Analog Devices 2787A User manual

1
DEMO MANUAL DC2787A
Rev. 0
DESCRIPTION
LTC7821
High Efficiency, Polyphase Hybrid
Step Down Converter
Demonstration circuit 2787A is a high efficiency, 4 phase,
hybrid converter. It can deliver 12V/100A with the input
voltage from 40V to 60V. The demo board features the
LT C
®
7821, which uses an architecture that merges a soft-
switching switched-capacitor topology with a traditional
step-down converter to provide superior efficiency com-
pared to the traditional switching architectures. It offers
a high efficiency/high density and cost effective solution
for nonisolated intermediate bus applications in power
distribution, datacom and telecom as well as emerging
48V automotive systems.
External MOSFETs switch at a 400kHz fixed frequency for
this demo board and can be programmed from 200kHz to
1.5MHz. The LTC7821’s powerful 1Ω N-channel MOSFET
gate drivers maximize efficiency and can drive multiple
MOSFETs in parallel for higher power applications. Due to
its current mode control architecture, multiple LTC7821
devices can be operated in a parallel, multiphase con-
figuration with excellent current sharing and low output All registered trademarks and trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
voltage ripple to enable much higher power applications.
Other benefits include low EMI emissions due to a soft-
switched front end and reduced MOSFET stress.
The LTC7821 design eliminates the inrush current typically
associated with switched capacitor circuits by prebalancing
the capacitors on start-up. The LTC7821 also monitors sys-
tem voltage, current and temperature for faults, and uses a
sense resistor for overcurrent protection. It stops switch-
ing and pulls the FAULT pin low when a fault condition
occurs. An onboard timer can be set for appropriate restart/
retry times. Additional features include ±1% output voltage
accuracy over temperature, a clock output for multiphase
operation, a power good output signal, short-circuit protec-
tion, monotonic output voltage start-up, optional external
reference, undervoltage lockout and internal charge bal-
ance circuitry. The LTC7821 data sheet must be used in
conjunction with this demo board manual.
Design files for this circuit board are available.
Specifications are at TA= 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage Range 40 60 V
Output Voltage, VOUT VIN = 40-60V, IOUT = 0A to 100A 12 V
Maximum Output Current, IOUT VIN = 40-60V, VOUT = 12V 100 A
Typical Efficiency VIN = 48V, VOUT = 12V, IOUT = 100A 97.6 %
Peak Efficiency VIN = 48V, VOUT = 12V 98 %
Switching Frequency 400 kHz

2
DEMO MANUAL DC2787A
Rev. 0
BOARD PHOTO
Figure1. 4x LTC7821; 100A DC2787A Demo Circuit

3
DEMO MANUAL DC2787A
Rev. 0
QUICK START PROCEDURE
Demonstration circuit 2787A is easy to set up to evaluate
the performance of the LTC7821. Refer to Figure2 for
the proper measurement equipment setup and follow the
procedure below.
1. With power off, connect the input power supply to VIN
(40V-60V) and GND (input return).
2. Connect the output loads between VOUT and GND
(Initial load: no load). Refer to Figure2.
3. Connect the DVMs to the input and output.
4. Check the default jumper/switch position:SW1 (RUN):
OFF; JP2 (BIAS): ON.
5. Turn on the input power supply and adjust voltage to 48V;
NOTE. Make sure that the input voltage does not exceed 60V.
6. Turn on the switches: SW1: ON.
7. Check for the proper output voltages from VO_SNS+
to VO_SNS−.
8. Once the proper output voltage is established, adjust
the loads within the operating range and measure the
efficiency, output ripple voltage and other parameters.
9. After completing all tests, adjust the load to 0A, power
off the input power supply.
Notes:
1. When measuring the output or input voltage ripple, do
not use the long ground lead on the oscilloscope probe.
