5&8,7%2$5'/$<2870$<6,*1,),&$17/<$))(&7&,5&8,7
3(5)250$1&(255(/,$%,/,7<&217$&7/,1($5
7(&+12/2*<$33/,&$7,216(1*,1((5,1*)25$66,67$1&(
&86720(5127,&(
BIAS
GND
5
A
B
C
D
DEMO MANUAL DC1520A
SCHEMATIC DIAGRAM
dc1520af
5
DEMO MANUAL DC1520A
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.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
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.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
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.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1520af
6
Linear Technology Corporation
LT 0211 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2011