Linear Technology LT3790 Quick setup guide

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dc2123bfa
DEMO MANUAL DC2123B
DESCRIPTION
LT3790
60V Four-Switch Synchronous
Buck-Boost Controller
TheDC2123Bisa60Vfour-switchsynchronousbuck-boost
controller that demonstrates the high power capability
of the LT
®
3790. The output is 24V and the maximum
output current is 5A. The switching frequency is 200kHz
and efficiency is as high as 98% for a 24V input.
The LT3790 is capable of high power operation. DC2123B
can be altered for increased output power with higher
minimum input voltage. If VIN remains always above
20V, IOUT can be increased to 12A+ (for 290W output) by
changing RS2 to 4mΩ.
The operating input voltage range of DC2123B is from 8V
to 56V. The output voltage, EN/UVLO, and OVLO are all
programmed by resistor dividers. EN/UVLO is set so the
circuit will turn off when the input voltage falls below 8V
and will turn on when the input voltage rises above 9.6V.
OVLO is set to engage for input voltages above 57V.
Current sense resistors program input and output current
limits and also determine the monitoring voltages that
indicate input and output current. IVINMON provides a
30mV/1A voltage that is used to monitor the input cur-
rent. Input current limit occurs at 33.3A and is set by
RIN1. ISMON provides a 160mV/1A voltage that is used
to monitor the output current. The output current limit is
7.5A and is set by RS2.
The demo circuit features MOSFETs that compliment the
5V gate drive of the LT3790 to achieve high efficiency. 60V
MOSFETs are used on the input side of the four-switch
topology while 40V MOSFETs are used on the output side.
Ceramic capacitors are used at both the circuit input and
output because of their small size and high ripple current
capability. In addition to ceramic capacitors, there is an
aluminum polymer capacitor on the output that assures
feedback loop stability, even at low temperatures. The
input has an aluminum electrolytic capacitor in addition
to ceramic capacitors. A two-stage L-C input filter can
easily be added for electro-magnetic compatibility. The
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
pcb has large copper planes and extensive vias for thermal
performance.
The CLKOUT output and the SYNC input can be used to
synchronize switching between two or more DC2123B
circuits. A resistor from SYNC to ground must be removed
prior to using the SYNC input.
SHORT and C/10 are open-collector statusflag outputs and
are pulled up to the INTVCC pin voltage. A resistor shorts
the CCM pin to C/10 and causes the circuit to change to
discontinuousconductionmode (DCM)when C/10 isactive
at light load currents. CCM can also be connected with a
resistor to INTVCC instead of C/10 for continuous conduc-
tion mode (CCM) operation over the entire load range.
The CTRL input is pulled up to the VREF pin through a 0Ω
resistor to set the output current limit to its maximum,
and an external voltage on CTRL can be used to lower the
current limit if the resistor is removed. A capacitor at the
SS pin programs soft-start and additionally SS is pulled
up to the VREF pin through a 100k resistor. The switching
frequency is adjustable with a resistor.
The demo circuit is designed to be easily reconfigured to
many other applications, including the example schemat-
ics in the data sheet. Consult the factory for assistance.
High power operation, four-switch buck-boost topology,
fault protection and full monitoring make the LT3790
attractive for high power voltage regulator circuits and
also circuits that require output current regulation such
as battery chargers. The LT3790EFE is available in a
thermally enhanced 38-lead TSSOP package. The LT3790
data sheet must be read in conjunction with this demo
manual to properly use or modify demo circuit DC2123B.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2123B

