Linear Technology DC2251A Quick setup guide

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dc2251af
DEMO MANUAL DC2251A
Description
LTM8065
40V, 2.5A Silent Switcher
µModule Regulator
Demonstration circuit 2251A is a 40V, 3.5A peak, 2.5A
continuous step-down μModule
®
regulator featuring the
LTM
®
8065. The demo board is designed for 5V output
from a 6V to 40V input. The wide input range allows a
variety of input sources, such as automotive batteries and
industrial supplies. The user adjustable features of the
LTM8065 such as output voltage, switching frequency,
soft-start and power good can be changed on DC2251A
simply by modifying the appropriate resistors and/or
capacitors.
The LTM8065 can be programmed to different operation
modes. The SYNC pin on the demo board is grounded
(JP1 at BURST position) by default for low ripple Burst
Mode
®
operation. Pulse-skipping mode, spread spectrum
mode or synchronization mode can be selected respec-
tively by moving JP1 shunt to SYNC position and adding
different signals to SYNC terminal. See Quick Start Pro-
cedure section for more details.
L, LT, LTC, LTM, Linear Technology, Burst Mode, µModule and the Linear logo are registered
trademarks of Analog Devices, Inc. All other trademarks are the property of their respective
owners.
BoarD photo
Figure 1 shows the efficiency of the circuit under differ-
ent input voltages in Burst Mode operation. The rated
maximum continuous load current is 2.5A, while derating
is necessary for certain input voltage and thermal condi-
tions. Figure 2 shows the LTM8065 derating curve on
DC2251A demo board. The demo board has an optional
EMI filter. To achieve high EMI/EMC performance, the
input EMI filter is required and the input voltage should
be applied at VIN_EMI terminal.
The LTM8065 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 demo circuit 2251A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2251A

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DEMO MANUAL DC2251A
Quick start proceDure
Demonstration circuit 2251A is easy to set up to evalu-
ate the performance of the LTM8065. Refer to Figure 3
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 output voltage ripple by
touching the probe tip directly across the output capacitor.
See Figure 4 for the proper scope technique.
1. Place JP1 on BURST position.
2. With power off, connect the input power supply to VIN
and GND. If the input EMI filter is desired, install the
filter and connect the input power supply to VIN_EMI
and GND.
3. With power off, connect the load from VOUT to GND.
4. Turn on the power at the input.
NOTE. Make sure that the input voltage does not exceed
40V.
5. Check for the proper output voltage (VOUT = 5V).
NOTE. If there is no output, temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
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.
Figure 1. LTM8065 Demo Circuit DC2251A Efficiency vs. Load
Current (fSW = 1MHz, VOUT = 5V, Burst Mode Operation)
Figure 2. LTM8065 Demo Circuit DC2251A
Maximum Load Current Derating
performance summary
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN* Input Supply Range 6 40 V
VOUT Output Voltage 4.85 5 5.15 V
IOUT** Maximum Continuous Output Current 2.5 A
fSW Switching Frequency VIN = 12V , IOUT = 2.5A 1 MHz
EFE Efficiency at DC VIN = 12V , IOUT = 2.5A 91.5 %
* When VIN voltage is low, the LTM8065 may skip switching cycles.
** Derating is necessary for certain VIN and thermal conditions.
LOAD CURRENT (A)
0.001
0.01
0.1
1
10
55
65
75
85
95
EFFICIENCY (%)
DC2251A F01
12V
IN
24V
IN
0 LFM
12V
IN
24V
IN
36V
IN
AMBIENT TEMPERATURE (°C)
0
25
50
75
100
125
0
1
2
3
4
MAXIMUM LOAD CURRENT (A)
DC2251A F02

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DEMO MANUAL DC2251A
Quick start proceDure
Figure 4. Proper Measurement Equipment Setup
7. JP1 is placed on BURST position by default, for the low
ripple Burst Mode operation. When JP1 is placed on
SYNC position,LTM8065can operate in pulse-skipping
mode,spread spectrum mode or synchronization mode
respectively, based on the different SYNC terminal
inputs. If SYNC terminal is floating, LTM8065 is in
pulse-skipping mode. If an external clock is driving the
SYNC terminal, LTM8065 is in synchronization mode.
Please make sure that RT should be choseN to set the
LTM8065 switching frequency equal to or below the
lowest SYNC frequency. If a 2.9V to 4.2V DC voltage
is tied to the SYNC terminal, LTM8065 is in spread
spectrum mode. This DC voltage can also be added
through a voltage divider (R7 and R8) from the output.
Therecommendeddividerbottomresistor (R8) is 200k.
DC2251A F03
+
–
+–
VOUT
IOUT
–
+
+–
–
+
LOAD
VIN
IIN
POWER
SUPPLY
+
–
Figure 3. Measuring Output Ripple
+
–
VOUT
GND
C5
DC2251A F04