See Figure3 for the proper scope probe technique. Short,
stiff leads need to be soldered to the (+) and (−) terminals
of an output capacitor. The probe’s ground ring needs to
touch the (−) lead and the probe tip needs to touch the
(+) lead.
2. When doing the load step test with the on-board
dynamic load circuit, please make sure the load step-up
pulse duty cycle does not exceed 2% and the pulse dura-
tion is less than 500µs so that the temperature of the
MOSFETs Q20, Q21 in the dynamic load circuit stay in the
safe region. Instead of using the on-board dynamic load
circuit, an electric load can also be used for the load step
test, which does not have the 2% max duty cycle limit for
the load step.

4
DEMO MANUAL DC2787A
Rev. 0
QUICK START PROCEDURE
V
-
+
+-
Load (0~100A)
1mΩ
V
-
V
+
VIN
40V-60V
A
+
-
+
-
Figure2. Proper Measurement Equipment Setup
Figure3. Measuring Output Voltage Ripple

5
DEMO MANUAL DC2787A
Rev. 0
QUICK START PROCEDURE
Figure4. Efficiency vs Load Current at VOUT = 12V, fSW = 400kHz
Figure5. Current Sharing vs Load Current at VIN = 48V, VOUT = 12V, fSW = 400kHz
DC2787A F04
90
92
94
96
98
100
0 20 40 60 80 100
EFFICIENCY (%)
40VIN
48VIN
60VIN
OUTPUT LOAD CURRENT (A)
DC2787A F05
0
5
10
15
20
25
30
0 20 40 60 80 100
LOAD CURRENT PER PHASE (A)
TOTAL LOAD CURRENT (A)
PHASE #1
PHASE #2
PHASE #3
PHASE #4
Efficiency vs Load Current
Current Sharing vs Load Current

6
DEMO MANUAL DC2787A
Rev. 0
QUICK START PROCEDURE
50μ/DIV
VOUT(20MHz BW)
100mV/DIV
50A-75A-50A LOAD
20A/DIV
2787A F06
Figure6. Load Step at VIN = 48V, VOUT = 12V
Figure7. Thermal performance VIN = 48V, VOUT = 12V, IOUT = 100A TA = 23˚C, No Airflow
Figure8. Thermal performance VIN = 48V, VOUT = 12V, IOUT = 100A A = 23˚C, 200LFM Airflow

7
DEMO MANUAL DC2787A
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 8 C1, C6, C68-C70, C74,
C153, C154
CAP.,33uF,ALUM. ELECT.,80V,20%,10x10.2mm SMD,
RADIAL,AEC-Q200
PANASONIC, EEHZA1K330P
2 26 C2, C3, C7, C47, C49,
C56, C58, C59, C71-C73,
C85-C88, C103-C105,
C109, C119, C203,
C206-C210
CAP.,2.2uF,X7R,100V,10%,1210 AVX, 12101C225KAT2A
3 16 C4, C5, C12, C13, C15,
C17, C37, C91, C95,
C107, C166, C169, C174,
C175, C287, C288
CAP.,0.1uF,X7S,100V,10%,0603 TAIYO YUDEN, HMK107C7104KA-T
