Linear Technology DC1878A Quick setup guide

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DEMO MANUAL DC1878A
Description
LTC3789EGN
8V to 75VIN Buck/Boost
DC/DC Converter
Demonstration circuit 1878A features the LTC3789EGN,
a high efficiency switching step-up/down controller. The
input range has been extended to 75V by using a LTC4444-
5 MOSFET driver on the input side. The minimum input
voltage is 8V. The output voltage is 12V. The board is
capable of delivering up to 5A of output current over the
input voltage range.
The LTC3789EGN is a high performance switching regula-
tor controller designed to regulate the output using input
voltages above, below or equal to the output voltage.
Synchronous operation provides very high efficiency, up
to 97%. Constant frequency current mode architecture
allows phase-lockable frequency from 200kHz to 600kHz. L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
performance summary
An accurate output current limit provides support for bat-
tery charging. A wide input and output range with smooth
transfer function through all operating modes makes the
productidealforautomotive,telecomandbattery systems.
The MODE/PLLIN pin can select between pulse-skipping
mode and forced continuous mode operation and allows
the IC to be synchronized to an external clock. A power
good output pin indicates when the output is within 7.5%
of its set point.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)
PARAMETER CONDITIONS VALUE
Minimum Input Voltage 8V
Maximum Input Voltage 75V
Output Voltage VOUT Regulation VIN = 8V – 75V, IOUT = 0A – 5A 12V ± 2%
Maximum Continuous Output Current Some Airflow May Be Needed at High Input Voltage and
Continuous Full Load
5A
Default Operating Frequency R3 = 0Ω 200kHz
External Clock Synchronous Frequency Range 200kHz – 600kHz
Efficiency VIN = 8V to 75V, IOUT = 5A 90.5% to 97%. See Figures 3 and 6
Load Transient See Figure 5

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DEMO MANUAL DC1878A
Quick start proceDure
Demonstration circuit 1878A is easy to set up to evalu-
ate the performance of the LTC3789EGN. Please refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below.
1. With power off, connect the input supply, load and
meters as shown in Figure 1. Preset the load to 0A and
VIN supply to 0V.
2. Set the current limit of the input supply high enough
so that the bench supply does not go into current limit
mode. Figure 2 shows input current as a function of
input voltage, at full load. Input current can reach 8A
at 8V input voltage.
3. Place jumper in the following position:
JP1
RUN
ON
4. Turn on the power at the input. Increase VIN to between
8V and 75V. The circuit will start and the output voltage
will regulate at 12V ±2%. The current draw at no load is
typically 18mA to 37mA depending on the input voltage.
5. Apply load and observe output voltage regulation, ripple
voltage, efficiency and other parameters. Efficiency and
power loss at full load is shown in Figure 3. Continuous
operation with full power and high input voltage may
require some airflow.
Auxiliary Supply
The demo board DC1878A has a LTC3803 based flyback
converter to provide 8V/50mA bias voltage for LTC3789
and LTC4444-5. The snubber for the flyback primary wind-
ing provides a voltage that is above the input voltage. A
transistor Q9 is used to provide a small current source
to the top gate driver of LTC4444-5 so that 100% duty
cycle is possible.
If this current source is not used, for example if the flyback
auxiliary supply is replaced by an external 6V to 12Vsupply,
it is necessary to connect BOOST1 to 3.0V (add 3V Zener
diode D11, R11 = 1k, remove R16) and use a level shift
circuit (add D3 = BAS16, R12 = 1k, remove R6) between
TG1 and TINP (due to the 3.25V maximum threshold for
TINP). By setting BOOST1 to 3.0V, the LTC3789 will issue
narrow refresh pulses on BG1 which keeps the top gate
driver powered also in BOOST mode.
In addition, DC1878Ademoboard has layoutfor an optional
bias supply intended for a future monolithic high voltage
buck regulator. Additional information will be provided
when this part is released.

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DEMO MANUAL DC1878A
Figure 1. Proper Measurement Equipment Setup
Quick start proceDure

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DEMO MANUAL DC1878A
Quick start proceDure
Figure 2. Input Current at Full Load (12V at 5A Output)
Figure 3. Efficiency and Power Loss at Full Load. The Power Loss is Highest at High Input
Voltage Due to the Switching Losses and Drops as Input Voltage Decreases, Until the Inductor
Current Starts to Increase as the Circuit Enters Boost Mode Below 10V Input Voltage
INPUT VOLTAGE (V)
40302010 807060500
EFFICIENCY (%)
POWER LOSS (W)
100
98
94
96
92
90
86
88
84
8
7
5
6
4
3
1
2
0
PLOSS
η%
INPUT VOLTAGE (V)
40302010 807060500
CURRENT (A)
10
9
7
8
6
5
3
4
2
1
IOUT
0
IIN

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DEMO MANUAL DC1878A
Quick start proceDure
Figure 4. Output Ripple Voltage Measured Across COUT1
100mV

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DEMO MANUAL DC1878A
Quick start proceDure
Figure 5. Load Transient Response

