DC2660A Demo Manual Datasheet by Analog Devices Inc.

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ANALOG L POWER EY DEVICES ‘ D LINEAR“ DEMO MANUAL DC2660A
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DEMO MANUAL DC2660A
DESCRIPTION
LT8646S
65V, 8A Synchronous
Step-Down Silent Switcher 2
Demonstration circuit 2660A is a 65V, 8A synchronous
step-down second generation Silent Switcher
®
with
spread spectrum frequency modulation featuring the
LT
®
8646S. The demo board is designed for 5V output
from a 5.6V to 65V input. The wide input range allows
a variety of input sources, such as automotive batter-
ies and industrial supplies. The LT8646S is a compact,
ultralow emission, high efficiency, and high speed syn-
chronous monolithic step-down switching regulator. The
integrated bypass capacitors optimize all the fast current
loops and make it easier to minimize EMI/EMC emissions
by reducing layout sensitivity. Selectable spread spectrum
mode can further improve EMI/EMC performance. Fast
minimum on-time of 40ns enables high VIN to low VOUT
conversion at high frequency.
The LT8646S switching frequency can be programmed
either via oscillator resistor or external clock over a
200kHz to 2.2MHz range. The default frequency of demo
circuit 2660A is 2MHz. The SYNC pin on the demo board
is grounded (JP1 at BURST position) by default for low
ripple burst mode operation. To synchronize to an external
clock, move JP1 to SYNC and apply the external clock
to the SYNC terminal. Spread spectrum mode and pulse
skipping mode can be selected respectively by moving
JP1 shunt. Figure1 shows the efficiency of the circuit at
12V input and 24V input in Burst Mode Operation (input
from VIN terminal to bypass the EMI filter). Figure2
shows the LT8646S temperature rising on DC2660A
demo board under different load conditions. The rated
All registered trademarks and trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
maximum load current is 8A, while derating is neces-
sary for certain input voltage and thermal conditions. Low
switching frequency can extend the output load capability
by reducing the power dissipations. Figure3 shows the
temperature rising at 500kHz switching frequency.
The demo board has an EMI filter installed. The EMI
performance of the board (with EMI filter) is shown on
Figure4. The red line in Radiated EMI Performance is
CISPR25 Class 5 peak limit. The figure shows that the
circuit passes the test with a wide margin. To achieve EMI/
EMC performance as shown in Figure4, the input EMI
filter is required and the input voltage should be applied
at VEMI terminal. An inductor can be added in the EMI
filter to further reduce the conducted emission. The EMI
filter can be bypassed by applying the input voltage at
VIN terminal.
The LT8646S data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this demo manual
for demo circuit 2660A. The LT8646S is assembled in a
6mm × 4mm LQFN package with exposed pads for low
thermal resistance. The layout recommendations for low
EMI operation and maximum thermal performance are
available in the data sheet section Low EMI PCB Layout
and Thermal Considerations.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2660A
Specifications are at TA = 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN_EMI Input Supply Range with EMI Filter 5.6 65 V
VOUT Output Voltage 4.85 5 5.15 V
IOUT Maximum Output Current Derating is Necessary for Certain VIN and
Thermal Conditions
8 A
fSW Switching Frequency 1.85 2 2.15 MHz
EFF Efficiency VIN = 12V , IOUT = 4A 93.8 %
mm 54 95 3:4chch 55 an ax : as 40 g E E 5 an 32 g m 75 POWER LOSS 24% 7n I6 55 sz na SVNC/MODE=GND an n 4 2 a 4 5 e 7 a LOAD CURRENT (A) um um so an so an 5 m g m E 50 E 50 I I a 5a a 50 § 35 3‘ 40 § an E —\ :34 E m mm m z 3" —"nur=GA : 3" 3 2o - -\W:4A 2 20 w m u 0 I2 43 24 an as 42 4a 54 an 42 u; 24 an as 42 4a 54 so WPUT VOLTAGE (v) WPUT VOLTAGE (V)