4 8 C8, C14, C40, C106,
C108, C165, C167, C170
CAP.,0.22uF,X7R,25V,10%,0603 YAGEO, CC0603KRX7R8BB224
5 4 C9, C102, C164, C173 CAP.,0.47uF,X7R,25V,10%,0603 AVX, 06033C474KAT2A
6 113 C10, C11, C18-C25,
C28-C36, C38, C41, C43,
C60-C67, C75-C83, C90,
C92-C94, C98-C101,
C111-C118, C121-C150,
C176-C202, C216
CAP.,10uF,X7S,100V,10%,1210 MURATA, GRM32EC72A106KE05L
7 4 C26, C120, C157, C158 CAP.,2.2uF,X5R,25V,10%,0603 MURATA, GRM188R61E225KA12D
8 5 C27, C50, C96, C159,
C162
CAP.,1uF,X7R,25V,10%,0603,AEC-Q200 MURATA, GCM188R71E105KA64D
9 1 C39 CAP.,4.7nF,X7R,25V,10%,0603 AVX, 06033C472KAT2A
10 8 C42, C44, C57, C84, C89,
C97, C152, C155
CAP.,150uF,ALUM./OS-CON,16V,20%,8x6.9mm
SMD, RADIAL
PANASONIC, 16SVPC150M
11 4 C45, C110, C156, C215 CAP.,27pF,C0G,250V,5%,0603 MURATA, GQM1875C2E270JB12D
12 2 C52, C53 CAP.,22uF,X5R,25V,10%,1210 MURATA, GRM32ER61E226KE15K
13 1 C54 CAP.,0.047uF,X7R,25V,10%,0603 AVX, 06033C473KAT2A
14 1 C55 CAP.,220pF,C0G,50V,5%,0603 AVX, 06035A221JAT2A
15 4 C255, C257, C259, C261 CAP.,4.7uF,X5R,16V,10%,0603 MURATA, GRM188R61C475KE11D
16 4 C256, C258, C260, C262 CAP.,4.7uF,X5R,50V,10%,0805 MURATA, GRM21BR61H475KE51L
17 12 D1-D6, D11-D16 DIODE,SCHOTTKY,40V,250mW,SOD-323 CENTRAL SEMI., CMDSH-4E TR Lead Free
18 4 L1-L4 IND.,2uH,PWR. SHIELDED,20%,40A,1.34mOhms,19
.69x19.55x10.67mm, SMD,AEC-Q200
COILCRAFT, SER2011-202MLB
19 1 L5 IND.,68uH,PWR, SHIELDED,20%,0.74A,0.42
OHM,2424, LPS6225
COILCRAFT, LPS6225-683MRB
20 4 Q1, Q2, Q11, Q13 XSTR.,MOSFET, N-CH,80V,40A,TSDSON-8 FL INFINEON, BSZ070N08LS5
21 8 Q3-Q6, Q9, Q10, Q15,
Q16
XSTR.,MOSFET, N-CH,40V,98A,TDSON-8 INFINEON, BSC032N04LS
22 4 Q7, Q8, Q12, Q14 XSTR.,MOSFET, N-CH,40V,100A,TDSON-8 FL INFINEON, BSC014N04LSI
23 2 Q20, Q21 XSTR.,MOSFET, N-CH,40V,TO-252 (DPAK) VISHAY, SUD50N04-8M8P-4GE3
24 8 R1, R7, R19, R38, R42,
R58, R59, R61
RES.,1k OHM,1%,1/10W,0603 VISHAY, CRCW06031K00FKEA

8
DEMO MANUAL DC2787A
Rev. 0
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
25 4 R2, R36, R53, R56 RES.,AEC-Q200,1 OHM,5%,1/10W,0603 VISHAY, CRCW06031R00JNEA
26 43 R5, R10-R12, R14,
R20, R24, R32, R33,
R35, R40, R41, R45,
R47, R50, R51, R76,
R226-R231, R240, R241,
R246, R252, R254-R256,
R258, R264, R266-R268,
R270, R271, R273-R276,
R278, R279
