Analog Devices Linear 2815A Demo Manual

26V, 9A Synchronous Buck-Boost DC/DC Converter
with Accurate Programmable Output Current Limit
DESCRIPTION
Demonstration circuit 2815A features the
wide operating range synchronous monolithic buck-boost
converter with programmable output current limit.
The DC2815A demo board has four user selectable oper-
ating modes:
• An accurate programmable EN/UVLO pin which is used
to ENABLE the converter (JP1).
• Programmable MPPC (Maximum Power Point Control)
for Input Regulation Set Point (JP2).
• Burst Mode operation and External CLK/Fixed
®
Frequency PWM (JP3).
• Programmable Output Average Current Limit Set Point
(JP4).
The LT3120 uses average current mode control to sim-
plify voltage loop compensation and provide good line
and load transient response.
The DC2815A operates with a 2.5V to 26V input voltage
range. The demo board has been designed with the output
voltage set to 5V. The LT3120 incorporates a proprietary
low noise switching algorithm which optimizes efficiency
with input voltages above, below or equal to the output
voltage and ensures seamless transitions between operat-
ing modes.
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. Please refer to the data sheet for more information.
DEMO MANUAL DC2815A
LT 3120, as In PWM mode, the switching frequency can operate
®
between 400kHz to 2MHz by programming the R
tor R5. LT3120 can be synchronized to an External CLK
provided R
chronization frequency.
The LT3120 has an optional programmable current limit
that can be used to control the output current. The current
limit circuit requires an external sense resistor connected
between ISP and ISN and the current limit value can be set
by adjusting R6 and C26 connected to PROG pin.
LT3120 also has programmable MPPC feature to set the
input regulation voltage and can be adjusted by changing
R13, R14 and C28.
Figure 2 shows typical demo board efficiency. Figure 3
and Figure 4 shows the load step response.
The LT3120 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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Specifications are at T
CONDITION
Operating
R5 = 75k
R2 = 1M, R3 = 187k
V > 5V
IN
is programmed 25% to 50% below the syn-
T
= 25°C
A
MIN
2.5
See Figure 2
LT3120
resis-
T
available.
TYP MAX UNIT
26 V
1 MHz
5 V
6.5 A
%
Rev. 0
1