ANALOG DEVICES DC2897A Evaluation Board User Manual
- June 5, 2024
- Analog Devices
Table of Contents
ANALOG DEVICES DC2897A Evaluation Board
DESCRIPTION
Demonstration circuit 2897A is a low IQ, triple output, synchronous step-down supply featuring the LTC®7819. The circuit is optimized for high efficiency. It provides outputs of 3.3V at 12A, 8.5V at 10A and 5.0V at 12A over an input voltage range of 10V to 36V with a switching frequency of 380kHz. Each rail uses a 3mΩ sense resistor to sense the current and provides optional footprints for DCR sensing. Typical applications include automotive, transportation, industrial, military and avionics systems. Features of the DC2897A include pin selectable light load operating modes of forced continuous mode, pulse-skipping and Burst Mode® operation. Optional spread spectrum modulation to reduce EMI, a PLLIN pin to synchronize to an external clock, optional DCR sensing footprints, an EXTVCC pin to reduce losses in the controller and optional footprints to parallel two or three channels. The LTC7819 data sheet provides a complete description of the part, operational details, and application information. DC2897A must be read in conjunction with the data sheet. Design files for this circuit board are available.
PERFORMANCE SUMMARY
PARAMETER| CONDITIONS| MIN| TYP| MAX| UNITS|
---|---|---|---|---|---|---
Input Voltage Range| | 10| 36| V|
Output Voltage #1, VOUT1| VIN = 10V to 36V, IOUT1 = 0A – 12A| 3.3| V|
Output Voltage #2, VOUT2| VIN = 10V to 36V, IOUT2 = 0A – 10A| 8.5| V|
Output Voltage #3, VOUT3| VIN = 10V to 36V, IOUT3 = 0A – 12A| 5.0| V|
Maximum Output Current, IOUT1| VIN = 10V to 36V, VOUT1 = 3.3V| 12| A|
Maximum Output Current, IOUT2| VIN = 10V to 36V, VOUT2 = 8.5V| 10| A|
Maximum Output Current, IOUT3| VIN = 10V to 36V, VOUT3 = 5.0V| 12| A|
Switching Frequency| | 380| kHz|
Efficiency (fSW = 380kHz)| VIN = 12V, VOUT1 = 3.3V, IOUT1 = 12A VIN = 12V,
VOUT2 = 8.5V, IOUT2 = 10A| 94.9
97.9
| %
%
|
| 96.4| %|
VIN = 12V, VOUT3 = 5.0V, IOUT3 = 12A|
QUICK START PROCEDURE
Demonstration circuit 2897A is easy to set up for evaluating the LTC7819. Please refer to Figure 1 for the proper measurement equipment setup and follow the procedure below.
-
Connect the input power supply to VIN (10V – 36V) and GND (input return).
-
Preset the load for each output to 0A and the input supply to 0V.
-
Place jumpers in the following positions:
JP4: RUN1 ON
JP2: RUN2 ON
JP1: RUN3 ON
JP3: MODE FCC
JP5: SPREAD SPECTRUM NO -
Set the input voltage to within the specified range and check VOUT1, VOUT2 and VOUT3.
-
Once the proper output voltages have been confirmed, observe the output voltage ripple, efficiency, and other parameters.
LIGHT LOAD OPERATION, SYNCHRONIZATION TO AN EXTERNAL CLOCK AND SPREAD SPECTRUM
To synchronize the LTC7819 to an external clock, place the SPREAD SPECTRUM jumper (JP5) in the EXT CLK position and apply an external clock between the PLLIN turret and GND. The phase-lockable frequency range is 100kHz to 3MHz. The low clock level should be 0.5V or lower and the high clock level should be 2.2V or higher. For spread spectrum, place the jumper in the YES posi-tion. With spread spectrum enabled, the frequency will be modulated between 100% and 120% of the programmed frequency (380kHz to 456kHz). This will help reduce the peak emission levels. To allow the converter to free run at is programmed frequency (380kHz), place the jumper in the NO position which is the default setting. Demonstration circuit 2897A can be programmed to operate in either forced continuous conduction mode (FCC), pulse-skipping mode (PS) or Burst Mode opera-tion (BURST) at no load or light load with JP3. Forced continuous mode (default setting) provides the clean-est output voltage ripple. Pulse- skipping mode provides higher efficiency at light load, but the output voltage ripple is less regular. Burst Mode operation provides the highest light load efficiency, but the output voltage ripple is the least regular and highest of the three modes.