RES.,0 OHM,1/10W,0603 VISHAY, CRCW06030000Z0EA
27 1 R6 RES.,AEC-Q200,1M OHM,1%,1/8W,0805 PANASONIC, ERJ6ENF1004V
28 1 R8 RES.,34k OHMS,1%,1/10W,0603 NIC, NRC06F3402T
29 9 R9, R13, R22, R28, R49,
R60, R62, R272, R277
RES.,AEC-Q200,10k OHMS,1%,1/10W,0603 VISHAY, CRCW060310K0FKEA
30 4 R15, R37, R52, R57 RES.,100k OHMS,1%,1/10W,0603 VISHAY, CRCW0603100KFKEA
31 4 R16, R48, R64, R68 RES.,53.6k OHMS,1%,1/10W,0603,AEC-Q200 VISHAY, CRCW060353K6FKEA
32 4 R17, R43, R70, R71 RES.,AEC-Q200,6.81k OHMS,1%,1/8W,0805 VISHAY, CRCW08056K81FKEA
33 1 R18 RES.,3.74k OHMS,1%,1/10W,0603 PANASONIC, ERJ3EKF3741V
34 4 R23, R75, R244, R259 RES.,AEC-Q200,60.4k OHMS,1%,1/10W,0603 VISHAY, CRCW060360K4FKEA
35 4 R25, R66, R245, R248 RES.,AEC-Q200,4.32k OHMS,1%,1/10W,0603 VISHAY, CRCW06034K32FKEA
36 1 R26 RES.,182k OHMS,1%,1/10W,0603,AEC-Q200 PANASONIC, ERJ3EKF1823V
37 1 R27 RES.,20k OHMS,5%,1/10W,0603,AEC-Q200 NIC, NRC06J203TRF
38 1 R29 RES.,80.6k OHMS,1%,1/10W,0603 VISHAY, CRCW060380K6FKEA
39 2 R30, R247 RES.,0.2 OHM,1%,1/2W,2010,SENSE, AEC-Q200 VISHAY, WSL2010R2000FEA
40 1 SW1 SWITCH,SLIDE,DPDT,0.3A,6VDC,PTH C&K, JS202011CQN
41 4 U1-U4 IC, Hybrid Step-Down Synchronous Controller QFN-32 ANALOG DEVICES, LTC7821EUH#PBF
42 1 U7 IC, SYNCHRONOUS STEP-DOWN CONVERTER ANALOG DEVICES, LTC3630AEMSE#PBF
Additional Demo Board Circuit Components
1 0 C16, C46, C48, C51,
C160, C171, C172,
C290-C295
CAP., OPTION, 0603
2 0 Q1A, Q1A1, Q11A,
Q11A1, Q22, Q22A,
Q22A1-Q22A3, Q25, Q26,
Q29, Q30, Q33, Q34, Q37
XSTR., OPTION, MOSFET N-CH, PPAK SO-8
3 0 Q23, Q24, Q27, Q28,
Q31, Q32, Q35, Q36
XSTR., OPTION, MOSFET N-CH, PG-TDSON-8
4 0 R3, R31, R34, R44, R46,
R65, R74, R234, R235,
R250, R251, R253,
R262, R263, R265
RES., OPTION, 0603
5 0 RN1-RN4 THERMISTOR, OPTION, 0603
PARTS LIST

9
DEMO MANUAL DC2787A
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Hardware
1 14 E1-E6, E8-E15 TEST POINT,TURRET,0.094",MTG. HOLE MILL-MAX, 2501-2-00-80-00-00-07-0
2 4 J1-J4 STUD, FASTENER, #10-32 PENNENGINEERING, KFH-032-10ET
3 2 J5, J6 CONN.,RF, BNC,RCPT JACK,5-PIN,STR, THT,50 Ohms AMPHENOL RF, 112404
4 4 J1-J4 RING, LUG, CRIMP,#10,NON-
INSULATED,SOLDERLESS TERMINALS
KEYSTONE, 8205
5 8 J1-J4 NUT,HEX,#10-32,BRASS PENCOM, NU1132
6 1 JP2 CONN.,HDR,MALE,1x3,2mm,STR, THT,NO SUBS.