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DEMO MANUAL DC2123B
QUICK START PROCEDURE
It is easy to set up demonstration circuit DC2123B to
evaluate the performance of the LT3790. Refer to Figure1
for the proper measurement equipment setup and follow
the procedure below:
NOTE: Make sure that the voltage applied to PVIN does
not exceed the absolute maximum voltage rating of 60V
for the LT3790.
1. Connect the EN/UVLO terminal to ground with a clip-on
lead. Connect the power supply (with power off), load,
and meters as shown.
2. After all connections are made, turn on the input power
and verify that the input voltage is between 8V and56V.
3. Remove the clip-on lead from EN/UVLO. Verify that the
output voltage is 24V.
NOTE: If the output voltage is low, temporarily disconnect
the load to make sure that it is not set too high.
4. Once the proper output voltage is established, adjust
the input voltage and load within the operating ranges
and observe the output voltage regulation, ripple volt-
age, efficiency and other parameters.
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage, VPVIN VOUT = 24V IOUT ≤ 5A 8 V
Maximum Input Voltage, VPVIN VOUT = 24V IOUT ≤ 5A 56 V
Maximum Output Current 8V < VPVIN < 56V, CTRL = VREF 5 A
Input EN Voltage, VPVIN(EN) R3 = 88.7k, R4 = 499k, VPVIN Rising 9.6 V
Input UVLO Voltage, VPVIN(UVLO) R3 = 88.7k, R4 = 499k, VPVIN Falling 8.0 V
Input OVLO Turn-Off Voltage, VPVIN(OVLO turn-off) R11 = 27.4k, R1 = 499k, VPVIN Rising 57.6 V
Input OVLO Turn-On Voltage, VPVIN(OVLO turn-on) R11 = 27.4k, R1 = 499k, VPVIN Falling 56.2 V
Output Voltage VOUT R19 = 71.5k, R34 = 1.37k, R20 = 3.83k 23.5 24.5 V
Efficiency VPVIN = 24V, IOUT = 5A 98 %
Switching Frequency R18 = 147k 200 kHz
Input Current Limit RIN1 = 0.0015Ω 33 A
Output Current Limit RS2 = 0.008Ω 7.5 A

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DEMO MANUAL DC2123B
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup for DC2123B
Figure 2. Efficiency
V
IN
= 12V
V
IN
= 24V
LOAD CURRENT (A)
0
1
2
3
4
5
80
85
90
95
100
EFFICIENCY (%)
dc2123 F02

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DEMO MANUAL DC2123B
QUICK START PROCEDURE
Figure 3. Output Voltage Ripple at 5A Output Current, VOUT = 24V, 25MHz Bandwidth
Figure 4. Output Voltage Load Transient Response, VOUT = 24V, IOUT = 2.5A to 5A to 2.5A, 25MHz Bandwidth
VIN = 14V
VIN = 24V
VIN = 54V
VIN = 14V
VIN = 24V
VIN = 54V

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DEMO MANUAL DC2123B
QUICK START PROCEDURE
Figure 5. VOUT in Current Limit, VIN = 24V
IOUT (A)
0
0
VOUT (V)
5
15
10
25
20
30
1 2 3 4 5 6 87
dc2009a F05
The LT3790 is an improved version of the LT3791-1 and
is recommended for use in new designs. Some external
componentvalues may change, but otherwise, the LT3790
is functionally equivalent to the LT3791-1. The differences
between the two products are:
1. The LT3790 has a 60mV (typical) full-scale V(ISP-ISN)
current sense voltage, compared to 100mV (typical) for
the LT3791-1. This change allows lower power current
sense resistors to be used for most applications.
2. The LT3790 CTRL pin linear range is from 0V to 1.1V,
andhasaturn-offthresholdof 50mV(typical),compared
to a 200mV to 1.1V linear range and 175mV (typical)
turn-off threshold for the LT3791-1. These changes
make it easier to parallel two or more LT3790 ICs for
higher power levels.
3. TheLT3790C/10pinpullslowwhentheV(ISP-ISN)
voltage
is less than 1/10 full scale, compared to the LT3791-1,
where C/10 pulls low when both V(ISP-ISN) is less than
1/10 full scale and VFB is greater than 1.15V(typical).
Since the C/10 pin is used to allow DCM mode for some
applications, this change ensures that negative current
does not occur at light loads for a broader range of
applications.
DIFFERENCES BETWEEN LT3790 AND LT3791-1

