Linear Technology DC1891A Quick setup guide

1
dc1891af
DEMO MANUAL DC1891A
DESCRIPTION
LTC3862-2
Low Noise PolyPhase
®
SEPIC
DC/DC Converter
Demonstration circuit 1891A is a 2-phase high efficiency
nonisolated SEPIC (single ended primary inductor con-
verter) converter featuring the LTC
®
3862-2 switching
controller. The DC1891A converts a 6V to 60V input to
a12V output and provides 6A of output current. The
converter operates at 300kHz (600kHz output ripple) with
efficiency around 90%. With a proper amount of airflow,
the DC1891A converter can generate over 6A of output
current. The DC1891A can be easily modified to generate
output voltages in the range from 0.8V to 48V.
L, LT, LTC, LTM, Linear Technology, PolyPhase and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
PERFORMANCE SUMMARY
Also,theDC1891Acanbeoptimized forspecificinputvolt-
ages. The narrowing of input voltage range can increase
theconverter’sefficiency.Therefore,anarrowinputvoltage
range is more desirable.
The LTC3862-2 can be synchronized to an external clock
of up to 400kHz. Please refer to LTC3862-2 data sheet for
design details and applications information.
Design files for this circuit board are available at
http://www.linear.com/demo
PARAMETER CONDITIONS VALUE
Minimum Input Voltage IOUT = 0A to 6A 6V
Maximum Input Voltage IOUT = 0A to 6A 60V
VOUT VIN = 6V to 60V, IOUT = 0A to 6A 12V ±3%
Typical Output Ripple VOUT VIN = 6V to 60V, IOUT = 0A to 6A 100mVP-P
Nominal Switching Frequency 300kHz
Specifications are at TA= 25°C

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dc1891af
DEMO MANUAL DC1891A
QUICK START PROCEDURE
Demonstration circuit 1891A is easy to set up to evaluate
theperformanceoftheLTC3862-2circuit.RefertoFigure1
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. See Figure 2 for
the proper scope probe technique.
1. With power off, connect the input power supply to VIN
and GND. Make sure that the input power supply has
sufficient current rating at minimum input voltage for
the required output load.
2. Turn on the power at the input.
NOTE: Make sure that the input voltage does not exceed
60V.
3. Check for the proper output voltage.
VOUT = 12V, ±3%.
If there is no output, temporarily disconnect the load
to make sure that the load is not set too high.
4. Oncetheproperoutputvoltage isestablished,adjustthe
load within the operating range and observe the output
voltage regulation, ripple voltage, efficiency and other
parameters.
5. The DC1891A is equipped with an input capacitor CIN4
that is optional and is used to help with filtering when
the board is connected to the lab supply with long leads.
The capacitor CIN4 can be removed if the input power
source is close and has low source impedance.
CHANGING THE OUTPUT VOLTAGE
To set the output voltage lower or higher than 12V, change
the bottom voltage divider resistor connected to the FB
pin of U1 (see the Schematic Diagram). Also, check the
MOSFET, output diode and capacitor voltage ratings if the
output voltage is set higher than 12V.
The optional Q5 circuit is used to get the circuit running.
Once the circuit is running, the 12V output is used to
bias U1 via D2. The start-up circuit Q5 is turned off by Q6
when VOUT gets to the level set by D3, R14 and R16 that
activates Q6. Please contact the LTC factory for details.

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dc1891af
DEMO MANUAL DC1891A
Figure 1. Proper Measurement Equipment Setup
QUICK START PROCEDURE
Figure 2. Measuring Input or Output Ripple
DC1891a F01
GND VIN
DC1891a F02

