Linear LT3995 Quick setup guide

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DEMO MANUAL DC1832A
Description
LT3995
60V, 3A, 2MHz Step-Down
Switching Regulator with
2.7µA Quiescent Current
Demonstration circuit 1832A is a monolithic step-down
DC/DC switching regulator featuring the LT3995. The
LT3995isacompact,highefficiencymonolithicstep-down
switching regulator thatconsumes only2.7μAofquiescent
current. The demo circuit is designed for 3.3V, 3A output
from a 4.3V to 60V input. The switching frequency can be
programmed either via oscillator resistor or external clock
up to 2MHz. To synchronize to an external clock, move
JP2 to SYNC and apply the external clock to the SYNC
turret. The RT resistor (R5) should be chosen to set the
LT3995 internal switching frequency at least 20% below
the lowest synchronization input frequency.
Low ripple Burst Mode
®
operation increases the effi-
ciency at the light load while keeping the output ripple
below15mV.The SYNC pin on the demo board is grounded
by default by setting JP2 at RT FREQ for low ripple
Burst Mode operation. Figure1 shows the demo board
efficiency at 12V input voltage.
The LT3995 is in shutdown when the EN pin is low and
active when the pin is high. The threshold of the EN pin
is accurate at 1.02V with 60mV of hysteresis. Users can
populate R7 and R8 to provide a programmable under L, LT, LTC, LTM, 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.
voltage lockout. A low dropout voltage of 500mV is main-
tainedwhentheinputvoltagedropsbelowtheprogrammed
output voltage. During a short-circuit fault, the LT3995
has current limit foldback to limit the power dissipation.
The demo board has an EMI filter installed. The EMI
performance of the demo board at 12V input voltage is
shown on Figure 2. The limit in Figure 2 is EN55022 Class
B. The figure shows the circuit passes the test with a wide
margin. To use the EMI filter, the input should be tied to
VEMI not VIN.
The LT3995 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 1832A. The LT3995 is assembled in a 16-
lead plastic MSOP package with an exposed pad for low
thermal resistance. Proper board layout is essential for
bothproperoperationandmaximumthermalperformance.
See the data sheet sections for details.
Design files for this circuit board are available at
http://www.linear.com/demo
Figure 1. LT3995 Efficiency vs Load Current,
12VIN to 3.3VOUT Efficiency
Figure 2. LT3995 Demo Board EMI Performance
(Switching Frequency = 300kHz, VIN = 12V)
LOAD CURRENT (A)
EFFICIENCY (%)
dc1832a F01
0
40
50
60
70
0.5 11.5 2 2.5
80
90
45
55
65
75
85
3
10dB/DIV LOG, REF 70.00dBµV
dc1832a F02
START 150kHz
RES BW (CISPR) 9kHz
TRACE 1 PASS
–30
–10
10
30
VBW 62kHz
50
70
–20
0
20
40
60
STOP 30.00 MHz
SWEEP 717ms (6637pts)

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DEMO MANUAL DC1832A
Quick start proceDure
Demonstration circuit 1832A is easy to set up to evalu-
ate the performance of the LT3995. Refer to Figure 3
for proper measurement equipment setup and use the
following procedure.
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. See Figure 4 for the proper
scope technique.
1. Place JP1 on the ON position.
2. Place JP2 on the RT FREQ position.
3. With power off, connect the input power supply to VIN
and GND. Make sure that the input voltage does not
exceed 60V.
4. With power off, connect load from VOUT to GND.
5. Turn on the power at the input.
6. 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 or
is shorted.
7. 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.
8. An external clock can be added to the SYNC terminal
when SYNC function is used (JP2 on the SYNC posi-
tion). Please make sure that the SYNC frequency is at
least 20% higher than the set switching frequency.
See the data sheet Synchronization section.
performance summary
PARAMETER CONDITIONS VALUE
Guaranteed Minimum Input Voltage 4.3V
Maximum Input Voltage 60V
Output Voltage VOUT VIN = 4.3V ~ 60V 3.275V ± 3%
Switching Frequency RT= 182k 300kHz ± 20%
Guaranteed Maximum Output Current IOUT VIN = 4.3V ~ 60V 3A
Typical Efficiency VIN = 12V, IOUT = 3A 82.2%
Typical Output Voltage Ripple VIN = 12V, IOUT = 3A 11mV
Specifications are at TA= 25°C

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DEMO MANUAL DC1832A
Figure 3. Proper Measurement Equipment Setup
Figure 4. Measuring Input or Output Ripple
Quick start proceDure