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DEMO MANUAL DC2123B
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 CC1, CSS1 CAP., X7R 33nF 25V 10% 0603 AVX 06033C333KAT1A
2 1 C1 CAP., X5R 0.47µF 16V 20% 0402 TDK C1005X5R1C474MT
3 3 C2, C12, C13 CAP., X5R 0.1µF 16V 10% 0402 TDK C1005X5R1C104KT
4 1 C3 CAP., X5R 1µF 100V 10% 1206 TAIYO YUDEN HMK316BJ105KL-T
5 1 C4 CAP., X5R 4.7µF 10V 10% 0603 TAIYO YUDEN LMK107BJ475KA
6 2 C6, C7 CAP., X7S 4.7µF 100V 10% 1210 TDK C3225X7S2A475K200AB
7 2 C10, C11 CAP., ALUM. ELECT. 47µF 80V ± 20% UNITED CHEMI-CON EMZA800ADA470MJA0G
8 2 C14, C15 CAP., X5R 4.7µF 50V 20% 1210 TAIYO YUDEN UMK325BJ475MM-T
9 2 C20, C30 CAP., HYBRID COND. POLYMER 220µF 35V 20% SUN ELECTRONIC INDUSTRIES 35HVP220M
10 1 C29 CAP., X7R 0.033µF 16V 10% 0402 TDK C1005X7R1C333K
11 2 D1, D2 SCHOTTKY BARRIER 100V SOD323(SC-90) NXP SEMI. BAT46WJ
12 1 L1 INDUCTOR, 10µH SER2900 COILCRAFT, SER2918H-103KL
13 2 M1, M2 MOSFET-N CHANNEL, 60V, TDSON-8 INFINEON, BSC100N06LS3 G
14 2 M3, M4 MOSFET-N CHANNEL, 40V, TDSON-8 INFINEON, BSC032N04LS
15 1 RC1 RES., CHIP 7.5k 0.06W 5% 0402 VISHAY CRCW04027K50JNED
16 1 RIN1 RES., 0.0015Ω 1W 1% 2512 PANASONIC, ERJ-M1WTF1M5U
17 1 RS1 RES., 0.002Ω 1W 1% 2512 PANASONIC, ERJ-M1WTF2M0U
18 1 RS2 RES., 0.008Ω 1W 1% 2512 PANASONIC, ERJ-M1WSF8M0U
19 2 R1, R4 RES., CHIP 499k 0.06W 1% 0603 VISHAY CRCW0603499KFKEA
20 1 R3 RES., CHIP 88.7k 0.06W 1% 0402 VISHAY CRCW040288K7FKED
21 1 R5 RES., CHIP 51Ω 0.06W 5% 0402 NIC, NRC04F51R0TRF
22 2 R6, R10 RES., CHIP 200k 0.06W 5% 0603 VISHAY CRCW0603200KJNEA
23 1 R11 RES., CHIP 27.4k 0.06W 1% 0402 VISHAY CRCW040227K4FKED
24 1 R16 RES., CHIP 200k 0.06W 5% 0402 VISHAY CRCW0402200KJNED
25 1 R17 RES., CHIP 100k 0.06W 5% 0402 VISHAY CRCW0402100KJNED
26 1 R18 RES., CHIP 147k 0.06W 1% 0402 VISHAY CRCW0402147KFKED
27 1 R19 RES., CHIP 71.5k 0.06W 1% 0603 VISHAY CRCW060371K5FKEA
28 1 R20 RES., CHIP 3.83k 0.06W 1% 0402 VISHAY CRCW04023K83FKED
29 1 U1 I.C., 60V BUCK-BOOST VOLT. REG. LINEAR TECH. CORP. LT3790EFE#PBF