QUICK START PROCEDURE
OPTIONAL DCR SENSING
Demonstration circuit 2897A has optional footprints for DCR sensing. The benefit of DCR sensing is a lower parts count and high efficiency but at the expense of a less accurate current sensing and current limit. To imple-ment DCR sensing refer to Table 1 and the Applications Information section of the data sheet. Be sure to stuff a 0mΩ copper shunt or a short, thick piece of copper at RS1, RS2 and/or RS3.
EXTVCC BIAS OPTION
The EXTVCC pin of the LTC7819 on the standard demo board is connected to the
5V output (VOUT3) to reduce the losses in the controller and improve
efficiency. If nec-
essary, the EXTVCC pin can be tied to an external supply by following these
steps:
- Remove the 0Ω jumper at R20.
- Connect a DC voltage from the EXTVCC turret to a GND turret. The DC voltage should be between 5V and 30V.
PARALLELING CHANNELS
For higher power, two or more channels of demonstra-tion circuit 2897A can be
paralleled. Given that the chan-nels operate 120 degrees out of phase with
each other, paralleling channels provides the benefit of ripple cur-rent
cancelation in the output and input capacitors. This in turn provides lower
output voltage and input voltage ripple. Another benefit of interleaved
channels is a faster load step response. When paralleling phases channel 1 is
always the master and channels 2 and 3 are slaves. In addition, each phase
should have the same inductor, sense resistor–if used and MOSFETs. Detailed
instruc-tions are below:
Table 1. Optional Inductor DCR Sensing
CONFIGURATION
| CHANNEL 1| RS1| R30| R29| C14| R45|
R47| R61
---|---|---|---|---|---|---|---|---
CHANNEL 2| RS2| R52| R54| C56| R50|
R49| R46
CHANNEL 3| RS3| R40| R39| C15| R51|
R53| R62
RSENSE (DEFAULT)| 3mΩ| 0Ω| 0Ω| 1nF| Open| Open| Open
DCR SENSING| 0mΩ Cu| Open| Open| Refer to Data Sheet| 0Ω
PARTS LIST
ITEM| QTY| REFERENCE| PART DESCRIPTION|
MANUFACTURER/PART NUMBER
---|---|---|---|---
1| 5| C1, C14, C15, C43, C56| CAP., 1000pF, C0G, 50V, 10%, 0603| AVX,
06035A102KAT2A
---|---|---|---|---
2| 1| C11| CAP., 4.7μF, X5R, 10V, 10%, 0805| KEMET, C0805C475K8PACTU MURATA,
GRM21BR61A475KA73L SAMSUNG, CL21A475KPFNNNF TDK, C2012X5R1A475K125AA
3| 8| C2, C4, C20, C21, C47, C52, C61, C74| CAP., 0.1μF, X7R, 50V, 10%, 0603|
AVX, 06035C104KAT2A
KEMET, C0603C104K5RAC7867; C0603C104K5RACTU TDK, C1608X7R1H104K080AA
4| 1| C41| CAP., 2200pF, X7R, 50V, 10%, 0603| AVX, 06035C222KAT2A
