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DC2995A High Frequency, Step Down Supply, GaN FETs

Analog Devices DC2995A High Frequency, Step Down Supply, GaN FETs User manual

  • Hello! I've reviewed the user manual for the DC2995A LTC7891 Step-Down Supply. This manual provides details on a high-frequency step-down supply utilizing GaN FETs, highlighting its 36V-72V input range, 12V/20A output, and high efficiency. I'm ready to answer your questions about the device and its specifications.
  • What is the input voltage range for the DC2995A?
    What is the output voltage of the DC2995A?
    What is the switching frequency of the DC2995A?
    What is the efficiency of the converter at 20A load?
1
DEMO MANUAL DC2995A
Rev. A
DESCRIPTION
LTC7891
High Frequency Step-Down
Supply with GaN FETs
Demonstration circuit 2995A is a buck regulator featuring
the LT C
®
7891. The DC2995A operates from a 36V to 72V
input voltage range and generates a 12V, 20A output.
The LTC7891 has a precision voltage reference which can
generate an output voltage with 2% tolerance over the full
operating conditions. The 500kHz switching frequency
operation results in a small and efficient circuit. The con-
verter achieves over 96% efficiency with 20A load.
All registered trademarks and trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
The demonstration circuit can be easily modified to regu-
late output voltages from 0.8V to 60V.
The DC2995A provides a high performance cost-effective
solution for generating a 12V output. The LTC7891 data
sheet gives a complete description of this part, its opera-
tion and application information and must be read in con-
junction with this demo manual.
Design files for this circuit board are available.
Specifications are at TA = 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage IOUT = 0A to 20A 36 V
Maximum Input Voltage IOUT = 0A to 20A 72 V
Output Voltage VIN = 36V to 72V 12 ±2% V
Output Voltage Ripple VIN = 48V, IOUT = 20A 300 mVP-P
Nominal Switching Frequency 500 kHz
2
DEMO MANUAL DC2995A
Rev. A
QUICK START PROCEDURE
Demonstration circuit 2995A is easy to set up to evaluate
the performance of the LTC7891. For proper measure-
ment equipment setup refer to Figure1 and follow the
procedure below.
NOTE: When measuring the input or output voltage ripple,
care must be taken to minimize the length of oscilloscope
probe ground lead. Measure the input or output voltage
ripple by connecting the probe tip directly across the VIN
or VOUT and GND terminals as shown in Figure2.
1. With power off, connect the input power supply to VIN
and GND.
2. Keep the load set to 0A or disconnected.
3. Turn the input power source on and slowly increase the
input voltage.
NOTE: Make sure that the input voltage VIN does not
exceed 72V.
4. Set the input voltage to 48V and check for the proper
output voltage of 12V. If there is no output, temporarily
disconnect the load to make sure that the load is not
set too high.
5. Once the proper output voltage is established, adjust
the load, and observe the output voltage regulation,
ripple voltage, efficiency, and other parameters.
Figure1. Proper Measurement Equipment Setup
Figure2. Measuring Input or Output Ripple
+ –
V
OUT
GND
COUT
3
DEMO MANUAL DC2995A
Rev. A
QUICK START PROCEDURE
Changing the Output Voltage
To change the output voltage from the programmed
12V, change the voltage setting resistors connected to
LTC7891 FB pin (see Schematic Diagram section). Also,
change all the power components required to meet the
desired output voltage.
Converter Efficiency and Output Current
Typical performance of DC2995A is shown in Figure3.
The efficiency is high even at light loads thanks to Burst
Mode
®
operation.
Figure3. The 12V Output Efficiency is 96.1% with 20A Load
Figure4. The LTC7891 Has Good Load Step Response
with Small Output Capacitors
Figure5. The DC2995A Ramps the Output Slowly at
Start-Up without Output Voltage Overshoot
Burst Mode OPERATION
V
IN
= 36V
V
IN
= 48V
V
IN
= 72V
OUTPUT CURRENT (A)
0
2
4
6
8
10
12
14
16
18
20
80
82
84
86
88
90
92
94
96
98
EFFICIENCY (%)
DC2995A F03
Output Load Step Response
The load step response of DC2995A is dependent on the
amount and type of output caps used. For higher load
steps more output capacitance can be added to keep the
voltage transients at the desired level. The 10A load step
transients with 48V input are shown in Figure4. Other
types of low ESR and high value capacitors can be used if
space is available to reduce load transients to desired level.