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DEMO MANUAL DC2660A
DESCRIPTION
Figure1. LT8646S Demo Circuit DC2660A Efficiency
vs Load Current (Input from VIN Terminal)
Figure2. LT8646S Demo Circuit DC2660A Case Temperature
Rising vs Input Voltage (2MHz)
Figure3. LT8646S Demo Circuit DC2660A Case Temperature
Rising vs Input Voltage (500kHz)
POWER LOSS
VOUT = 5V
fSW = 2MHz
SYNC/MODE = GND
EFFICIENCY
V
IN
=12V
V
IN
=24V
LOAD CURRENT (A)
60
65
70
75
80
85
90
95
100
0.8
1.6
2.4
3.2
4.0
4.8
5.6
6.4
EFFICIENCY (%)
POWER LOSS (W)
DC2660A F01
I
OUT
= 8A
I
OUT
= 6A
I
OUT
= 4A
INPUT VOLTAGE (V)
12
18
24
30
36
42
48
54
60
0
10
20
30
40
50
60
70
80
90
100
CASE TEMPERATURE RISING (°C)
DC2660A F02
VOUT = 5V
fSW = 2MHz
I
OUT
= 8A
I
OUT
= 6A
I
OUT
= 4A
INPUT VOLTAGE (V)
12
18
24
30
36
42
48
54
60
10
20
30
40
50
60
70
80
90
100
CASE TEMPERATURE RISING (°C)
DC2660A F03
VOUT = 5V
fSW = 500kHz
FREQUENCY (MHZ) FREQUENCY (MHZ) FREQUENCY (MHZ)
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DEMO MANUAL DC2660A
DESCRIPTION
Figure4. LT8646S Demo Circuit DC2660A EMI Performance
(14V Input from VEMI, with EMI filter, IOUT = 4A)
(WITH EMI FILTER INSTALLED)
14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz
(WITH EMI FILTER INSTALLED)
14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz
DC2660A F04a
DC2660A F04b
DC2660A F04c
Conducted EMI Performance
Radiated EMI Performance
(CISPR25 Radiated Emission Test with Class 5 Peak Limits)
VERTICAL POLARIZATION
PEAK DETECTOR
FREQUENCY (MHz)
FREQUENCY (MHz)
–5
10
15
20
25
30
35
40
45
50
–30
–20
–10
10
20
30
40
50
60
–5
10
15
20
25
30
35
40
45
50
0 100 200 300 400 500 600 700 800 900 1000
0 3 6 9 12 15 18 21 24 27 30
FREQUENCY (MHz)
0 100
AMPLITUDE (dBµV/m) AMPLITUDE (dBµV/m) AMPLITUDE (dBµV)
200 300 400 500 600 700 800 900 1000
HORIZONTAL POLARIZATION
PEAK DETECTOR
CLASS 5 PEAK LIMIT
SPREAD SPECTRUM MODE
FIXED FREQUENCY MODE
CLASS 5 PEAK LIMIT
SPREAD SPECTRUM MODE
FIXED FREQUENCY MODE
FIXED FREQUENCY MODE
SPREAD SPECTRUM MODE
. LT86465 . 65V. BA SYNCHRONOUS . STEP_DOWMDEHZ-EQEASWITCHER 2 *SEE awn “mm 0 VOUT QM] {NI/EH a a 5m 3° EMI GND ELEV/div O :0 ANALOG av gm" DEVICES spmiéé‘cfififig mew g EURSY InJinmv cam/55555 1m) 4524mm , m E" CLKOUT GND "‘5 vc swc PG EMS O o o o 0 0g 0 O
4
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DEMO MANUAL DC2660A
QUICK START PROCEDURE
Demonstration circuit 2660A is easy to set up to evalu-
ate the performance of the LT8646S. Refer to Figure5
for proper measurement equipment setup and follow the
procedure below:
NOTE: When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the output voltage ripple by
touching the probe tip directly across the output capaci-
tor. See Figure6 for the proper scope technique. Figure7
shows the output voltage ripple measured at the output
capacitor C9.
1. Place JP1 on BURST position.
2. With power off, connect the input power supply to
VEMI and GND. If the input EMI filter is not desired,
connect the input power supply to VIN and GND.
3. With power off, connect the load from VOUT to GND.
4. Turn on the power at the input.
NOTE: Make sure that the input voltage does not
exceed 65V.
5. Check for the proper output voltage (VOUT = 5V).
NOTE: If there is no output, temporarily disconnect
the load to make sure that the load is not set too high
or is shorted.
6. Once the proper output voltage is established, adjust
the load within the operating ranges and observe the
output voltage regulation, ripple voltage, efficiency
and other parameters.
7. An external clock can be added to the SYNC terminal
when SYNC function is used (JP1 on the SYNC posi-
tion). Please make sure that R2 should be chose to set
the LT8646S switching frequency equal to or below
the lowest SYNC frequency. JP1 can also set LT8646S
in spread spectrum mode (JP1 on the spread-spec-
trum position) or pulse skipping mode (JP1 on the
pulse-skipping position).