ALLOWED
Wurth Elektronik, 62000311121
7 4 J1-J4 WASHER,#10,LOCK,EXT,TIN FINISH PENCOM, WA4526
8 6 MH1-MH6 STANDOFF,NYLON,SNAP-ON,0.625" KEYSTONE, 8834
9 1 XJP2 CONN.,SHUNT,FEMALE,2 POS,2mm Wurth Elektronik, 60800213421

10
DEMO MANUAL DC2787A
Rev. 0
SCHEMATIC DIAGRAM
5 5
4 4
3 3
2 2
1 1
D D C C B B A A
12V / 100A
NOTES: UNLESS OTHERWISE SPECIFIED,
1. CAPACITORS AND RESISTORS ARE 0603.
SER2011-202MLD
ON
RUN
OFF
40V~60V
APPROVEDECO
3 PROD 02/20/19
DATEREV
REVISION HISTORY
` `
DESCRIPTION
INTVCC1
VOUT
EXTVCC
VOUT
INTVCC1
VOUT
VIN
INTVCC1
VIN
INTVCC1
INTVCC1
VIN
VIN
VIN
VIN
VOUTA
RUN
TRACK/SS
ITH
VFB
CLKOUT1
FAULT
PGOOD
DATE:
IC NO.
SHEET OF
TITLE: DEMO CIRCUIT SCHEMATIC,
APPROVALS
PCBDES. APPENG. Phone:1‐408‐432‐1900
Milpitas,CA95035 1630McCarthyBlvd.
ForADICustomerUseOnly
CUSTOMER NOTICE
ANALOGDEVICESINC.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 INC.APPLICATIONSENGINEERINGFORASSISTANCE.
THISCIRCUITISPROPRIETARYTOANALOGDEVICESINC.AND SUPPLIEDFORUSEWITHANALOGDEVICESINC.PARTS.
SCALE=NONE
SIZE:
SKU NO. SCHEMATIC NO. AND REVISION:
PCABOM: PCAASS'Y:
www.analog.com
41
` \
` `
LTC7821
DC2787A
700-DC2787A_REV03
705-DC2787A_REV03
N/A
Thursday, May 16, 2019
710-DC2787A_REV03
HIGH EFFICIENCY, POLYPHASE HYBRID STEP-DOWN
CONVERTER
DATE:
IC NO.
SHEET OF
TITLE: DEMO CIRCUIT SCHEMATIC,
APPROVALS
PCBDES. APPENG. Phone:1‐408‐432‐1900
Milpitas,CA95035 1630McCarthyBlvd.
ForADICustomerUseOnly
CUSTOMER NOTICE
ANALOGDEVICESINC.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 INC.APPLICATIONSENGINEERINGFORASSISTANCE.
THISCIRCUITISPROPRIETARYTOANALOGDEVICESINC.AND SUPPLIEDFORUSEWITHANALOGDEVICESINC.PARTS.
SCALE=NONE
SIZE:
SKU NO. SCHEMATIC NO. AND REVISION:
PCABOM: PCAASS'Y:
www.analog.com
41
` \
` `
LTC7821
DC2787A
700-DC2787A_REV03
705-DC2787A_REV03
N/A
Thursday, May 16, 2019
710-DC2787A_REV03
HIGH EFFICIENCY, POLYPHASE HYBRID STEP-DOWN
CONVERTER
DATE:
IC NO.
SHEET OF
TITLE: DEMO CIRCUIT SCHEMATIC,
APPROVALS
PCBDES. APPENG. Phone:1‐408‐432‐1900
Milpitas,CA95035 1630McCarthyBlvd.
ForADICustomerUseOnly
CUSTOMER NOTICE
ANALOGDEVICESINC.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 INC.APPLICATIONSENGINEERINGFORASSISTANCE.
THISCIRCUITISPROPRIETARYTOANALOGDEVICESINC.AND SUPPLIEDFORUSEWITHANALOGDEVICESINC.PARTS.