V
IN
= 48V, V
OUT
=12V, I
OUT
= 5A
BURST MODE, 10A LOAD STEP
100µs/DIV
V
OUT
200mV/DIV
I
OUT
10A/DIV
DC2995A F04
V
IN
= 48V, V
OUT
= 12V, I
OUT
= 20A
CCM, RUN-START-UP
2ms/DIV
V
OUT
5V/DIV
RUN
1V/DIV
I
IN
5A/DIV
DC2995A F05
Start-Up and Soft-Start Function
The DC2995A features a soft-start circuit that ramps
the output voltage up in monotonic fashion as shown in
Figure5. The soft-start circuit also prevents output voltage
overshoot when output voltage ramp reachesregulation.
When RUN pin is enabled, the output voltage will start
ramping up after 1ms delay that is required for INTVCC
pin to reach the internal UVLO level.
4
DEMO MANUAL DC2995A
Rev. A
QUICK START PROCEDURE
Figure6. The LTC7891 Has Only 54.2°C Temperature Rise with
48V Input, 12V Output and 20A Load. (TA = 25°C, No Cooling Fan)
Thermal Performance
The LTC7891 features excellent thermal performance due
to high efficiency of synchronous buck circuit. The tem-
perature rises of LTC7891 with 48V input and 20A load
is shown in Figure6.
The six-layer PCB layout features solid copper planes that
provide heat spreading across the whole board.
5
DEMO MANUAL DC2995A
Rev. A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 CAP., 4.7µF, X5R, 25V, 10%, 0603 MURATA, GRM188R61E475KE11D
2 3 C2, C3, C17 CAP., 0.1µF, X7R, 25V, 10%, 0603 AVX, 06033C104KAT2A
3 1 C7 CAP., 1000pF, X7R, 25V, 10%, 0603 AVX, 06033C102KAT2A
4 2 C10, C24 CAP., 100pF, C0G, 25V, 10%, 0603 AVX, 06033A101KAT2A
5 1 C14 CAP., 4700pF, C0G/NP0, 50V, 5%, 0603 AVX, 06035A472JAT2A
6 1 C15 CAP., 1µF, X5R, 50V, 10%, 0603, AEC-Q200 MURATA, GRT188R61H105KE13D
7 1 C23 CAP., 1µF, X7R, 25V, 10%, 0603, AEC-Q200 MURATA, GCM188R71E105KA64D
8 1 C25 CAP., 0.1µF, X7R, 100V, 10%, 0603 AVX, 06031C104KAT2A
9 2 CIN1, CIN2 CAP., 47µF, ALUM. POLY. HYB., 80V, 20%, 10mm × 10.2mm
SMD, RADIAL, AEC-Q200
PANASONIC, EEHZC1K470P
10 2 CIN3, CIN4 CAP., 22µF, X7S, 100V, 20%, 2220, STACKED TDK, CKG57NX7S2A226M500JH
11 2 CIN7, CIN12 CAP., 1µF, X7S, 100V, 10%, 0805, SOFT TERM. MURATA, GRJ21BC72A105KE11L
12 4 CIN8-CIN11 CAP., 10µF, X7S, 100V, 10%, 1210 MURATA, GRM32EC72A106KE05L
13 2 COUT5, COUT7 CAP., 150µF, TANT., 16V, 20%, 7343 PANASONIC, 16TQC150MYF
14 4 COUT8-COUT11 CAP., 22µF, X7R, 16V, 10%, 1210 MURATA, GRM32ER71C226KEA8L
15 1 L1 IND., 3.1µH, WE-HCF, PWR, 15%, 16A, 2.09mΩ, 2013 WURTH ELEKTRONIK, 7443630310
16 4 Q1, Q2, Q7, Q8 XSTR., MOSFET, N-CH, E-Mode, 100V, 90A, GaNPX-4,
BOTTOM-SIDE COOLED
GAN SYSTEMS INC., GS61008P-MR
17 9 R2, R4, R24, R25, R29,
R59, R78, R79, R81
