Analog Devices DC3103A User manual

1
DEMO MANUAL DC3103A
Rev. 0
DESCRIPTION
LT3942
36V 4-Switch Buck-Boost
Voltage Regulator
Demonstration circuit DC3103A is a monolithic 4-Switch
buck-boost voltage regulator featuring the LT
®
3942. It
has been designed with an output voltage set to 12V with
capability of delivering up to 1A when the input voltage is
between 7V and 36V. The demonstration circuit continues
operating with an input voltage as low as 3V with reduced
output power capability. DC3103A is configured for 2MHz
switching frequency with spread spectrum frequency
modulation (SSFM) disabled. When enabled, SSFM
adjusts the switching frequency of the LT3942 between
2MHz and 2.5MHz for improved EMI performance.
The LT3942 has an operating input voltage range of 3V
to 36V. It has internal, synchronous 40V switches for
high efficiency and small size. It has an adjustable switch-
ing frequency between 300kHz and 2MHz. The LT3942
can by synchronized to an external oscillator source,
programmed with SSFM enabled for low EMI, or set to
normal operation.
The board is designed with ceramic capacitors placed
near the PVIN and PVOUT pins to form a compact high
frequency hotloop. SMD pads are available to install an
optional ferrite bead EMI filter on both the input and
output of DC3103A. Small cuts on the top layer copper
between the SMD pads of both ferrite bead components
are necessary to install the EMI filter correctly. These
All registered trademarks and trademarks are the property of their respective owners.
filters, combined with proper board layout and SSFM,
are effective in reducing both radiated and conducted EMI.
Please follow the recommended layout and four-layer PCB
thickness of DC3103A for low EMI applications.
DC3103A uses the LT3942’s voltage regulation loop to
program a constant-voltage output of 12V. The LT3942
can operate as a constant voltage regulator as well as
a constant current regulator. For LED driver designs,
please refer to demonstration circuit DC2404A. DC2404A
includes a high-side PMOS disconnect switch to assist
with PWM dimming, as well as several other optimizations
for LED driver applications.
The LT3942 datasheet gives a complete description of the
part, operation, and applications information. The data-
sheet must be read in conjunction with this User Guide
for DC3103A. The LT3942EUFD is assembled in a 28-lead
plastic QFN (UFD) package with a thermally-enhanced
exposed ground pad. Proper board layout is essential for
maximum thermal and low-noise performance. Refer to
DC3103A’s design files files for recommended layout and
routing of the LT3942 for voltage regulator applications.
Design files for this circuit board are available.

2
DEMO MANUAL DC3103A
Rev. 0
QUICK START PROCEDURE
Demonstration circuit DC3103A is easy to set up to evaluate
the performance of the LT3942. Follow the procedure below.
1. With power off, connect a load capable of 12V 1A
operation between the VOUT and GND turrets on the
PCB as shown in Figure1.
2. Connect the EN/UVLO turret to GND.
3. Set JP1 to NO SSFM/SYNC to run without SSFM.
4. With power off, connect an input power supply to the
PV
IN
and GND turrets. Make sure that the DC input
voltage will not exceed 40V.
5. Turn the input power supply on and adjust the voltage
between 7V and 36V for full output power capability
and accurate 12V output regulation. Below 7V, output
power capability is reduced.
6. Release the EN/UVLO-to-GND connection.
7. Observe the load running at the programmed output
voltage.
8. To enable spread spectrum frequency modulation, set
JP1 to SSFM ON.
PERFORMANCE SUMMARY
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage PVIN Range Operating 3 36 V
Input Voltage PVIN Range (Full Power) VOUT = 12V, IOUT = 1A 7 36 V
Switching Frequency (fSW) R4 = 14.3kΩ, JP1 = NO SSFM/SYNC 2.0 MHz
Spread Spectrum (SSFM) Range R4 = 14.3kΩ, JP1 = SSFM 2.0 2.5 MHz
Output Voltage VOUT R2 = 110kΩ, R3 = 10kΩ 12 V
Typical Efficiency PVIN = 12V, VOUT = 12V, IOUT = 1A, fSW = 2MHz
JP1 = NO SSFM/SYNC
89 %
Peak Switch Current Limit 2.2 2.5 2.8 A
PVIN Undervoltage Lockout (UVLO) Falling R7 = 402kΩ, R12 = 324kΩ 3.0 V
PVIN Enable Turn-On (EN) Rising R7 = 402kΩ, R12 = 324kΩ 4.0 V
PVIN Quiescent Current VEN/UVLO = 0.3V, VOUT = 12V
VEN/UVLO = 1.3V, VOUT = 12V, Not Switching
0.9
2.6
2
4
µA
mA
Figure1. . Test Procedure Setup Drawing for DC3103A