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DEMO MANUAL DC2123B
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Additional Demo Board Circuit Components
1 0 C5, C8, C9, C16, C17, C18 (Opt) CAP., 1210
2 0 C19 (Opt) OPTIONAL
3 0 C21, C22, C28, CC2 CAP., 0603
4 0 C23 OPTIONAL
5 0 C24, C25, C26, C27 (Opt) OPTIONAL
6 0 D3, D4 (Opt) SCHOTTKY DIODE, SMB
7 0 D5, D6 (Opt) DIODE, SOD-123
8 0 D7 (Opt) DIODE, SOD-523
9 0 L2, L3 (Opt) OPTIONAL
10 0 M5, M6, M7, M8, M12 (Opt) OPTIONAL
11 0 M9, M10, M11 (Opt) OPTIONAL
12 0 R2, R23, R24, R26-R32 RES., 0603 OPTIONAL
13 1 R7 RES., CHIP 0Ω 1206 YAGEO, RC1206FR-070RL
14 0 R8, R9, R25 Res., 0402 OPTIONAL
15 3 R12, R14, R22 RES., CHIP 0Ω 0402 VISHAY CRCW04020000Z0ED
16 2 R13, R21 RES., CHIP 0Ω 0603 VISHAY CRCW06030000Z0EA
17 1 R34 RES., CHIP 1.37k 0.06W 1% 0603 PANASONIC ERJ-3EKF1371V
Hardware: For Demo Board Only
1 4 E1, E2, E19, E20 CONNECTOR, BANANA JACK KEYSTONE 575-4
2 13 E3, E5, E6, E7, E8, E9, E10, E11, E12,
E13, E14, E21, E22
TURRET, TESTPOINT MILL MAX 2308-2-00-80-00-00-07-0
3 5 E4, E15, E16, E17, E24 TURRET, TESTPOINT MILL MAX 2501-2-00-80-00-00-07-0
4 0 E18 (Opt) OPTIONAL
5 0 E23 (Opt) OPTIONAL
6 4 MH1-MH4 STANDOFF, NYLON 0.50" KEYSTONE, 8833 (SNAP-ON)

