1
DEMO MANUAL DC2786A
Rev. 0
DESCRIPTION
LTC7800
Low Quiescent Current High Frequency
Step-Down Converter
Demonstration circuit 2786A is a single output non-
isolated synchronous step-down converter that drives
an all N-channel MOSFET power stage. It features the
LTC
®
7800, a low quiescent current high frequency (pro-
grammable fixed frequency from 320kHz up to 2.25MHz)
synchronous step-down DC/DC controller housed in a
small 3mm x 4mm QFN package.
This DC2786A operates over an input voltage range from
8V to 40V, while the LTC
®
7800 can operate up to 60V. This
demo board produces a 3.3V output voltage with up to
10A output current, and is configured with a sense resistor
for current sensing. A mode selector allows the DC2786A
All registered trademarks and trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
BOARD PHOTO
to operate in forced continuous operation, pulse-skipping
or Burst Mode
®
operation during light loads.
The LTC7800 features two integrated 5V gate drivers with
20ns deadtime which is good for GaN transistors or logic-
level MOSFETs to maximize efficiency. The EXTVCC pin
permits the LTC7800 to be powered from the output of
the switching regulator or other available source, reducing
power dissipation and improving efficiency. Please refer
to the LTC7800 data sheet for a complete description of
the part operation and application information.
Design files for this circuit board are available.
Specifications are at TA = 25°C
Figure1. LTC7800; 10A DC2786A Demo Circuit
PARAMETER CONDITIONS VALUE UNITS
Input Voltage Range 8 to 40 V
Output Voltage, VOUT VIN = 8-40V, IOUT = 0A to 10A 3.3 V
Maximum Output Current, IOUT VIN = 8-40V, VOUT = 3.3V 10 A
Typical Efficiency VIN = 12V, VOUT = 3.3V, IOUT = 10A 88.6 %
Peak Efficiency VIN = 12V, VOUT = 3.3V 89 %
Switching Frequency 2 MHz
Note 1: 200LFM forced airflow is required for VIN > 24V
2
DEMO MANUAL DC2786A
Rev. 0
QUICK START PROCEDURE
Demonstration circuit 2786A is easy to set up to evaluate
the performance of the LTC7800. Refer to Figure2 for
the proper measurement equipment setup and follow the
procedure below.
1. With power off, connect the input power supply to VIN
(8V-40V) and GND (input return).
2. Connect the output loads between VOUT and GND
(Initial load: no load). Refer to Figure 2.
NOTE: Please use J1, J2 (Not E2, E4) and J3, J4 (Not E5,
E7) for input power supply and output load connection.
3. Connect the DVMs to the input and output.
4. Check the default jumper/switch position: JP2 (RUN): OFF
5. Turn on the input power supply and adjust voltage to 12V;
NOTE. Make sure that the input voltage does not exceed 40V.
6. Turn on the switches: JP2: ON.
7. Check for the proper output voltages from VOUT to GND.
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 Figure3 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.
External EXTVCC Option
The EXTVCC pin of the LTC7800 on the DC2786A board
can be utilized for better efficiency and better thermal per-
formance. Please follow the below procedure if an exter-
nal power supply is used to bias the LTC7800 EXTVCC pin
(Do not float this pin).
1. Populate R24 with a 0Ω resistor.
2. Apply a DC voltage (recommend 6V – 13V) on EXTVCC
and GND turret after the input voltage is established.
Make sure EXTVCC < VIN.
3. Turn off the DC bias on the EXTVCC before powering
off the input power supply.
