1
DC3054A-B
Rev. 0
DESCRIPTION
LTC3308B
3.3V to 1.8V at 4A, 6.6MHz Low EMI
Buck Regulator in a 0.47cm
2
Solution
Demonstration circuit 3054A-B features the
5V, 4A synchronous step-down Silent Switcher
®
oper-
ating as a 6.6MHz, 3.3V to 1.8V 4A buck regulator. The
LTC3308B supports adjustable output voltages from
0.5V to V
IN
, and operating frequencies from 3MHz up to
10MHz. The LTC3308B is a compact, ultralow emission,
high efficiency, and high speed synchronous monolithic
step-down switching regulator. A minimum on-time of
22ns enables high V
IN
to low V
OUT
conversion ratios at
high switching frequencies.
The DC3054A-B operating mode may be selected as
Burst Mode
®
operation, skip or forced continuous (FC)
mode. Setting JP1 to the FC/SYNC position will allow the
LTC3308B to sync to a clock frequency from 3MHz to
10MHz. The LTC3308B operates in forced continuous
mode when syncing to an external clock. The DC3054A-B
is set to a fixed 6.6MHz.
The DC3054A-B is set to a fixed 6.6MHz frequency by
connecting RT to V
IN
through a 0Ω resistor, R9. The fre-
quency can be easily changed by removing R9 and setting
an appropriate resistor in the R4 location to obtain the
desired frequency. Refer to the LTC3308B data sheet for
the proper R
T
value for a desired switching frequency.
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PERFORMANCE SUMMARY
The DC3054A-B also has an EMI filter to reduce conducted
EMI. This EMI filter can be included by applying the input
voltage at the V
IN
EMI terminal. The EMI performance
of the board is shown in the EMI Test Results section.
The red lines in the EMI performance graphs illustrate
the CISPR25 Class 5 peak limits for the conducted and
radiated emission tests.
The LTC3308B data sheet gives a complete description
of the device, operation and application information. The
data sheet must be read in conjunction with this demo
manual. The LTC3308B is assembled in a 2mm × 2mm
LQFN package with exposed pads for low thermal resis-
tance. The layout recommendations for low EMI operation
and maximum thermal performance are available in the
data sheet section Low EMI PCB Layout.
The Efficiency vs Load graph shows the efficiency and
the power loss of the circuit with a 3.3V input in Burst
Mode operation.
Design files for this circuit board are available
Specifications are at T
A
= 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Voltage Range
2.25
5.5
V
V
OUT
V
OUT
Voltage Range*
1.774
1.8
1.826
V
I
OUT
OUTPUT Current
4
A
f
SW
Switching Frequency
3
6.6
10
MHz
t
ON
Top Switch Minimum On Time
22
ns
Duty Cycle
Top Switch Duty Cycle
100
%
*With 1% resistors. Accuracy will improve to within 1% using 0.1% FB resistors.