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DEMO MANUAL DC1832A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C1, C8 CAP., X5R, 47µF, 10V, 20%, 1210 TDK, C3225X5R1A476M
2 1 C2 CAP., X5R, 0.47µF, 25V, 10%, 0603 TDK, C1608X5R1E474M
3 2 C3, C7 CAP., X7R, 2.2µF, 100V, 10%,1210 TDK, C3225X7R2A225M
4 1 C5 CAP., C0G, 10pF, 50V, 10%, 0402 TDK, C1005C0G1H100D
5 1 C6 CAP., X7R, 10nF, 25V, 10%, 0402 TDK, C1005X7R1E103K
6 1 C11 CAP., X5R, 1µF, 10V, 10%, 0603 TDK, C1608X5R1A105K
7 1 C12 CAP., X7R, 0.1µF, 100V, 10%, 0603 MURATA, GRM188R72A104KA35D
8 1 D1 DIODE, PDS360 PowerDi5 DIODE INC., PDS360
9 1 L1 IND, 8.2µH COILCRAFT, XAL6060-822ME
10 1 R1 RES., CHIP, 1.00M, 1/16W, 1%, 0402 NIC, NRC04F1004TRF
11 1 R2 RES., CHIP, 576k, 1/16W, 1%, 0402 NIC, NRC04F5763TRF
12 1 R5 RES., CHIP, 182k, 1/16W, 1%, 0402 NIC, NRC04F1823TRF
13 1 R6 RES., CHIP, 200k, 1/16W, 1%, 0402 NIC, NRC04F2003TRF
14 1 U1 I.C., LT3995EMSE, MSE16 LINEAR TECHNOLOGY, LT3995EMSE
Additional Demo Board Circuit Components
1 1 C4 CAP., ALUM., 100µF, 100V, 10% SUN ELECT, 100CE100KXT
2 2 C9, C10 CAP., X7R, 2.2µF, 100V, 10%, 1210 TDK, C3225X7R2A225M
3 1 C13 CAP., HVP SERIES, 33µF, 63V, 20% SUNCON, 63HVP33M
4 1 L2 IND, 1.0µH VISHAY, IHLP-1616BZER1R0M01
5 1 L3 IND, 3.3µH VISHAY, IHLP-2020BZER3R3M01
6 0 R7,R8 RES., 0603 OPT
Hardware: For Demo Board Only
1 7 E1, E2, E3, E4, E5, E6, E7 TURRET, 0.094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 2 E8, E9 TESTPOINT, TURRET, 0.061" PBF MILL-MAX, 2308-2-00-80-00-00-07-0
3 2 JP1, JP2 JMP, 1X3-079 SAMTEC, TMM-103-02-L-S
4 2 XJP1, XJP2 SHUNT, 2mm CTRS. SAMTEC, 2SN-BK-G

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DEMO MANUAL DC1832A
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
NOTE: UNLESS OTHERWISE SPECIFIED
SUNCON 100CE100KXT
ALL CAPACITORS ARE IN MICROFARADS, 0402.
1. ALL RESISTORS ARE IN OHMS, 0402.
VIN
VIN
VOUT
JP2
SYNC RT FREQ
JP2
SYNC RT FREQ
1 3 2
D1 PDS360 D1 PDS360
2 1
3
C9
2.2uF
100V
1210
C9
2.2uF
100V
1210
C10
2.2uF
100V
1210
C10
2.2uF
100V
1210
E6
PG
E6
PG
E5
EN/UVLO
E5
EN/UVLO
+
C4 100uF 100V
+
C4 100uF 100V
C7 2.2uF 100V 1210 C7 2.2uF 100V 1210
C6 10nF C6 10nF
R7
OPT 0603
R7
OPT 0603
R5 182k 1% (300kHz) R5 182k 1% (300kHz)
E4
GND E4 GND
C11 1uF
0603
10V C11 1uF
0603
10V
E3
VIN
4.3V - 60V E3
VIN
4.3V - 60V
L2
1.0uH
IND-IHLP1616BZ-01
L2
1.0uH
IND-IHLP1616BZ-01
C2 0.47uF 0603 C2 0.47uF 0603
E2 GND E2 GND
R6 200K R6 200K
E8
VEMI
E8
VEMI
C3 2.2uF 100V 1210 C3 2.2uF 100V 1210
U1
LT3995EMSE
U1
LT3995EMSE
NC
9
OUT 3
FB 1
SS
2
EN
13
VIN
12
BOOST 4
SW 5
PG
15
SYNC 16
GND
17
VIN
11 VIN 10
SW 6 SW 7
RT 14
NC
8
JP1
ON
OFF
JP1
ON
OFF
1 3 2
E9
GND
E9
GND
E7 SYNC E7 SYNC
R2 576k 1% R2 576k 1%
R8
OPT 0603
R8
OPT 0603
+
C13
33uF
63V
63HVP33
+
C13
33uF
63V
63HVP33
E1
VOUT
3.3V / 3A
E1
VOUT
3.3V / 3A
L1
8.2uH
L1
8.2uH
C1 47uF 10V 1210 C1 47uF 10V 1210
R1 1.00M 1% R1 1.00M 1%
L3
3.3uH
IND-IHLP2020BZ-01
L3
3.3uH
IND-IHLP2020BZ-01
C8 47uF 10V 1210 C8 47uF 10V 1210
C5 10pF C5 10pF
C12 0.1uF
0603 100V
C12 0.1uF
0603 100V

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DEMO MANUAL DC1832A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2013
LT 0513 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) 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 LT C 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
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observe good laboratory practice standards. Common sense is encouraged.
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