MURATA, GRM188R71H222KA01D SAMSUNG, CL10B222KB8NFNC
5| 2| C42, C44| CAP., 47pF, X7R, 50V, 10%, 0603| AVX, 06035C470KAT2A KEMET,
C0603C470K5RACTU
6| 1| C53| CAP., 0.01μF, C0G, 50V, 5%, 0603| MURATA, GRM1885C1H103JA01D TDK,
C1608C0G1H103J080AA
7| 1| C54| CAP., 220pF, X7R, 50V, 10%, 0603| AVX, 06035C221KAT2A KEMET,
C0603C221K5RACTU
NIC, NMC0603X7R221K50TRPF
8| 2| C69, C70| CAP., 1μF, X7R, 10V, 10%, 0603| AVX, 0603ZC105KAT2A KEMET, C0603C105K8RACTU
MURATA, GRM188R71A105KA61D TDK, C1608X7R1A105K080AC
9| 1| CIN1| CAP., 220μF, ALUM ELECT, 50V, 20%, 10mm × 10.2mm, RADIAL, SMD, AEC-Q200| PANASONIC, EEEFK1H221GP
CORNELL DUBILIER, AFK227M50G24T-F
10| 8| CIN3, CIN4, CIN5, CIN6, CIN7, CIN8, CIN9, CIN10| CAP., 4.7μF, X7R, 50V, 10%, 1210| AVX, 12105C475KAT2A KEMET, C1210C475K5RACTU
MURATA, GRM32ER71H475KA88L YAGEO, CC1210KKX7R9BB475
11| 6| COUT1, COUT2, COUT4, COUT5, COUT7, COUT8| CAP., 47μF, X7R, 10V, 10%, 1210| AVX, 1210ZC476KAT2A
MURATA, GRM32ER71A476KE15L
TAIYO YUDEN, LMK325B7476KM-PR; LMK325B7476KM-TR
12| 2| COUT10, COUT11| CAP., 470μF, TANT, POSCAP, 6.3V, 20%, 7343, 10mΩ, TCF|
PANASONIC, 6TCF470MAH
13| 1| COUT12| CAP., 150μF, TANT. POSCAP, 10V, 20%, 7343, D3L| PANASONIC,
10TPF150ML
14| 3| D1, D2, D6| DIODE, SCHOTTKY, 100V, 1A, POWERDI-123, AEC-Q101| DIODES
INC., DFLS1100Q-7
15| 2| L1, L3| IND., 2.2μH, PWR., 20%,
11.8mm × 10.5mm SMD, AEC-Q200
| COILCRAFT, XAL1010-222MEB; XAL1010-222MED
16| 1| L2| IND., 3.3μH, PWR., 20%, 25A, 4.10mΩ, 11.8mm × 10.5mm, XAL1010,
AEC-Q200| COILCRAFT, XAL1010-332MEB; XAL1010-332MED
17| 3| Q1, Q3, Q5| XSTR., MOSFET, N-CH, 40V, 59A, TDSON-8 FL| INFINEON,
BSC059N04LS6; BSC059N04LS6ATMA1
18| 3| Q2, Q4, Q6| XSTR., MOSFET, N-CH, 40V, 100A, TDSON-8 FL| INFINEON,
BSC022N04LS6; BSC022N04LS6ATMA1
19| 16| R1, R3, R4, R5, R9, R25, R27, R29, R30, R39, R40, R44, R52, R54, R83,
R84| RES., 0Ω, 1/10W, 0603, AEC-Q200| VISHAY, CRCW06030000Z0EA;
CRCW06030000Z0EB NIC, NRC06ZOTRF
ITEM| QTY| REFERENCE| PART DESCRIPTION|
MANUFACTURER/PART NUMBER
---|---|---|---|---
20| 1| R20| RES., 0Ω, 1/4W, 1206, AEC-Q200| VISHAY, CRCW12060000Z0EA
PANASONIC, ERJ8GEY0R00V NIC, NRC12ZOTRF
21| 3| R26, R38, R55| RES., 1M, 1%, 1/10W, 0603, AEC-Q200| NIC, NRC06F1004TRF
PANASONIC, ERJ3EKF1004V VISHAY, CRCW06031M00FKEA
22| 1| R31| RES., 10k, 1%, 1/10W, 0603, AEC-Q200| PANASONIC, ERJ3EKF1002V
VISHAY, CRCW060310K0FKEA; CRCW060310K0FKEB KOA SPEER, RK73H1JTTD1002F
23| 2| R33, R35| RES., 20k, 1%, 1/10W, 0603| NIC, NRC06F2002TRF VISHAY,