RES., 0Ω, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06030000Z0EA
18 2 R5, R62 RES., 1M, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06031M00FKEA
19 4 R6, R8, R13, R15 RES., 2.2Ω, 5%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3GEYJ2R2V
20 1 R17 RES., 10Ω, 1%, 1/10W, 0603 VISHAY, CRCW060310R0FKEA
21 1 R18 RES., 604k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603604KFKEA
22 1 R19 RES., 43.2k, 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF4322V
23 1 R20 RES., 10k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW060310K0FKEA
24 1 R37 RES., 73.2k, 1%, 1/10W, 0603 NIC, NRC06F7322TRF
25 1 R49 RES., 1k, 1%, 1/10W, 0603 VISHAY, CRCW06031K00FKEA
26 1 R57 RES., 100k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603100KFKEA
27 1 R63 RES., 34.8k, 1%, 1/10W, 0603 VISHAY, CRCW060334K8FKEA
28 1 RS1 RES., 0.0015Ω, 1%, 3W, 2512, METAL, SENSE, AEC-Q200 VISHAY, WSLP25121L500FEA
29 1 U1 IC, STEP-DOWN CONTROLLER FOR GaN FETs, QFN-28 ANALOG DEVICES, LTC7891RUFDM#PBF
6
DEMO MANUAL DC2995A
Rev. A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Additional Demo Board Circuit Components
1 0 C16 CAP., OPTION, 0603
2 0 CIN13-CIN16 CAP., 10µF, X7S, 100V, 10%, 1210 MURATA, GRM32EC72A106KE05L
3 0 COUT6, COUT18 CAP., OPTION, 7343
4 0 D4 DIODE, SCHOTTKY, 100V, 12A, SO-8FL, AEC-101 ON SEMICONDUCTOR, NTS12100EMFST1G
5 0 D5 DIODE, SCHOTTKY BARRIER 100V 200mA SOD-323 ON SEMICONDUCTOR, NSR02100HT1G
6 0 R30, R31, R34, R38, R53,
R61, R70-R77, R80, R82
RES., OPTION, 0603
7 0 R69 RES., OPTION, 2512
8 1 SW1 SWITCH SLIDE DPDT 300MA 6V THROUGH HOLE C&K, JS202011CQN
9 4 J1, J2, J5, J6 EVAL BOARD STUD HARDWARE SET, #10-32 ANALOG DEVICES, 720-0010
10 0 L1 IND., OPTION, 3.6µH, PWR, SHIELDED, 20%, 30A, 1.82mΩ,
19.69mm × 19.56mm × 12.95mm, SER2013, AEC-Q200
COILCRAFT, SER2013-362MLB
7
DEMO MANUAL DC2995A
Rev. A
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
FCM
BURST MODE
PULSE SKIP
EXTERNAL VCC BLEEDER LOADS
73.2k for 500kHz
REV DATEECO APPROVEDDESCRIPTION
05/27/22
PROTO G P
REVISION HISTORY
4
* Note: L2 is optional footprint.
OPT
OPT
OPT
OPT
VOUT INTVCC
INTVCC
INTVCC
INTVCC
VIN
VIN
INTVCC
VOUT
VOUT
EXTVCC
EXTVCC
INTVCC
INTVCC
VINVIN
VOUT
INTVCC
INTVCC
INTVCC
INTVCC
INTVCC
VIN
DATE:
SHEET OF
TITLE: SCHEMATIC
APPROVALS
PCB DES.
APP ENG.
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.
1 1
A N
G P
LTC7891RUFDM
HIGH FREQUECY, STEP-DOWN SUPPLY with GaN FET
DC2995A
710-DC2995A_REV04
NONE
Friday, May 27, 2022
DATE:
SHEET OF
TITLE: SCHEMATIC
APPROVALS
PCB DES.
