Linear Technology Analog Devices LT8608B Quick Start Manual

DESCRIPTION
Demonstration circuit 2521A is a 42V, 1.5A micropower
synchronous step-down regulator featuring the
LT8608B. There are two assembly versions. DC2521A-A
is for the LT8608 and DC2521A-B is for the LT8608B.
The LT8608/LT8608B is a compact, high efficiency, high
speed synchronous monolithic step-down switching
regulator. Top and bottom power switches, compensa-
tion components and other necessary circuits are inside
of the 2mm × 2mm DFN package to minimize external
components and simplify design. The difference LT8608
and LT8608B is the LT8608 works under low ripple
Burst Mode operation at light load condition, while the
®
LT8608B has pulse-skipping mode for light load. Due
to the Burst Mode operation, LT8608 consumes only
1.7μA of quiescent current when output is regulated at
5V. LT8608B has higher quiescent current because of its
pulse-skipping mode operation.
PERFORMANCE SUMMARY
SYMBOL PARAMETER
V Input Voltage Range
IN
V Output Voltage
OUT
I Maximum Output Current
OUT
f Switching Frequency
SW
EFE Efficiency at DC
DEMO MANUAL DC2521A
Synchronous Step-Down Regulator
The demo board is designed for 5V output from a 5.5V
LT8608/ to 42V input. The wide input range allows a variety of
input sources, such as automotive batteries and industrial
supplies.
The demo board has an EMI filter installed. The radiated
EMI performances of the board (with EMI filter) are shown
in Figure 2 and Figure 3. The red lines in Figure 2 and
Figure 3 are CISPR 25 Class 5 peak limit. To use the EMI
filter, the input should be tied to V
tor L2, which is a 0Ω jumper on the board by default
now, can be added in the EMI filter to further reduce the
conducted emission.
The LT8608 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 DC2521A.
Design files for this circuit board are available.
All registered trademarks and trademarks are the property of their respective owners.
Specifications are at T
CONDITIONS
V = 12V, I = 0.75A
IN OUT
LT8608/LT8608B
42V, 1.5A Micropower
= 25°C
A
MIN TYP
5.5
4.8 5
1.5
1.85 2
92
, not V . An induc-
EMI IN
MAX UNITS
42 V
5.2 V
A
2.15 MHz
%
UG-1403 Rev. 0
1