SCALE=NONE
SIZE:
SKU NO. SCHEMATIC NO. AND REVISION:
PCABOM: PCAASS'Y:
www.analog.com
41
` \
` `
LTC7821
DC2787A
700-DC2787A_REV03
705-DC2787A_REV03
N/A
Thursday, May 16, 2019
710-DC2787A_REV03
HIGH EFFICIENCY, POLYPHASE HYBRID STEP-DOWN
CONVERTER
C15 0.1uF
C59 2.2uF 100V 1210
Q1A OPT
5
6
7
4
2
3
8
1
U1
LTC7821EUH
MODE/PLLIN
1
CLKOUT
2
RUN
3
FAULTB
4
PGOOD
5
TIMER
6
TRACK/SS
7
EXT_REF
8
ISENSE+
15
EXTVCC
16
ISENSE-
14
PGND
17
BG2
18
INTVCC
19
SW3
20
TG2
21
BG1
24
HYS_PRGM
9
ITH
10
FREQ
11
TEMP
12
VFB
13
BOOST3
22
BOOST2
23
MID
25
MIDSENSE
26
VINSENSE
27
VIN
28
SW1
29
TG1
30
BOOST1
31
NC
32
SGND
33
J3
VOUT
C23
+
C89 150uF 16V
12
C36 10uF
C3 2.2uF 100V 1210
D3
CMDSH-4E
21
+
C74
12
R6
1M
0805
C67
1210
R240
0
R10 0
Q1
BSZ070N08LS5
4
5
6
7
8
3
1
2
C31 10uF
1210
C63 C19
+
C153
12
R12
0
+
C68
12
R246
0
R15
100k
C73
Q24 OPT
4
5
6
7
8
3
1
2
E1
VIN
C45
27pF
+
C154
12
R5 0
E10
PLLIN
C24
1210
C26 2.2uF
R2
1
R250
OPT
L1 2uH
E4
EXTVCC
R31
OPT
+
C6 33uF
80V
12
E6
VO_SNS-
Q7
BSC014N04LSI
4
5
6
7
8
3
1
2
R9 10k
1%
C37 0.1uF
R25 4.32k 1%
C2 2.2uF 100V 1210
R20
0
J1
VIN
C48
OPT
C34 10uF
C105
2.2uF
1210
C8
0.22uF
SW1
1
2
34
5
6
C41 10uF
100V
1210
C72 R3
OPT
R7 1k
RN1
OPT
t°
+
C84
150uF
16V
12
C60
10uF
100V
C32
10uF
C20
D2
CMDSH-4E
2 1
J2
GND
R270
0
R226 0
C103
100V
R16
53.6k
1%
E2
GND
C255
4.7uF
C64
10uF
100V
C46
OPT
+
C97 150uF
16V
12
E13
FAULT
E14
RUN
C56
100V
C207
Q3
BSC032N04LS
4
5
6
7
8
3
1
2
C16 OPT
R33
0
C61
C39
4.7nF
+
C70
12
C25
C35 10uF
C256 4.7uF
0805
C208
R32
0
E5
VO_SNS+
C5
0.1uF
C71
2.2uF
1210
R1 1k
Q22 OPT
4
5
6
7
8
3
1
2
D1
CMDSH-4E
2 1
Q23 OPT
4
5
6
7
8
3
1
2
+
C1 33uF
80V
12
E11
PGOOD
R17
6.81k
0805
R23 60.4k 1%
C65
+
C44 150uF 16V
12
E3
GND
R8
34k
1%
+
C152
150uF
16V
12
R271
0
Q22A OPT
5
6
7
4
2
3
8
1
C29 10uF 100V
R227
0
J4
GND
C43 10uF
100V
1210
C18 10uF 100V 1210
C58 2.2uF 100V 1210
R13 10k
1%
C62
1210
C27 1uF
C22 10uF
100V
+
C155 150uF
16V
12
Q5
BSC032N04LS
4
5
6
7
8
3
1
2
C33 10uF
100V
1210
Q25 OPT
4
5
6
7
8
3
1
2
C40 0.22uF
C10 10uF
100V
1210
+
C42 150uF 16V
12
C9 0.47uF
C66
R18
3.74k
+
C69
12
C81 10uF
100V
1210
+
C57 150uF 16V
12
C30 10uF
C4
0.1uF
C21
FAULT