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DEMO MANUAL DC2251A
Quick start proceDure
Figure 5. DC2251A Output Noise Spectrum, VIN = 12V, VOUT = 5V, IOUT = 2.5A, fSW = 1MHz
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 CAP., X5R, 47µF, 10V, 20%, 0805 MURATA, GRM21BR61A476ME15L
2 1 C2 CAP., X5R, 4.7µF, 50V, 10%, 0805 MURATA, GRM21BR61H475KE51L
3 1 C3 CAP., X7R, 0.1µF, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D
4 1 C5 CAP., X5R, 10µF, 25V, 20%, 0603 MURATA, GRM188R61E106MA73D
5 1 C10 CAP., X7R, 0.1µF, 50V, 10%, 0402 TDK, CGA2B3X7R1H104K050BB
6 2 R1, R5 RES., CHIP, 100k, 1/10W, 1%, 0603 VISHAY, CRCW0603100KFKEA
7 1 R2 RES., CHIP, 60.4k, 1/10W, 1%, 0603 VISHAY, CRCW060360K4FKEA
8 1 R3 RES., CHIP, 41.2k, 1/10W, 1%, 0603 VISHAY, CRCW060341K2FKEA
9 1 U1 IC., BGA, 36L, 6.25mm × 6.25mm × 2.32mm LINEAR TECH., LTM8065EY#PBF
Additional Demo Board Circuit Components
1 0 C4, C11 (OPT) CAP., 0603
2 0 C6 (OPT) CAP., X7R, 4.7µF, 50V, 10%, 1206
3 0 C8 (OPT) CAP., X7R, 0.1µF, 50V, 10%, 0402
4 1 C9 CAP., ALUM, 22µF, 63V, 20% SUN ELECTRONIC INDUSTRIES CORP., 63CE22BS
5 0 L1 (OPT) IND, 2.2µH, 4.45mm ×4.06mm WURTH ELEKTRONIK, 74437324022
6 1 R4 RES., CHIP, 0, 1/10W, 0603 VISHAY, CRCW06030000Z0EA
7 0 R6, R7, R8 (OPT) RES., 0603
Hardware: For Demo Board Only
1 10 E1-E6, E8-E11 TESTPOINT, TURRET, 0.094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0
2 0 E7 (OPT) TESTPOINT, TURRET, 0.094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0
3 1 JP1 HEADER 3 PIN 0.079 SINGLE ROW WURTH ELEKTRONIK, 62000311121
4 1 XJP1 SHUNT, 0.079" CENTER WURTH ELEKTRONIK, 60800213421
5 4 MH1-MH4 STAND-OFF, NYLON, 0.375" SNAP ON KEYSTONE, 8832
FREQUENCY (MHz)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
–120
–100
–80
–60
–40
–20
0
INTENSITY (dBm)
DC2251A F05

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DEMO MANUAL DC2251A
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
ALL CAPACITORS ARE 0603.
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE 0603.
INPUT EMI FILTER
*
*
SEE DEMO MANUAL
*
OPTIONAL
VOUT
E7
VIN_EMI
OPT
+
C9
22uF
63V
63CE22BS
JP1
BURST
SYNC
1 3
2
E6
TR/SS
C2 4.7uF 50V 0805
E3
PG
E11
SYNC
R2
60.4K
C4 OPT
L1
74437324022
Wurth Elektronik
2.2uH
LTM8065EY
U1
PG
A3
GND
A4
RT
A5
FB
B1
AUX
B2
TR/SS
B5
RUN
B6
BIAS
A2
SYNC
B4
VOUT
F1
VOUT
F2
VOUT
F3
VOUT
F4
VOUT
F5
VOUT
F6
VIN
C3
VIN
C4
VIN
C5
VIN
C6
GND
A1
GND
A6
GND
B3
GND
C1
GND
C2
GND
D1
GND
D2
GND
D3
GND
D4
GND
D5
GND
D6
GND
E1
GND
E2
GND
E3
GND
E4
GND
E5
GND
E6
C6 50V 1206 4.7uF
E4
GND
E8
BIAS
E5
GND
E1
VIN
6V - 40V
C11 OPT
E9
VOUT
5V / 2.5A
R1
100K
R5 100K
C1 47uF 10V 0805
R8
OPT
E10
GND
R3
41.2K
C10
0.1uF
50V
0402
R6 OPT
C3 0.1uF 16V
E2
RUN
C8 50V 0402 0.1uF
R7
OPT
C5 10uF 25V
R4
0
VIN
VOUT
VIN
VOUT

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DEMO MANUAL DC2251A
 LINEAR TECHNOLOGY CORPORATION 2017
LT 1017 • 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
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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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customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
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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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