Analog Devices DC2757A Demo Manual

DESCRIPTION
Demonstration circuit 2757A is a 6A buck-boost DC/
DC converter featuring the
I monolithic buck-boost converter with programmable
Q
soft-start.
The DC2757A demo board has four user-selectable oper-
ating modes:
• An accurate programmable EN/UVLO pin, which is
used to ENABLE the converter (JP1).
• BURST MODE and External CLK/Fixed Frequency
©
PWM (JP2).
• Programmable Soft-Start (JP3).
• Selectable (2.2MHz) and Adjustable Switching
Frequency RT (500kHz to 4MHz) (JP4).
The LT3154 uses average current mode control to sim-
plify voltage loop compensation and provide good line
and load transient response.
The DC2757A operates with a 1.8V to 5.5V input voltage
range. The demo board has been designed with the out-
put voltage set to 3.3V. The LT3154 incorporates a pro-
prietary low noise switching algorithm which optimizes
PERFORMANCE SUMMARY
PARAMETER
Input Voltage V Range
IN
Switching Frequency (f )
SW
Output Voltage V
OUT
Output Current I
OUT
Efficiency
Note: Demo board output current is a function of input voltage. Refer to the data sheet for more information.
LT 3154, a low noise, low-
®
Specifications are at T
CONDITIONS
Operating
RT (R4 = 34kΩ)
Internal
R5 = 1MΩ
R6 = 432kΩ
V > 3.3V
IN
DEMO MANUAL DC2757A
5.5V 6A Low-Noise Monolithic
Buck-Boost DC/DC Converter
efficiency with input voltages above, below, or equal to the
output voltage and ensures seamless transitions between
operating modes.
In PWM mode, the LT3154 can operate with a switch-
ing frequency between 500kHz to 4MHz by program-
ming the RT resistor R4. It also has a selectable switch-
ing frequency (2.2MHz) to optimize small size with high
efficiency operation. The LT3154 can be synchronized to
the External CLK provided RT is programmed 25%-50%
below the synchronization frequency.
The LT3154 has a Soft-Start feature and can be pro-
grammed with the soft-start capacitor C13 (EXT SS). It
also has a selectable internal soft-start (INT SS) of 2.2ms.
Figure 2 shows typical demo board efficiency. Figure 3
and Figure 4 show the load step response.
The LT3154 data sheet has detailed information about
the operation, specifications, and applications of the part.
The data sheet should be read in conjunction with this
Quick Start Guide.
Design files for this circuit board are
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= 25°C
A
LT3154
available.
MIN TYP MAX
1.8 5.5
3.2
2.2
3.3
5A
See Figure 2
UNITS
V
MHz
V
%
Rev. 0
1