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DEMO MANUAL DC1878A
Quick start proceDure
Figure 6. Efficiency at Various Input Voltages
LOAD (A)
4321 50
EFFICIENCY (%)
100
98
94
96
92
90
88
85
86
99
95
97
93
91
89
87
8V
12V
16V
24V
36V
48V
60V
72V
76V

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DEMO MANUAL DC1878A
Figure 7. Output Current Limit (The Easiest Way to
Do This Test Is with an Active Load in Voltage Mode)
Quick start proceDure
LOAD (A)
4321 650
VOUT (V)
14
12
8
10
6
4
2
0

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DEMO MANUAL DC1878A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
1 1 CC1 CAP, 0603 470pF 10% 50V NPO AVX 06035A471KAT
2 1 CC2 CAP, 0603 0.01µF 10% 50V X7R AVX 06035C103KAT2A
3 0 CF1, C31, C32, C37, CF CAP, 0603 OPTION OPTION
4 0 CIN1, COUT11, CIN11, COUT21, CIN21 CAP, OPTION OPTION
5 1 CIN2 CAP, 150µF 100V ELEC SUN ELEC. 100ME150AX
6 1 COUT1 CAP, 330µF 20% 16V OSCON SUN ELECT. 16SEP330M+T
7 0 COUT2 CAP, 330µF 20% 16V OSCON OPTION SUN ELECT. 16SEP330M+T OPTION
8 1 CSS CAP, 0603 4700pF 10% 50V X7R AVX 06035C472KAT2A
9 2 C1,C2 CAP, 1210 22µF 10% 25V X5R MURATA GRM32ER61E226KE15L
10 0 C3, C21, C23, C25, C27, C28 CAP, 1210 OPTION OPTION
11 1 C4 CAP, 0603 0.22µF 10% 25V X7R AVX 06033C224KAT2A
12 3 C5, C6, C9 CAP, 1210 2.2µF 10% 100V X7R MURATA GRM32ER72A225KA35L
13 0 C7, C8, C29, C30, C33 CAP, 1210 2.2µF 10% 100V X7R OPTION MURATA GRM32ER72A225KA35L OPTION
14 1 C10 CAP, 0603 4.7µF 20% 6.3V X5R TAIYO YUDEN JMK 107 BJ457MA-T
15 1 C11 CAP, 0603 33pF 10% 50V NPO AVX 06035A330KAT2A
16 0 C12, C13 CAP, 1206 OPTION OPTION
17 3 C14, C16, C26 CAP, 0603 0.1µF 10% 50V X7R AVX 06035C104KAT2A
18 1 C15 CAP, 0805 1µF 20% 16V X5R AVX 0805YD105MAT2A
19 1 C17 CAP, 0603 1nF 10% 50V COG AVX 06035A102KAT2A
20 2 C18, C20 CAP, 1206 10µF 20% 10V X7R AVX 1206ZC106MAT2A
21 2 C19, C24 CAP, 0603 1µF 20% 16V X7R AVX 0603YC105MAT2A
22 1 C22 CAP, 0603 0.22µF 20% 16V X7R TAIYO YUDEN EMK107BJ224MA
23 0 C34 CAP, 0603 0.1µF 10% 50V X7R OPTION AVX 06035C104KAT2A OPTION
24 0 C35 CAP, 0603 47nF 10% 25V X7R OPTION AVX 06033C473KAT2A OPTION
25 0 C36 CAP, 1210 47µF 10% 10V X7R OPTION MURATA GRM32ER71A476KE15L OPTION
26 3 D2, D9, D12 DIODE, SWITCHING, 200mW, SOT23 DIODES INC. BAS16
27 0 D3, D10, D11 DIODE, OPTION SOT-23 OPTION
28 2 D4, D14 DIODE, SWITCHING, 350mW, SOT23 DIODES INC. BAS21
29 1 D5 DIODE, SCHOTTKY DIODES INC. B1100
30 1 D6 DIODE, SCHOTTKY, SMA DIODES INC. B240A-13-F
31 1 D7 DIODE, SCHOTTKY DIODES INC. DFLS160
32 1 D8 DIODE, ZENER, 5.1V, SOT23 DIODES INC. BZX84C5V1-7-F
33 1 D13 DIODE, ZENER, 6.8V, SOT23 DIODES INC. BZX84C6V8
34 1 D15 DIODE, 1.0A HIGH VOLTAGE SCHOTTKY
BARRIER RECTIFIER
DIODES INC. DFLS1100
35 1 JP1 HEADER, SINGLE ROW, 3 PIN, 2mm SAMTEC TMM103-02-L-S
36 0 JP2 HEADER, SINGLE ROW, 3 PIN, 2mm
OPTION
SAMTEC TMM103-02-L-S OPTION
37 4 J1, J2, J3, J4 JACK, BANANA KEYSTONE 575-4
38 1 L1 IND, 19µH PULSE PA2050.193NL
39 0 L2 IND, 22µH OPTION TDK VLF10040T-220M2R5 OPTION
40 4 MH1, MH2, MH3, MH4 STANDOFF, SNAP ON KEYSTONE_8834