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dc1891af
DEMO MANUAL DC1891A
QUICK START PROCEDURE
Figure 3. Reducing the Input Voltage Range and Selecting
More Optimal MOSFET, Diode and Inductor Can Optimize the
Efficiency of DC1891A
Figure 4. Fast Transient Response of DC1891A is Achieved with a
Small Amount of Output Capacitance
Figure 5. The DC1891A Ramps the Output Slowly at Start-Up
without Generating an Input Current Surge
OUTPUT LOAD STEP RESPONSE
The load step response of DC1891A is very fast even
though a relatively small amount of output capacitance
is present (188µF ceramic and 440µF electrolytic). The
load step transients are shown in Figure 4. To improve
load step response further or to reduce the output ripple,
more output capacitance can be added. Low ESR output
capacitors will have the greatest effect on reducing the
ripple and load step transients.
SOFT-START FUNCTION
The DC1891A features a soft-start circuit that controls the
inrush current and output voltage ramp at start-up. The
capacitor CSS controls the start-up period. The start-up
waveforms are shown in Figure 5.
IOUT (A)
0
EFFICIENCY (%)
88
86
84
82
80
78
76
74
90
6
DC1891a F03
72
70 38
92
4
127
5
6V INPUT
12V INPUT
24V INPUT
48V INPUT
DC1891a F04
VOUT 200mV/DIV
IOUT 2A/DIV
VIN = 12V, VOUT = 12V
IOUT = 1A
3A LOAD STEP
500µs/DIV
DC1891a F05
VOUT 2V/DIV
50ms/DIV
IIN 2A/DIV
VIN = 12V, VOUT = 12V
IOUT = 5A
START-UP

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dc1891af
DEMO MANUAL DC1891A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 CC2 CAP, NPO 100pF, 25V, 5%, 0603 AVX 06033A101JAT2A
2 4 C3, C4, CSS, C5 CAP, X7R 0.01µF 25V 10% 0603 AVX 06033C103KAT2A
3 1 CC1 CAP, X5R 0.015µF 25V 10% 0603 AVX 06033D153KAT2A
4 1 C1 CAP, NPO 1000pF 25V 10% 0603 AVX 06033A102JAT2A
5 1 C2 CAP, X5R, 2.2µF, 25V, 10%, 0805 AVX 08053D225KAT2A
6 1 CIN4 CAP, 33µF, 63V SUN ELECT, 63HVH33MS
7 1 CU1 CAP, X7R 4.7µF 50V 10% 1206 MURATA GRM31CR71H475KA12L
8 7 CS1 TO CS4, CIN1 TO CIN3 CAP, X7S 4.7µF 100V 20% 1812 TDK C4532X7S2A475M
9 4 COUT1 TO COUT4 CAP, X7S 47µF 16V 20% 1812 TDK CKG45NX7S1C476M
10 2 COUT5, COUT6 CAP, 220µF 16V APXE UNITED CHEMI-CON APX160ARA221MHA0G
11 1 CF CAP, X7R 0.01µF 16V 10% 0603 AVX 0603YC103KAT2A
12 2 D3, D5 ZENER DIODE, SOD-323 NXP SEMI PDZ6.8B
13 1 D4 DIODE, SOD-523 NXP SEMI BAS516
14 2 D1, D2 SCHOTTKY RECTIFIER, TO-277A VISHAY V8P10-M3/86A
15 2 Q2, Q4 POWER MOSFET, PG-TDSON-8 INFINEON BSC060N10NS3G
16 1 Q5 PNP TRANSISTOR, SOT-23 NXP SEMI PBSS9110T
17 2 Q6, Q8 NPN TRANSISTOR, SOT-323 NXP SEMI PMST5550
18 1 Q7 NPN TRANSISTOR, SC-75 NXP SEMI BC847T
19 1 RC1 RES, CHIP 13.7k, 1% 0603 VISHAY CRCW060313K7FKEA
20 1 ROSC RES, CHIP 43.2k, 1% 0603 VISHAY CRCW060343K2FKED
21 2 R4, R10 RES, CHIP 10Ω 5% 0603 VISHAY CRCW060310R0JNEA
22 2 RF, R17 RES, CHIP 0Ω, Jumper 0603 VISHAY CRCW06030000Z0EA
23 1 R9 RES, CHIP 110k, 1% 0805 VISHAY CRCW0805110KFKEA
24 1 R1 RES, CHIP 12.4k, 1% 0603 VISHAY CRCW060312K4FKEA
25 1 R3 RES, CHIP 845k, 1% 0603 VISHAY CRCW0603845KFKEA
26 1 R11 RES, CHIP 249k, 1% 0603 VISHAY CRCW0603249KFKEA
27 2 R6, R8 RES, 0.005Ω, 1/2W, 1%, 2010 VISHAY WSL20105L000FEA
28 1 R12 RES, CHIP 33k, 1% 0603 VISHAY CRCW060333K0FKEA
29 1 R13 RES, CHIP 220k, 1% 0603 VISHAY CRCW0603220KFKEA
30 1 R14 RES, CHIP 56k, 1% 0603 VISHAY CRCW060356K0FKEA
31 2 R15, R16 RES, CHIP 10k, 1% 0603 VISHAY CRCW060310K0FKEA
32 1 R19 RES, CHIP 100k, 1% 0603 NIC NRC06F1003TRF
33 1 R20 RES, CHIP 180k, 1% 0603 VISHAY CRCW0603180KFKEA
34 2 T1,T2 COUPLED INDUCTOR, 6.8µH WÜRTH 7448709068
35 1 U1 PWM CONTROLLER LTC3862EFE-2 LINEAR TECHNOLOGY LTC3862EFE-2

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DEMO MANUAL DC1891A
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Additional Demo Board Circuit Components
1 0 Q1, Q3 (OPT) MOSFET, PG-TDSON-8
2 0 R18 (OPT) RES, CHIP 0603
3 0 R7, R5 (OPT) RES, CHIP 2010
Hardware: For Demo Board Only
1 6 E3 TO E8 TESTPOINT, TURRET, 0.094" MILL-MAX 2501-2-00-80-00-00-07-0
2 2 E1, E2 STUD, TEST PIN PEM KFH-032-10ET
3 4 E1, E2 (2 each) NUT BRASS, # 10-32 M/S BR PL ANY 10-32
4 2 E1, E2 RING, LUG # 10 KEYSTONE, 8205
5 2 E1, E2 WASHER #10, TIN PLATED BRASS ANY #10EXT BZ TN
6 4 JP1 TO JP4 HEARDER, 3PIN 1 ROW 0.079CC SULLINS NRPN031PAEN-RC
7 4 JP1 TO JP4 SHUNT, 0.079" CENTER SAMTEC 2SN-BK-G
8 1 SW1 SWITCHE, SEALED TOGGLE C&K GT11MCBE (THRU-HOLE)
9 4 STAND-OFF STAND-OFF, NYLON 0.50" TALL KEYSTONE 8833(SNAP ON)
10 1 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 1891A
PARTS LIST

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dc1891af
DEMO MANUAL DC1891A
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
A A
B B
C C
D D
E E
4 4 3 3 2 2 1 1
BLANK SLOPE DMAX
Optional Bias Circuit
PHASE
1.0**
0.625
1.66
75%
84%**
96%
325ns
250ns**
175ns
120°
180°
RUN
OFF ON
.005 1W
.005 1W
OPT
OPT
LTC3862EFE-2
6V-60V
12V / 6A
GORAN P.
OPT OPT
See Demo Manual
HVH
APXE
100V 100V
100V 100V
*
*
*
VOUT
+VIN
+VIN
+VIN
VOUT Vu1
Vu1
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
Goran P.PRODUCTION25-23-12
__
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
Goran P.PRODUCTION25-23-12
__
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
Goran P.PRODUCTION25-23-12
__
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
Wednesday, August 01, 2012
11
LOW NOISE POLYPHASE SEPIC POWER CONVERTER
HZ
N/A
LTC3862EFE-2 DEMO CIRCUIT 1891A
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
Wednesday, August 01, 2012
11
LOW NOISE POLYPHASE SEPIC POWER CONVERTER
HZ
N/A
LTC3862EFE-2 DEMO CIRCUIT 1891A
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
Wednesday, August 01, 2012
11
LOW NOISE POLYPHASE SEPIC POWER CONVERTER
HZ
N/A
LTC3862EFE-2 DEMO CIRCUIT 1891A
R1 12.4kR1 12.4k
CC2 100pF CC2 100pF
JP1JP1
1
2
3
E3E3
RC1 13.7k RC1 13.7k
R9
110k
R9
110k
R8R8
COUT2COUT2
Q1Q1
P10P10
E5
GND
E5
GND
CU1 4.7uFCU1 4.7uF
R15
10k
R15
10k
JP2JP2
1
2
3
R6R6 Q2
BSC060N10NS3G
Q2
BSC060N10NS3G
CC1 15nF CC1 15nF
D5
PDZ6.8B
D5
PDZ6.8B
2 1
RF 0RF 0
R10 10R10 10
U1U1
BLANK
3
PHASEMODE
4
FREQ
5
SS
6
ITH
7
FB
8
SGND
9
CLKOUT
10
SYNC
11
PLLFLTR
12
SENSE2+ 13
SENSE2- 14
NC 15
G2 16
PGND 17
G1 18
INTVCC 19
VIN 20
RUN 21
SENSE1- 22
SENSE1+ 23
3V8 24
DMAX
1
SLOPE
2
GND
25
R13
220k
R13
220k
R14 56k R14 56k
Q6
PMST5550
Q6
PMST5550
1
2 3
P11P11
C2 2.2uF C2 2.2uF
R19 100k R19 100k
COUT3COUT3
SW1SW1
1
2
3
JP3JP3
1
2
3
R3 845kR3 845k
R20 180kR20 180k
E4
+VOUT
E4
+VOUT
CIN3CIN3
Q5
PBSS9110T
Q5
PBSS9110T
1
2 3
+
COUT6
+
COUT6
E1
+VIN
E1
+VIN
Q8
PMST5550
Q8
PMST5550
1
2 3
CSS 10nFCSS 10nF
E6
GND
E6
GND
+
COUT5
220uF 16V
+
COUT5
220uF 16V
CS4 4.7uFCS4 4.7uF
ROSC 43.2kROSC 43.2k
D4
BAS516
D4
BAS516
2 1
C4 10nF C4 10nF
R16 10k R16 10k
T1
6.8uH
7448709060 T1
6.8uH
7448709060
3 4 1 2
CIN1 4.7uF
100V
CIN1 4.7uF
100V
JP4JP4
1
2
3
Q4
BSC060N10NS3G
Q4
BSC060N10NS3G
D2
V8P10
D2
V8P10
CIN2CIN2
CS2 4.7uFCS2 4.7uF
E7
GND
E7
GND
C5 10nF C5 10nF
C1 1nFC1 1nF
COUT1
47uF
16V
COUT1
47uF
16V
R7R7
+
CIN4
33uF 63V
+
CIN4
33uF 63V
Q7
BC847T
Q7
BC847T
1
2 3
Q3Q3
E2
GND
E2
GND
R17 0R17 0
T2
6.8uH
7448709060 T2
6.8uH
7448709060
34 12
R5R5
D3
PBZ6.8B
D3
PBZ6.8B
2 1
CS1 4.7uFCS1 4.7uF
R4 10R4 10
COUT4COUT4
R12 33k R12 33k
R18 OPTR18 OPT
R11 249kR11 249k
E8
GND
E8
GND
C3 10nF C3 10nF
CS3 4.7uFCS3 4.7uF
CF
0.01uF
CF
0.01uF
D1
V8P10
D1
V8P10

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dc1891af
DEMO MANUAL DC1891A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2012
LT 0812 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) provides the enclosed product(s) under the following AS IS conditions:
Thisdemonstration board (DEMOBOARD) kit beingsold or providedby LinearTechnology isintended for usefor 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. LT C 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 applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation

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