3
DEMO MANUAL DC3103A
Rev. 0
QUICK START PROCEDURE
Figure2. DC3103A Efficiency vs Input Voltage, SSFM OFF Figure3. DC3103A Efficiency vs Load Current, SSFM OFF
Figure4. DC3103A 10% to 100% Load Step Transient Figure5. DC3103A Output Ripple (20MHz Bandwidth Limit)
Figure6. DC3103A Thermal Image, 10 Minute Runtime, 23°C
Ambient PVIN = 12V, VOUT = 12V, IOUT = 1A, SSFM OFF
V
OUT
= 12V
I
OUT
= 1A
I
OUT
= 0.5A
PV
IN
(V)
0
5
10
15
20
25
30
35
40
50
55
60
65
70
75
80
85
90
95
100
EFFICIENCY (%)
Efficiency vs Input Voltage
DC3103A
V
OUT
= 12V
9PV
IN
12PV
IN
24PV
IN
36PV
IN
I
OUT
(A)
0.01
0.1
1
30
40
50
60
70
80
90
100
EFFICIENCY (%)
Efficiency vs Load Current
DC3103A
Output Transient Response
DC3103A
100mA
1A
V
OUT
= 12V
PV
IN
= 12V
200µs/DIV
V
OUT(AC)
100mV/DIV
I
OUT
500mA/DIV
Output Ripple (V
OUT
= 12V I
OUT
=1A)
DC3103A
9PV
IN
12PV
IN
24PV
IN
36PV
IN
200ns/DIV
V
OUT(AC)
50mV/DIV

4
DEMO MANUAL DC3103A
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 CAP., 10uF, X5R, 50V, 10%, 1206 TAIYO YUDEN, UMK316BBJ106KL-T
2 1 C2 CAP., 0.47uF, X5R, 50V, 10%, 0402 MURATA, GRM155R61H474KE11D
3 1 C3 CAP., 2.2uF, X5R, 6.3V, 10%, 0402 AVX, 04026D225KAT2A
4 3 C4, C8, C9 CAP., 0.1uF, X7R, 10V, 10%, 0402 AVX, 0402ZC104KAT2A
5 1 C5 CAP., 0.22uF, X7R, 6.3V, 10%, 0402 KEMET, C0402C224K9RACTU
6 1 C6 CAP., 470pF, C0G, 50V, 5%, 0402, AEC-Q200 TDK, CGA2B2C0G1H471J050BA
7 1 C7 CAP., 10uF, X7R, 25V, 10%, 1206 AVX, 12063C106KAT2A
8 1 C18 CAP., 68uF, ALUM POLY HYB, 25V, 20%, 6.3x5.8mm,
SMD, RADIAL, AEC-Q200
PANASONIC, EEHZK1E680P
9 1 L1 IND., 3.3uH, WE-MAPI, 20%, 2.2A, 114mOHMS,
3020
WURTH ELEKTRONIK, 74438336033
10 1 R2 RES., 110k OHMS, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402110KFKED
11 1 R3 RES., 10k OHMS, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210K0JNED
12 1 R4 RES., 14.3k OHMS, 1%, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2RKF1432X
13 1 R5 RES., 68k OHMS, 5%, 1/16W, 0402 VISHAY, CRCW040268K0JNED
14 1 R7 RES., 402k OHMS, 1%, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2RKF4023X
15 1 R9 RES., 100k OHMS, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402100KJNED
16 1 R10 RES., 34.8k OHMS, 1%, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2RKF3482X
17 1 R11 RES., 1M OHM, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW04021M00JNED
18 1 R12 RES., 324k OHMS, 1%, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2RKF3243X
19 1 U1 IC, 36V, 2A SYNC. BUCK-BOOST CVRTR, QFN-28, ANALOG DEVICES, LT3942EUFD#PBF
Additional Demo Board Circuit Components
1 1 C10 CAP., 22uF, ALUM POLY HYB, 50V, 20%, 6.3x5.8mm,
SMD, RADIAL, AEC-Q200
PANASONIC, EEHZC1H220P
2 0 C11, C19 CAP., OPTION, ALUM. ELECT., SMD
3 0 C13, C15, C16, C20 CAP., OPTION, 0402
4 0 C14 CAP., OPTION, 1206
5 0 FB1, FB2 IND., FERRITE BEAD, OPT, 0805
6 0 R1, R20, R23 RES., OPTION, 0805
7 0 R15, R16, R17, R24, R25 RES., OPTION, 0402
8 2 R18, R19 RES., 0 OHM, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2GE0R00X
9 1 R22 RES., 0 OHM, 1/16W, 0402, AEC-Q200 VISHAY, CRCW04020000Z0ED
10 1 R13 RES., 100k OHMS, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402100KJNED
Hardware: For Demo Board Only
1 4 E1, E4, E7, E8 TEST POINT, TURRET, 0.064" MTG. HOLE, PCB
0.062" THK
MILL-MAX, 2308-2-00-80-00-00-07-0
2 4 E2, E3, E10, E11 TEST POINT, TURRET, 0.094" MTG. HOLE, PCB
0.062" THK
MILL-MAX, 2501-2-00-80-00-00-07-0
3 1 JP1 CONN., HDR, MALE, 2x3, 2mm, VERT, ST, THT WURTH ELEKTRONIK, 62000621121
4 1 XJP1 CONN., SHUNT, FEMALE, 2 POS, 2mm WURTH ELEKTRONIK, 60800213421