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DEMO MANUAL DC1878A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
41 1 Q1 XSTR, FDC2512 N-CHANNEL MOSFET FAIRCHILD FDC2512
42 1 Q2 XSTR, MOSFET N-CHANNEL 100V VISHAY SiR870DP
43 2 Q3, Q5 XSTR, MOSFET N-CHANNEL 20V VISHAY SiR496DP-T1-GE3
44 1 Q4 XSTR, MOSFET N-CHANNEL 100V VISHAY SiR882DP
45 1 Q6 XSTR, SMALL SIGNAL NPN SOT-23 DIODES INC. MMBTA42-7
46 0 Q8, Q13 XSTR, MOSFET N-CHANNEL 20V OPTION VISHAY SiR496DP-T1-GE3 OPTION
47 1 Q9 XSTR, SMALL SIGNAL PNP SOT-23 DIODES INC. MMBTA92-7
48 0 Q14, Q15 XSTR, MOSFET N-CHANNEL 100V OPTION VISHAY SiR882DP OPTION
49 1 RC RES, 0603 14.7kΩ 1% 1/10W VISHAY CRCW060314K7FKEA
50 1 RFB1 RES, 0603 113kΩ 1% 1/10W VISHAY CRCW0603113KFKEA
51 1 RFB2 RES, 0603 8.06kΩ 1% 1/10W VISHAY CRCW06038K06FKEA
52 1 R1 RES, 0805 5.6Ω 1% 1/10W VISHAY CRCW08055R60FKNEA
53 1 R2 RES, 3720 0.01Ω 2% 1W THIN FILM RECH. RL3720WT-R010-F
54 3 R3, R4, R44 RES, 0603 100Ω 5% 1/10W VISHAY CRCW0603100RJNEA
55 1 R5 RES, 0805 4.7Ω 1% 1/10W VISHAY CRCW08054R70FKNEA
56 8 R6, R11, R16, R21, R25, R27, R32, R50 RES, 0603 0Ω JUMPER VISHAY CRCW06030000Z0EA
57 3 R7, R15, R20 RES, 0603 100kΩ 1% 1/10W VISHAY CRCW0603100KFKEA
58 2 R8, R26 RES, 0603 10Ω 5% 1/10W VISHAY CRCW060310R0JNEA
59 2 R9, R10 RES, 0603 1kΩ 1% 1/10W VISHAY CRCW06031K00FKEA
60 0 R12, R19, R22, R23, R33-R36, R51 RES, 0603 OPTION OPTION
61 2 R13, R14 RES, 0603 154kΩ 1% 1/10W VISHAY CRCW0603154KFKEA
62 0 R17 RES, 0805 0Ω JUMPER OPTION VISHAY CRCW08050000Z0EA OPTION
63 1 R18 RES, 3720 0.012Ω 2% 1W THIN FILM TECH. RL3720WT-R012-F
64 1 R24 RES, 0603 10kΩ 1% 1/10W VISHAY CRCW060310K0FKEA
65 0 R28, R29 RES, 1206 OPTION OPTION
66 1 R30 RES, 1206 64.9kΩ 1% 1/10W VISHAY CRCW120664K9FKEA
67 1 R31 RES, 0603 12.1kΩ 1% 1/10W VISHAY CRCW060312K1FKEA
68 1 R37 RES, 0603 14kΩ 1% 1/10W VISHAY CRCW060314K0FKEA
69 1 R38 RES, 1206 220kΩ 5% 1/4W VISHAY CRCW1206220KJNEA
70 1 R39 RES, 1206 100kΩ 1% 1/10W VISHAY CRCW1206100KFKEA
71 1 R40 RES, 0603 22.1kΩ 1% 1/10W YAGEO RC0603FR-0722KIL
72 1 R41 RES, 0603 1.58kΩ 1% 1/10W VISHAY CRCW06031K58FKEA
73 1 R42 RES, 0603 10Ω 1% 1/8W VISHAY CRCW060310R0FKEA
74 1 R43 RES, 1206 0.30Ω 1% 1/8W IRC LR1206LF-01-R300-F
75 1 R45 RES, 0603 24.9kΩ 1% 1/10W NIC NRC06F2492TRF
76 2 R46, R47 RES, 0603 33.2kΩ 1% 1/10W VISHAY CRCW060333K2FKEA
77 1 R48 RES, 0603 5.6kΩ 1% 1/10W VISHAY CRCW06035K49FKEA
78 0 R49, R55, R56 RES, 0603 0Ω JUMPER OPTION VISHAY CRCW06030000Z0EA OPTION
79 0 R52 RES, 0603 2MΩ 1% 1/10W OPTION VISHAY CRCW06032M00FKEA OPTION
80 0 R53 RES, 0603 102kΩ 1% 1/10W OPTION VISHAY CRCW0603102KFKEA OPTION
81 0 R54 RES, 0603 11.3kΩ 1% 1/10W OPTION VISHAY CRCW060311K3FKEA OPTION
82 4 TP1, TP2, TP3, TP7 TURRET MILL-MAX 2308-2-00-80-00-00-07-0