7
DEMO MANUAL DC2786A
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 CIN1 CAP., 56uF 63V 13X13 SUNCON, 63HVH56M
2 1 CIN2 CAP., 0805 1uF 10% 100V X7S MURATA, GRM21BC72A105KE01L
3 2 CIN3, CIN4 CAP., 1210 10uF 10% 100V X7S MURATA, GRM32EC72A106KE05L
4 3 COUT1, COUT2, COUT4 CAP, 1206 100uF 10% 6.3V X5R MURATA, GRM31CR60J107KE39L
5 4 C1, C2, C7, C9 CAP, 0603 0.1uF 10% 100V X7S TDK, C1608X7S2A104K080AB
6 2 C4, C14 CAP, 0603 1uF 20% 25V X7R TDK, C1608X7R1E105M080AE
7 1 C5 CAP, 0603 2.2uF 10% 10V X7R MURATA, GRM188R71A225KE15D
8 1 C6 CAP, 0603 470pF 5% 50V C0G/NP0 AVX, 06035A471JAT2A
9 1 C8 CAP, 0603 100pF 5% 50V C0G/NPO AVX, 06035A101JAT2A
10 1 C10 CAP, 0603 4.7pF 5% 25V COG AVX, 06033A4R7DAT2A
11 1 C11 CAP, 0603 27pF 10% 50V C0G AVX, 06035A270KAT2A
12 1 C13 CAP, 0603 4700pF 10% 50V X7R AVX, 06035C472KAT2A
13 1 C15 CAP, 0603 10uF 10V TDK, C1608X5R1A106K080AC
14 1 D1 DIODE, SCHOTTKY 100V POWERDI123 DIODES INC., DFLS1100-7
15 1 L2 IND., 0.33uH COILCRAFT, XAL5030-331MEB
16 1 Q1 POWER MOSFET INFINEON, BSC094N06LS5ATMA1
17 1 Q3 POWER MOSFET INFINEON, BSC065N06LS5
18 1 RS1 RES, 0805 0.004 SUSUMU, KRL2012E-C-R004-F-T5
19 1 R3 RES, 0603 2.2 OHMS 5% VISHAY, CRCW06032R20JNEA
20 3 R4, R12, R18 RES, 0603 0 OHM JUMPER VISHAY, CRCW06030000Z0EA
21 4 R6, R9, R15, R22 RES, 0603 100K OHMS 1% VISHAY, CRCW0603100KFKEA
22 1 R8 RES, 0603 1K OHMS 5% VISHAY, CRCW06031K00JNEA
23 1 R10 RES, 0603 49.9 OHMS 1% VISHAY, CRCW060349R9FKEA
24 1 R14 RES., 1M, 1%, 0603 NIC, NRC06f1004TRF
25 1 R17 RES, 0603 100 OHMS 1% VISHAY, CRCW0603100RFKEA
26 1 R19 RES, 0603 511K OHMS 1% VISHAY, CRCW0603511KFKEA
27 1 R20 RES, 0603 6.81K OHMS 1% VISHAY, CRCW06036K81FKEA
28 1 R21 RES, 0603 162K OHMS 1% VISHAY, CRCW0603162KFKEA
29 1 R25 RES, 0603 1 OHMS 1% VISHAY, CRCW06031R00FKEA
30 1 U1 IC., LTC7800, QFN ANALOG DEVICES, LTC7800EUDC#PBF
Additional Demo Board Circuit Components
1 0 CIN5 CAP., 0805, OPTION
2 0 CIN6 CAP., 1210, OPTION
3 0 COUT3 CAP., 1206, OPTION
4 0 COUT5 CAP., 7343, OPTION
5 0 C3, C12 CAP., 0603, OPTION
6 0 L1 IND., High Current Inductor, OPTION WURTH, WE7443630420
7 0 Q2, Q4 XSTR, POWER MOSFET., OPTION
8 0 R16, R24, R1, R2, R5, R7, R11 RES., 0603, OPTION
9 0 R13 RES., 0805, OPTION
8
DEMO MANUAL DC2786A
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Hardware: For Demo Board Only
1 9 E1, E2, E3, E4, E5, E6, E7, E8, E9 TESTPOINT, TURRET, .095" MILL-MAX, 2501-2-00-80-00-00-07-0
2 1 JP1 2MM DOUBLE ROW HEADER, 3X2 SAMTEC, TMM-103-02-L-D
3 1 JP2 HEADER, 3 PIN 0.079 SINGLE ROW SULLINS, NRPN031PAEN-RC
4 4 J1, J2, J3, J4 STUD, TESTPIN PEM, KFH-032-10
5 8 J1, J2, J3, J4 NUT, BRASS 10-32 ANY, #10-32
6 4 J1, J2, J3, J4 RING, LUG #10 KEYSTONE, #10
7 4 J1, J2, J3, J4 WASHER, TIN PLATED BRASS ANY, #10
8 1 XJP1, XJP2 SHUNT, 2mm SAMTEC, 2SN-BK-G
9 4 MH1, MH2, MH3, MH4 STANDOFF, NYLON, SNAP-ON, 0.375" KEYSTONE, 8832
9
DEMO MANUAL DC2786A
Rev. 0
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
BURST MODE
CCM
MODE
PULSE SKIP
25kohm, 320kHz
34kohm, 500kHz
57.6kohm, 1MHz
100kohm, 2.1MHz
14V max
ILIM = GND, 30mV
ILIM = INTVCC, 50mV
ILIM = FLOAT, 75mV
XAL5030-331ME
GND
VOUT
VIN+
STEP-DOWN CONVERTER
WE7443630420
PRODUCTION1 3-16-18
INTVCC2
EXTVCC2
VIN2
VIN2
VOSP2
INTVCC2 INTVCC2
INTVCC2
VOSP2
EXTVCC2
INTVCC2
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
YL
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
YL
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
YL
DATE:
SHEET OF
TITLE: SCHEMATIC
APPROVALS
PCB DES.