5
DEMO MANUAL DC3103A
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
SCHEMATIC DIAGRAM
5
5
4
4
3
3
2
2
1
1
D D C C B B A A
1. ALL RESISTORS ARE 0402 5%. ALL CAPACITORS ARE 0402.
NOTE: UNLESS OTHERWISE SPECIFIED
2MHz
SEE USER GUIDE
*
*
INTVCC
VREF
INTVCC
VIN
INTVCC
DATE:
SHEET OF
TITLE: SCHEMATIC
SIZE:
SCHEMATIC NO. AND REVISION:
CUSTOMER NOTICE
THIS CIRCUIT IS PROPRIETARY TO ANALOG DEVICES AND
SUPPLIED FOR USE WITH ANALOG DEVICES PARTS.
www.analog.com
SKU NO.
IC NO.
ANALOG DEVICES 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 ANALOG DEVICES APPLICATIONS ENGINEERING FOR ASSISTANCE.
11
36V 4-SWITCH BUCK-BOOST VOLTAGE REGULATOR
710-DC3103A_REV02
N/A
LT3942EUFD DC3103A
Monday, February 01, 2021
<VariantName>
DATE:
SHEET OF
TITLE: SCHEMATIC
SIZE:
SCHEMATIC NO. AND REVISION:
CUSTOMER NOTICE
THIS CIRCUIT IS PROPRIETARY TO ANALOG DEVICES AND
SUPPLIED FOR USE WITH ANALOG DEVICES PARTS.
www.analog.com
SKU NO.
IC NO.
ANALOG DEVICES 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 ANALOG DEVICES APPLICATIONS ENGINEERING FOR ASSISTANCE.
11
36V 4-SWITCH BUCK-BOOST VOLTAGE REGULATOR
710-DC3103A_REV02
N/A
LT3942EUFD DC3103A
Monday, February 01, 2021
<VariantName>
DATE:
SHEET OF
TITLE: SCHEMATIC
SIZE:
SCHEMATIC NO. AND REVISION:
CUSTOMER NOTICE
THIS CIRCUIT IS PROPRIETARY TO ANALOG DEVICES AND
SUPPLIED FOR USE WITH ANALOG DEVICES PARTS.
www.analog.com
SKU NO.
IC NO.
ANALOG DEVICES 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 ANALOG DEVICES APPLICATIONS ENGINEERING FOR ASSISTANCE.
11
36V 4-SWITCH BUCK-BOOST VOLTAGE REGULATOR
710-DC3103A_REV02
N/A
LT3942EUFD DC3103A
Monday, February 01, 2021
<VariantName>
C9
0.1uF
10V
FB1
OPT
0805
LT3942EUFD
U1
VIN
3
PVIN
1
PVIN
2
EN/UVLO
5
OVLO
6
INTVCC
4
FAULT
14
SS
15
VREF
9
CTRL
10
PWM
8
RP
7
PVOUT 22 PVOUT 21
ISP 11
ISN 12
FB 16
PWMTG 20
ISMON 13
VC 17 RT 18
SYNC/SPRD 19
BST1 26
SW1 27
SW1 28
SW2 23
SW2 24
BST2 25
GND
29
C20 OPT
R24 OPT
E1
VIN
R9
100k
E8 SYNC
R4 14.3k
TP3 ISMON
C3
2.2uF R13
100k
+
C11 OPT
JP1
SSFM
EXT SYNC
NO SSFM/SYNC
SYNC/SPRD
1 3 5 6
4 2
E7
GND
+
C19 OPT
C14 OPT 1206
C13 OPT
R1
OPT
0805
TP1
FAULT _____
R7 402k
TP2 LOOP INJ
R17
OPT
C15 OPT
E2
GND
R16
OPT
R15
OPT
E10 GND
R10
34.8k
C16 OPT
R11 1M
R18 0
R3
10k
R22 0
R23 OPT 0805
R12
324k
C5
0.22uF
R19 0
C4
0.1uF
C1 10uF 50V 1206
L1
3.3uH
74438336033
E3
3V - 36V
PVIN
C6 470pF
C2 0.47uF 50V C7
10uF 1206 25V
+
C10 22uF 50V
EEHZC1H220P
E11 VOUT
12V 1A
FB2
OPT
0805
R25 OPT
R5 68k
R20 OPT 0805
R2 110K
E4
EN/UVLO
C8
0.1uF
10V
+
C18 68uF
EEHZK1E680P
25V
ISN
ISP
ISN
ISP

6
DEMO MANUAL DC3103A
Rev. 0
 ANALOG DEVICES, INC. 2021
06/21
www.analog.com
ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection
circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.
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