CRCW060320K0FKEA PANASONIC, ERJ3EKF2002V YAGEO, RC0603FR-0720KL
24| 1| R43| RES., 105k, 1%, 1/10W, 0603, AEC-Q200| VISHAY, CRCW0603105KFKEA
NIC, NRC06F1053TRF
25| 1| R57| RES., 133k, 1%, 1/10W, 0603| BOURNS, CR0603-FX-1333ELF YAGEO,
RC0603FR-07133KL
26| 1| R58| RES., 13.7k, 1%, 1/10W, 0603, AEC-Q200| VISHAY, CRCW060313K7FKEA
PANASONIC, ERJ3EKF1372V
27| 1| R6| RES., 1k, 5%, 1/10W, 0603, AEC-Q200| PANASONIC, ERJ3GEYJ102V
28| 1| R60| RES., 4.99k, 1%, 1/10W, 0603| PANASONIC, ERJ3EKF4991V YAGEO,
RC0603FR-074K99L
29| 4| R7, R34, R37, R63| RES., 100k, 1%, 1/10W, 0603, AEC-Q200| VISHAY,
CRCW0603100KFKEA NIC, NRC06F1003TRF PANASONIC, ERJ3EKF1003V
30| 3| R8, R36, R59| RES., 10Ω, 1%, 1/10W, 0603| VISHAY, CRCW060310R0FKEA NIC,
NRC06F10R0TRF PANASONIC, ERJ3EKF10R0V ROHM, MCR03EZPFX10R0 YAGEO, RC0603FR-
0710RL
31| 3| RS1, RS2, RS3| RES., 0.003, 0Ω, 1%, 2W, 2010 LONG- SIDE TERM, METAL,
SENSE, AEC-Q200| SUSUMU, KRL5025E-C-R003-F-T1
32| 1| U1| IC, SYN. STEP-DOWN CONVERTER, 40-PIN QFN| ANALOG DEVICES,
LTC7819RUJ#PBF; LTC7819RUJ#TRPBF
Additional Circuit Components
1| 0| C38, C48, C60, C62, C63, C64, C65, C66, C67, C68, C71, C72, C73| CAP.,
OPTION, 0603|
---|---|---|---|---
2| 0| CIN2| CAP., OPTION, ALUM. ELECT., SMD|
3| 0| COUT13, COUT14, COUT15| CAP., OPTION, 1210|
4| 0| COUT3, COUT6, COUT9| CAP., OPTION, 7343|
5| 0| Q7, Q10, Q11, Q12, Q13, Q14| XSTR., OPTION, MOSFET N-CH, PG-TDSON-8|
6| 0| R18, R19| RES., OPTION, 2010|
7| 0| R2, R10, R11, R12, R13, R14, R15, R21, R22, R23, R28, R32, R41, R42,
R45, R46, R47, R49, R50, R51, R53, R56, R61, R62| RES., OPTION, 0603|
Hardware: For Demo Board Only
1| 19| E1, E2, E3, E4, E5, E6, E7, E8, E9, E10, E11, E12, E13, E14, E15, E16,
E17, E18, E19| TEST POINT, TURRET, 0.094″ MTG. HOLE, PCB 0.062″ THK| MILL-MAX,
2501-2-00-80-00-00-07-0
---|---|---|---|---
2| 8| J1, J2, J3, J4, J5, J6, J7, J8| CONN., BANANA JACK, FEMALE, THT, NON-
INSULATED, SWAGE, 0.218″| KEYSTONE, 575-4
3| 3| JP1, JP2, JP4| CONN., HDR, MALE, 1×3, 2mm, VERT, ST, THT, NO SUBS.
ALLOWED| WURTH ELEKTRONIK, 62000311121
4| 2| JP3, JP5| CONN., HDR, MALE, 2×3, 2mm, VERT, ST, THT| WURTH ELEKTRONIK,
62000621121
5| 8| MP1, MP2, MP3, MP4, MP5, MP6, MP7, MP8| STANDOFF, NYLON, SNAP-ON, 0.625″
(5/8″), 15.9mm| KEYSTONE, 8834
6| 3| XJP1, XJP2, XJP4| CONN., SHUNT, FEMALE, 2-POS, 2mm| WURTH ELEKTRONIK,
60800213421
SCHEMATIC DIAGRAM
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