APP ENG.
Phone: (408)432-1900
www.linear.com
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.
11
HZ
Y.LIU
LTC7800EUDC
LOW QUIESCENT CURRENT HIGH FREQUENCY
DC2786A
DC2786A_REV01
N/A DATE:
SHEET OF
TITLE: SCHEMATIC
APPROVALS
PCB DES.
APP ENG.
Phone: (408)432-1900
www.linear.com
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.
11
HZ
Y.LIU
LTC7800EUDC
LOW QUIESCENT CURRENT HIGH FREQUENCY
DC2786A
DC2786A_REV01
N/A DATE:
SHEET OF
TITLE: SCHEMATIC
APPROVALS
PCB DES.
APP ENG.
Phone: (408)432-1900
www.linear.com
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.
11
HZ
Y.LIU
LTC7800EUDC
LOW QUIESCENT CURRENT HIGH FREQUENCY
DC2786A
DC2786A_REV01
N/A
E8
PGOOD
C5 2.2uF
E10
GND
L1 OPT
R4 0
R9
100K
U1
LTC7800
INTVCC 14
TG
10
SGND
3
FREQ 20
PGOOD
9
RUN
4
SENSE1-
5
SGND
21
BG 13
BOOST 12
SENSE1+
6
PGND 16
PLLIN/MODE
1
EXTVCC 15
VIN 17
TRACK/SS 19
VFB
7
8
ITH
ILIM 18
SGND
2
SW 11
COUT3
OPT
1206
R7
OPT
J4
GND
R16
OPT
E9
EXTVCC
D1
DFLS1100
C12
OPT
J3
VOUT
3.3V, 10A
E7
C3
OPT
COUT4
100uF
6.3V
1206
C11
27pF
E2
R15
100k
+
COUT5
OPT
16V
7343
R24
OPT
R18
0
R20
6.81K
CIN2
1uF
100V
0805
C6
470pF Q4
OPT
3
1 5
2
4
6
7
8
R12
0
R19
511k
C7
0.1uF
R17
100
CIN4
10uF
100V
1210
CIN5
OPT
100V
0805
Q1
BSC094N06LS5
3
1 5
2
4
6
7
8
CIN3
10uF
100V
1210
C15 10uF
C13
4700pF
R14
1M
Q3
BSC065N06LS5
3
1 5
2
4
6
7
8
E3
SYNC
R3
2.2
E5
CIN6
OPT
100V
1210
E4
GND
J2
GND
COUT1
100uF
6.3V
1206
+
CIN1
56uF
63V
Q2
OPT
3
1 5
2
4
6
7
8
R11
OPT
J1
VIN
8V-40V
E6
RUN
RS1
0.004
0805B
R22
100K
JP1
1
3
2
4
56
R10
50
1%
JP2
ON
OFF
RUN
1
3
2
R21
162k
R25
1
C8
100pF
C1
0.1uF
C9
0.1uF
R8 1K
C4 1uF
R5
OPT
R1
OPT
R13
OPT
C2
0.1uF
100V
R2
OPT
E1
TRK / SS
C14
1uF
16V
R6
100k
COUT2
100uF
6.3V
1206
L2 0.33uH
C10
4.7pF
SENSE2+
SENSE2-
VIN2
SENSE2-
SENSE2+
VOUT2
10
DEMO MANUAL DC2786A
Rev. 0
ANALOG DEVICES, INC. 2020
05/20
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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