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dc2019bfb

DEMO MANUAL DC2019B

DESCRIPTION

LT8614

42V, 4A Micropower

Synchronous Step-Down

Silent Switcher

Demonstration circuit 2019B is a 42V, 4A micropower

synchronous step-down Silent Switcher™ featuring the

LT®8614. The demo board is designed for 5V output

from a 5.8V to 42V input. The wide input range allows a

variety of input sources, such as automotive batteries and

industrial supplies. The LT8614 is a compact, ultralow

emission, high efficiency and high speed synchronous

monolithic step-down 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/EMC emis-

operation achieves high efficiency at very light loads. Fast

conversion at high frequency.

TheLT8614switchingfrequencycanbeprogrammedeither

via oscillator resistor or external clock over a 200kHz to

3MHzrange.TheSYNCpinonthedemoboardisgrounded

by default for low ripple Burst Mode operation. To syn-

chronize to an external clock, move JP1 to SYNC and

apply the external clock to the SYNC turret. Once JP1 is

on SYNC position, a DC voltage of higher than 3V can be

applied to the SYNC turret for pulse-skipping operation.

Figure 1 shows the efficiency of the circuit at 12V input in

L

, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks

and Silent Switcher is a trademark of Linear Technology Corporation. All other trademarks are

the property of their respective owners.

PERFORMANCE SUMMARY

shows the LT8614 temperature rising on DC2019B demo

boardunderdifferentloadconditions.Theratedmaximum

load current is 4A, while derating is necessary for certain

ThedemoboardhasanEMIfilterinstalled.TheEMIperfor-

mance of the board (with EMI filter) is shown in Figure 3.

The red line in Figure 3 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 3, the input EMI filter is required and the input

The LT8614 data sheet gives a complete description of the

part,operationandapplicationinformation.Thedatasheet

must be read in conjunction with this demo manual for

demo circuit 2019B. The LT8614 is assembled in a 3mm

× 4mm plastic QFN package with exposed pads for low

thermalresistance.Properboardlayoutisessentialforboth

low EMI operation and maximum thermal performance.

See the data sheet sections, “Low EMI PCB Layout” and

“High Temperature Considerations.”

Design files for this circuit board are available at

http://www.linear.com/demo/DC2019B

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Input Supply Range

5.8

42

V

Output Voltage

4.85

5

5.15

V

Maximum Output Current

Thermal Conditions

4

A

Switching Frequency

1.85

2

2.15

MHz

Efficiency at DC

91.3

%