_EMI
Figure5. Proper Measurement Equipment Setup
// // [ AC COUPLED Wigme/HA‘A AMMMM “I ‘7 Y Y mans/u w
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DEMO MANUAL DC2660A
QUICK START PROCEDURE
Figure6. Measuring Output Ripple at Output Capacitor C9
Figure7. LT8646S Demo Circuit DC2660A Output Voltage Ripple
(12V Input, IOUT = 8A, Full BW)
DC2660A F07
500ns/DIV
VOUT
5mV/DIV
AC COUPLED
+
VOUT
GND
C9
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DEMO MANUAL DC2660A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C2, C12 CAP., X7R, 0.47µF, 100V, 10%, 0805 MURATA, GRM21BR72A474KA73L
2 1 C5 CAP., C0G, 330pF, 50V, 5%, 0603 MURATA, GRM1885C1H331JA01D
3 1 C6 CAP., X5R, 100µF, 10V, 20%, 1210 MURATA, GRM32ER61A107ME20L
4 1 C8 CAP., X7R, 0.1µF, 25V, 10%, 0603 MURATA, GRM188R71E104KA01D
5 1 C9 CAP., X5R, 10µF, 25V, 20%, 0603 MURATA, GRM188R61E106MA73D
6 1 C16 CAP., C0G, 4.7pF, 50V, ±0.25pF, 0603 MURATA, GRM1885C1H4R7CA01D
7 1 C17 CAP., X7S, 4.7µF, 100V, 10%, 1210 MURATA, GRJ32DC72A475KE11L
8 1 C20 CAP., X5R, 1µF, 16V, 10%, 0603 MURATA, GRM188R61C105KA12D
9 1 L1 INDUCTOR, 1.0µH, XEL6030 COILCRAFT, XEL6030-102MEC
10 2 R1, R5 RES., CHIP, 100k, 1/10W, 1%, 0603 VISHAY, CRCW0603100KFKEA
11 1 R2 RES., CHIP, 17.8k, 1/10W, 1%, 0603 VISHAY, CRCW060317K8FKEA
12 1 R3 RES., CHIP, 243k, 1/10W, 1%, 0603 VISHAY, CRCW0603243KFKEA
13 1 R4 RES., CHIP, 7.5k, 1/10W, 1%, 0603 VISHAY, CRCW06037K50FKEA
14 1 R7 RES., CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA
15 1 U1 I.C., 65V, 8A SYNC BUCK, 6mm × 4mm LQFN LINEAR TECH., LT8646SEV#PBF
Additional Demo Board Circuit Components
1 1 C1 CAP., ALUM 22µF, 100V, 20% SUNCON, 100CE22BS
2 2 C3,C10 CAP., X7R, 2.2µF, 100V, 10%, 1210 MURATA, GRM32ER72A225KA35L
3 1 C4 CAP., X7R, 0.1µF, 100V, 10%, 0603 MURATA, GRM188R72A104KA35D
4 1 C14 CAP., X5R, 0.1µF, 100V, 10%, 0402 MURATA, GRM155R62A104KE14D
5 0 C15, C18 (OPT) CAP., 0603
6 0 C19 (OPT) CAP., 1210
7 1 FB1 FERRITE BEAD, 0.006Ω 8A, 1812 WURTH ELEKTRONIK, 74279226101
8 0 R6 (OPT) RES., OPTION, 0603
9 1 R8 RES., CHIP, 0Ω, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA
Hardware: For Demo Board Only
1 9 E1, E5-E9, E11, E14-E15 TESTPOINT, TURRET, .094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 4 E2, E10, E12, E13 TESTPOINT, TURRET, .061" MILL-MAX, 2308-2-00-80-00-00-07-0
3 1 JP1 2×4, 2mm DOUBLE ROW HEADER WURTH ELEKTRONIK, 62000821121
4 1 XJP1 SHUNT, 2mm CENTER WURTH ELEKTRONIK, 60800213421
5 4 J1-J4 JACK BANANA KEYSTONE, 575-4
6 4 MH1-MH4 STAND-OFF, NYLON 0.50" TALL WURTH ELEKTRONIK, 702935000
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DEMO MANUAL DC2660A
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
ALL CAPACITORS ARE 0603.
NOTES: UNLESS OTHERWISE SPECIFIED
1.
ALL RESISTORS ARE 0603.
100CE22BS
SYNC
BURST
SPREAD-SPECTRUM
PULSE-SKIPPING
*
*
SEE DEMO MANUAL
R2
17.8K
E9
GND
FB1
74279226101 E11 EN
C2
0.47uF
100V
0805
E2
GND
R6
OPT
C17
4.7uF
100V
1210
C14
0.1uF
0402
100V
JP1
1 2
3
5
7
4
6
8
R8
0
E5
SYNC
E8 PG
C5
330pF
C12
0.47uF
100V
0805
J1
5.6V - 65V
C6
100uF
10V
1210
+
C1
22uF
100V
R3
243K
R7
1M
C3
2.2uF
1210
100V
J3
VOUT
5V / 8A
E7
TR/SS
E1
VIN
J4 GND
C16
4.7pF
C18
OPT
C20
1uF
16V
L1
1.0uH
XEL6030-102
C9
10uF
25V
C8
0.1uF
C15
OPT
E10
VEMI
C10
2.2uF
1210
100V
E6 CLKOUT
J2
R5
100K
E12
E14
VC
C4
0.1uF
100V
U1
LT8646S
VIN
4
EN
25
SYNC
28
VCC
2
RT
26
FB
32
PG
31
BIAS
1
BST
11
GND1
8
GND2
10
TR/SS
29
GND1
9
GND2
17
VIN
5
VIN
6
VIN
21
VIN
22
VIN
23
GND2
18
GND2
19
VC
30
CLKOUT
27
SW
12
SW
13
SW
14
SW
15
SW
16
NC
3
NC
7
NC
20
NC
24
GND
33
GND
34
GND
35
GND
36
GND
37
GND
38
GND
40
GND
41
C19
OPT
1210
E15 BIAS
E13
R4
7.50K
R1
100K
VIN
M ANALOG DEVICES
8
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DEMO MANUAL DC2660A
LT 0218 • PRINTED IN USA
ANALOG DEVICES, INC. 2018
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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