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DEMO MANUAL DC2123B
SCHEMATIC DIAGRAM
NOTE: UNLESS OTHERWISE SPECIFIED. ALL CAPACITORS 0603. ALL RESISTORS 0402 1%.
FB
PWMOUT
SNSP BG1 SW1 TG1 TG2 SW2 BG2 ISP
*C/10
PWM INTVCC
VREF SS *SHORT
INTVCC
INTVCC
VREF
PVIN
INTVCC
VIN
INTVCC
VREF
PVIN VOUT
IVINN
TP6
R11 27.4k
R21
0 Ohm
0603
TP2
M3 BSC032N04LS
R4
499K 0603
M2 BSC100N06LS3
C17 (Opt) 1210
TP4
E7
CTRL
C9 (Opt) 1210
C14 4.7µF 50V 1210
R16
200k
5%
M1 BSC100N06LS3
R10 200k 0603 5%
R8 (Opt)
C8 (Opt) 1210
E8
SHORT
E13
SYNC
R1 499k 0603
+
C30
220µF 35V
C21
(Opt)
D3
(Opt)
SMB
C4 4.7µF
10V
C18 (Opt) 1210
C15 4.7µF 50V 1210
R17
100k
5%
U1 LT3790EFE
EN/UVLO
9
SHORT
5
C/10
4
IVINN
11
CTRL
1
PWM
3
ISP
25
SYNC
34
SS
2
PWMOUT
31
VC
36
RT
35
IVINMON
8
ISMON
7
IVINP
10
CLKOUT
33
VREF
6
OVLO
38
SNSN
28
SNSP
27
ISN
26
PGND
17
PGND
20
FB
37
TG2
24
SW2
21
BG2
19
BG1
18
SW1
16
TG1
14
BST1
15
BST2
22
CCM
32
VIN
12
INTVCC
13
SGND
30
SGND
39
TEST1
29
E20
GND
CSS1 33nF
R12 0 Ohm
+
C20
220µF 35V
E12
CLKOUT
RS1 0.002 1% 2512
+
C19 (Opt) 12.5mmDia. Thru‐Hole
E9
C/10
R34
1.37k 0603
CC1 33nF
R3 88.7k
C5 (Opt) 1210
L1
10µH
SER2918H-103KL
12
3
C7 4.7uF 100V 1210
E1
PVIN
8V - 56V
E16
GND
E10
IVINMON
C12 0.1µF 0402
R13 0 Ohm 0603
R6 200k 0603 5%
TP5
E2
GND
C2 0.1µF 0402
C1
0.47µF
0402
E15
GND
TP3
E5
EN/UVLO
R14 0 Ohm
E14
GND
E18
OUT
(Opt)
+
C11 47µF 80V
R20
3.83k
C6 4.7uF 100V 1210
+
C10 47µF 80V
M4
BSC032N04LS
RS2
0.008
2512
E3
VIN
8V - 56V
R19
71.5k 0603
C13 0.1µF 0402
C29 0.033µF 0402
R22 0 Ohm
E6
OVLO
C3 1µF 100V 1206
RIN1
0.0015
1%
2512
D2 BAT46WJ
RC1
7.5k
5%
R9
(Opt)
C16 (Opt) 1210
R18 147k 200kHz
E4
GND
R2 (Opt) 0603
CC2 OPT
E11
ISMON
E19 VOUT
24V 5A
D4
(Opt)
SMB
R5
51
5%
D1 BAT46WJ
TP1
R7 0 Ohm 1206
E17
GND
SNSP
ISP
SW2 FB
PWMOUT PWMSS
*SHORT
TG2 BG2
BG1
TG1 SW1
*C/10

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DEMO MANUAL DC2123B
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
SW2
BG2
ISP
FB
PWMOUT
SNSP
BG1
SW1
TG1 TG2
*C/10
INTVCC
PWM
*SHORT
VREF
SS
VIN IVINN
IVINN
PVIN PVINPVIN
VREF
VREF
R32 (Opt) 0603
E22
INTVCC
R29
(Opt)
0603
E24
GND
+
C23 47µF 80V
(Opt)
10mm Dia. Surface Mount
R30
(Opt)
0603
M10 SOT-23 (Opt)
L3
4.7µH
7443551470
Wurth Electronik
(Opt)
R24
(Opt)
0603
C24 4.7µF 100V 1210 (Opt)
D5
(Opt)
SOD-123
M9
SOT-23
(Opt)
M7 (Opt) PG-TDSON-8
L2
4.7µH
7443551470
Wurth Electronik
(Opt)
E21
PWM
M6 (Opt) PG-TDSON-8
C22 (Opt)
M11 SOT-23 (Opt)
D6
(Opt)
SOD-123
C25 4.7µF 100V 1210 (Opt)
C27 4.7µF 100V 1210 (Opt)
E23
LED-
(Opt)
R28 (Opt) 0603
R31 (Opt) 0603
M12 (Opt) LFPAK
R23
(Opt)
0603
D7
SOD-523
(Opt)
M5 (Opt) PG-TDSON-8
R25 (Opt)
R27 (Opt) 0603
R26 (Opt) 0603
C28 (Opt)
C26 4.7µF 100V 1210 (Opt)
M8 (Opt)
PG-TDSON-8
ISP
SW1 SW2
*C/10
TG1 BG1
TG2 BG2
SW1 SW2 SNSP SNSP
PWMOUT
ISP
INTVCC
PWM
*SHORT
SS
FB
ISP

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DEMO MANUAL DC2123B
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2014
LT 0117 REV A • 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
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:
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Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation