ANALOG DEVICES LT8640A Synchronous Step Down Silent Switcher User Manual

User Manual for ANALOG DEVICES models including: DC3099A, LT8640A Synchronous Step Down Silent Switcher, LT8640A, Synchronous Step Down Silent Switcher, Step Down Silent Switcher, Down Silent Switcher, Silent Switcher, Switcher

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dc3099a

DEMO MANUAL DC3099A

LT8640A 42V, 5A (8A Peak) Synchronous Step-Down Silent Switcher with 2.5µA Quiescent Current

DESCRIPTION

Demonstration circuit 3099A is a 42V, 5A synchronous step-down Silent Switcher® with spread spectrum frequency modulation featuring the LT®8640A. The demo board is designed for 5V output from a 5.7V to 42V input. Meanwhile the LT8640A can operate down to 3.4V inputs. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8640A is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic stepdown switching regulator. The integrated power switches and inclusion of all necessary circuitry reduce the components count and solution size. Special Silent Switcher architecture minimizes EMI emissions. Selectable spread spectrum mode can further improve EMI performance. Ultralow 2.5A quiescent current in Burst Mode® operation achieves high efficiency at very light loads. Fast minimum on-time of 30ns enables high VIN to low VOUT conversion at high frequency.
The LT8640A switching frequency can be programmed either via oscillator resistor or external clock over a

200kHz to 3MHz range. The default frequency of demo circuit 3099A is 2MHz. The LT8640A SYNC/MODE pin on the demo board is grounded (JP1 at BURST position) by default for low ripple Burst Mode operation. Spread spectrum mode and forced continuous mode can be selected respectively by moving JP1 shunt. To synchronize to an external clock, move JP1 to FCM/SYNC and apply the external clock to the SYNC terminal.
The LT8640A 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 3099A. The LT8640A is assembled in a 3mm × 4mm plastic QFN package with exposed pad 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 and Peak Output Current.
Design files for this circuit board are available.
All registered trademarks and trademarks are the property of their respective owners.

PERFORMANCE SUMMARY Specifications are at TA = 25°C

SYMBOL PARAMETER

CONDITIONS

MIN TYP MAX UNITS

VIN

Input Supply Range

5.7

VOUT

Output Voltage

R4 = 1M, R5 = 243k

4.85

5.15

IOUT

Maximum Continuous Output Current Derating Is Necessary for Certain VIN and Thermal Conditions 5

fSW

Switching Frequency

R2 = 17.8k, JP1 = FCM/SYNC

1.85

2.15

MHz

EFF

Efficiency at DC

VIN = 12V , IOUT = 3A

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DEMO MANUAL DC3099A

QUICK START PROCEDURE
Demonstration circuit 3099A is easy to set up to evaluate the performance of the LT8640A. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
1. Place JP1 on BURST position.
2. With power off, connect the input power supply to VEMI and GND. If the EMI performance is not important, the input EMI filter can be bypassed by connecting the input power supply to VIN and GND.
3. With power off, connect the load from VOUT to GND.
4. To read the input voltage and output voltage accurately, the voltage meters should be connected to VIN_SENSE and VOUT_SENSE turret pins.
5. Turn on the power at the input.
NOTE: Make sure that the input voltage does not exceed 42V.
6. 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.

7. 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.
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 capacitor. See Figure 2 for the proper scope technique.
8. JP1 can also set LT8640A in spread spectrum mode (JP1 on the SPREAD-SPECTRUM position) or forced continuous mode (JP1 on the FCM/SYNC position). An external clock can be added to the SYNC terminal when SYNC function is used (JP1 on the FCM/SYNC position). Please make sure that R2 should be chosen to set the LT8640A switching frequency equal to or below the lowest SYNC frequency.

Figure 1. Proper Measurement Equipment Setup

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DEMO MANUAL DC3099A

QUICK START PROCEDURE
Figure 3 shows the efficiency of demo circuit 3099A at 12V input and 24V input in Burse Mode Operation (input from VIN terminal, JP1 = BURST).
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 Figure 4 is CISPR25 Class 5 peak limit. The figure shows that the circuit passes the test with a wide margin. To achieve EMI performance as shown in Figure 4, the input EMI filter is required, and the input voltage should be applied at VEMI.

+ VOUT C13
GND

Figure 2. Measuring Output Ripple at Output Capacitor C13

100 EFFICIENCY
95

4.0 VIN = 12V VIN = 24V 3.5

3.0

EFFICIENCY (%)

POWER LOSS (W)

2.5

2.0

1.5

POWER LOSS

1.0

VOUT = 5V fSW = 2MHz

0.5

JP1 = BURST 0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

LOAD CURRENT (A)

dc3099a F03

Figure 3. LT8640A Demo Circuit 3099A Efficiency vs Load Current (Input from VIN Terminal)

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DEMO MANUAL DC3099A

QUICK START PROCEDURE

AMPLITUDE (dBµV)

Conducted EMI Performance CISPR25 Conducted Emission Test with Class 5 Peak Limits)
60 VOLTAGE METHOD
50

CLASS 5 PEAK LIMIT

SPREAD SPECTRUM MODE

FIXED FREQUENCY MODE

9 12 15 18 21 24 27 30

FREQUENCY (MHz) DC3099A DEMO BOARD (WITH EMI FILTER INSTALLED) 12V INPUT TO 5V OUTPUT AT 5A, fSW = 2MHz

dc3099a F04a

AMPLITUDE (dBµV/m)

Radiated EMI Performance (CISPR25 Radiated Emission Test with Class 5 Peak Limits)

50 VERTICAL POLARIZATION
45 PEAK DETECTOR 40

CLASS 5 PEAK LIMIT

SPREAD SPECTRUM MODE

FIXED FREQUENCY MODE 0
0 100 200 300 400 500 600 700 800 900 1000

FREQUENCY (MHz)

dc3099a F04b

50 HORIZONTAL POLARIZATION
45 PEAK DETECTOR 40

CLASS 5 PEAK LIMIT

SPREAD SPECTRUM MODE

FIXED FREQUENCY MODE 0

0 100 200 300 400 500 600 700 800 900 1000

FREQUENCY (MHz) DC3099A DEMO BOARD (WITH EMI FILTER INSTALLED) 12V INPUT TO 5V OUTPUT AT 5A, fSW = 2MHz

dc3099a F04c

AMPLITUDE (dBµV/m)

Figure 4. LT8640A Demo Circuit 3099A EMI Performance (12V Input from VEMI, with EMI filter, IOUT = 5A)

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DEMO MANUAL DC3099A

PARTS LIST

ITEM QTY REFERENCE

Required Circuit Components

2 C2, C12

2 C4, C8

1 C5

1 C6

2 C7, C9

1 C11

1 C13

1 L1

2 R1, R3

1 R2

1 R4

1 R5

1 U1

Additional Demo Board Circuit Components

1 C1

2 C3, C10

1 C14

0 C19 (OPT)

1 FB1

0 L2

1 Q1

0 R6 (OPT)

2 R7, R12

1 R10

1 R11

PART DESCRIPTION
CAP., X5R, 1F, 50V, 10%, 0603 CAP., X7R, 0.1F, 16V, 10%, 0603 CAP., C0G, 10pF, 25V, ±0.25pF, 0603 CAP., X5R, 100F, 10V, 20% 1210 CAP., X7R, 1F, 25V, 10%, 0603 CAP., X5R, 10F, 50V, 10%, 1206 CAP., X5R, 4.7F, 25V, 10%, 0603 INDUCTOR, 1.5H RES., CHIP, 100k, 1/10W, 1% 0603 RES., CHIP, 17.8k, 1/10W, 1% 0603 RES., CHIP, 1M, 1/10W, 1%, 0603 RES., CHIP, 243k, 1/10W, 1%, 0603 I.C., STEP-DOWN SILENT SWITCHER, QFN-18
CAP., ALUM 22F, 63V CAP., X7R, 10F, 50V, 10%, 1210 CAP., X7R, 0.1F, 50V, 10%, 0402 CAP., OPTION, 0805 BEAD, FERRITE, 100 AT 100MHz, 8A, 1812 IND., OPT, XAL60XX MOSFET, N-CH, 40V, 14A, DPAK (TO-252) RES., OPTION, 0603 RES., CHIP, 0, 1/10W, 1%, 0603 RES., CHIP, 10k, 1/10W, 1% 0603 RES., 0.1, 1%, 3W, 2512, SHORT-SIDE TEMINAL

MANUFACTURER/PART NUMBER
MURATA, GRT188R61H105KE13D MURATA, GRM188R71C104KA01D AVX, 06033A100CAT2A MURATA, GRM32ER61A107ME20L MURATA, GRM188R71E105KA12D TDK, C3216X5R1H106K160AB MURATA, GRM188R61E475KE11D COILCRAFT, XEL6030-152ME VISHAY, CRCW0603100KFKEA VISHAY, CRCW060317K8FKEA VISHAY, CRCW06031M00FKEA VISHAY, CRCW0603243KFKEA ANALOG DEVICES, LT8640AJUDCM#PBF
SUN ELECT., 63CE22BS MURATA, GRM32ER71H106KA12L MURATA, GRM155R71H104KE14D
WURTH ELEKTRONIK, 74279226101
VISHAY, SUD50N04-8M8P-4GE3
VISHAY, CRCW06030000Z0EA VISHAY, CRCW060310K0FKEA SUSUMU, KRL3264E-C-R100-F-T1

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DEMO MANUAL DC3099A

PARTS LIST

Hardware: For Demo Board Only

9 E1, E5-E9, E15-E17

4 E2, E3, E4, E10

4 J1-J4

1 JP1

4 MP1-MP4

1 XJP1

TESTPOINT, TURRET, 0.094" TESTPOINT, TURRET, 0.064" JACK BANANA 2X3, 0.079 DOUBLE ROW HEADER STANDOFF, NYLON, SNAP-ON, 11.1mm SHUNT, 0.079" CENTER

MILL-MAX, 2501-2-00-80-00-00-07-0 MILL-MAX, 2308-2-00-80-00-00-07-0 KEYSTONE, 575-4 WURTH ELEKTRONIK, 62000621121 WURTH ELEKTRONIK, 702934000 WURTH ELEKTRONIK, 60800213421

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SCHEMATIC DIAGRAM

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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.

VIN_SENSE

** C2 SHOULD BE PLACED BETWEEN VIN1 AND GND1. C12 SHOULD BE PLACED BETWEEN VIN2 AND GND2. THESE CAPACITORS MUST BE PLACED AS CLOSE AS POSSIBLE TO LT8640A.

U1 LT8640A

E2
VIN E1
D

VIN R1 100k
R6 OPT

C1 + 22uF
63V SUNCON 63CE22BS

C11 10uF 50V 1206

4 VIN1

C2 1uF

50V

VIN2

C12 1uF

50V

EN/UV E6
SYNC E5

JP1

FCM/SYNC 1

BURST 3

SPREAD-SPECTRUM 5

GND E9
C
TR/SS

14 EN/UV

17 SYNC

2 INTVCC

16 TR/SS

1uF

25V

15 RT

R2 17.8k (2MHz)

GND1

0.1uF

10 11

GND1 GND2 GND2

18 GND

* SEE DEMO MANUAL

3 BST SW 8
9 SW
21 SW

0.1uF

16V

1.5uH

XEL6030-152MEB

VOUT C6 100uF 10V 1210

VOUT_SENSE

VOUT

* 5V/5A

C9 C13 1uF 4.7uF

1 BIAS
PG 19 FB 20

R7 0
R12 0 R4 1M

J4 GND
E4

C
R5 243k C5 10pF
R3 100k

VEMI

5.7V - 42V

FB1 74279226101

2 VIN

C14 0.1uF 50V 0402

C3 10uF 50V 1210

C10 10uF 50V 1210

L2 OPT

B
GND E10
J2

PG E8

VOUT

C19 OPT 0805

Q1 SUD50N04-8m8P

E15

PULSE_GEN

R10

10k

E16 R11 0.100 2512,SHORT-SIDE E17

LOAD_STEP GND

OPTIONAL TRANSIENT RESPONSE CIRCUIT

DEMO MANUAL DC3099A

CUSTOMER NOTICE

APPROVALS

ANALOG

2555 AUGUSTINE DRIVE

NOTES: UNLESS OTHERWISE SPECIFIED

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

PCB DES. APP ENG.

NAME NAME

DEVICES
AHEAD OF WHAT'S POSSIBLE TM

SANTA CLARA, CA 95054
A
www.analog.com

1. ALL RESISTORS ARE 0603. ALL CAPACITORS ARE 0603.

OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE

TITLE: SCHEMATIC 42V, 5A (8A PEAK) SYNCHRONOUS

OR RELIABILITY. CONTACT ANALOG DEVICES APPLICATIONS ENGINEERING FOR ASSISTANCE.

STEP-DOWN SILENT SWITCHER WITH 2.5uA QUIESCENT CURRENT

IC NO.

LT8640A

SCHEMATIC NO. AND REVISION:

THIS CIRCUIT IS PROPRIETARY TO ANALOG DEVICES AND SUPPLIED FOR USE WITH ANALOG DEVICES PARTS.

SKU NO. DC3099A

710-DC3099A_REV03

SIZE: N/A DATE: Friday, February 18, 2022

SHEET 1 OF 2

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DEMO MANUAL DC3099A

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.
Legal Terms and Conditions
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www.analog.com
ANALOG DEVICES, INC. 2022

References