APP ENG.
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.
1 1
A N
G P
LTC7891RUFDM
HIGH FREQUECY, STEP-DOWN SUPPLY with GaN FET
DC2995A
710-DC2995A_REV04
NONE
Friday, May 27, 2022
DATE:
SHEET OF
TITLE: SCHEMATIC
APPROVALS
PCB DES.
APP ENG.
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.
1 1
A N
G P
LTC7891RUFDM
HIGH FREQUECY, STEP-DOWN SUPPLY with GaN FET
DC2995A
710-DC2995A_REV04
NONE
Friday, May 27, 2022
R53
OPT
R19
43.2k
R80
OPT
R74
OPT
C7
1nF
E11
TRK / SS
C25
0.1uF
100V
R17
10
C1
4.7uF
J5
VOUT
12V / 20A
C15
1uF
R8
2.2
+
COUT5
150uF
7343
16V
E3
VIN+
CIN14
JP3
PLLIN/SPREAD
DISABLE SS
ENABLE SS
EXTERNAL SYNC
1 2
3 4
5 6
R6
2.2
C14
4.7nF
CIN4
22uF
2220
100V
R25
0
COUT9
22uF
1210
16V
D4
3
2
1
5
6
C16
OPT
C17
0.1uF
Q2
GS61008P
5
3 1
2
4
E17
GND
Q7
GS61008P
5
3 1
2
4
R30
OPT
R20
10k
+
COUT6
OPT
7343
12
R82
OPT
CIN12
1uF
100V
0805
R59
0
SW1
ON
OFF
RUN
1
2
3
4
5
6
J6
GND
R73
OPT
R81
0
CIN7
1uF
100V
0805
R38
OPT
C24
100pF
E8
GND
C3 0.1uF
R62
1M
C23
1uF
TP2
R71
OPT
J1
VIN
36V - 72V
CIN16
+
COUT18
OPT
7343
12
R34
OPT
CIN10
10uF
1210
100V
R70
OPT
E4
GND
R49 1k
COUT10
22uF
1210
16V
R72
OPT
COUT11
22uF
1210
16V
+
CIN2
47uF
80V
12
R79
0
R69
OPT
2512
Q8
GS61008P
5
3 1
2
4
E12
EXTVCC
R76
OPT
COUT8
22uF
1210
16V
E13
GND
CIN3
22uF
2220
100V
R61
OPT
CIN8
10uF
1210
100V
R15
2.2
E10
SYNC
JP1
MODE
1 2
3 4
5 6
D5
2 1
R29
0
L1
3.1uH, WE-HCF
1 2
Q1
GS61008P
5
3 1
2
4
CIN15
R77
OPT
J2
GND
E6
VOUT
R31
OPT
R24
0
C10
100pF
R37
73.2k 1%
CIN13
C2
0.1uF
R75
OPT
E2
PGOOD
R78
0
R63
34.8k
R4
0
R57
100k
TP3
U1
LTC7891RUFDM
DTCB
24
PLLIN/SPREAD
1
DTCA
25
RUN
28
TEST
5
ILIM
19
FREQ
3
DRVSET
26
MODE
2
DRVUV
27
DRVCC
8
INTVCC
11
EXTVCC
10
VIN
7
BGUP
12
BGDN
13
BOOST
14
SW
15
TGDN
16
TGUP
17
PGOOD
18
TRACK/SS
4
ITH
20
VFB
21
SENSE+
22
SENSE-
23
GND
29
VPRG
6
VMID
9
CIN9
10uF
1210
100V
R13
2.2
+
COUT7
150uF
7343
16V
R5
1M
CIN11
10uF
1210
100V
+
CIN1
47uF
80V
12
TP1
E16
RUN
RS1 0.0015
2512
R18
604k
R2 0
L2
1 2
VFB
BOOST
SW
SENSE+
SENSE-
8
DEMO MANUAL DC2995A
Rev. A
ANALOG DEVICES, INC. 2022
08/22
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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