1
DEMO MANUAL DC2543B
Rev. 0
DESCRIPTION
LTC7820EUFD
High Efficiency, Charge Pump
DC/DC Converter
Demonstration circuit 2543B is a high efficiency, high
density, open loop charge pump (inductorless) DC/DC
converter. This demo board is a voltage divider which
achieves a 2:1 step-down ratio from an input voltage from
36V to 60V. The output voltage is a fixed ratio of half of the
input voltage (V
IN
/2) and can supply a 10A load current.
This demo board has the option to deliver a 20A maximum
load with the addition of 15 chip capacitors. See Figure 8
and Figure 10 for the details.
The DC2543B provides a very high efficiency solution of
98.7% when converting 48V
IN
to 24V
OUT
at 10A as shown
in Figure 3. When configured for a 20A output, an effi-
ciency of up to 98.4% is achievable for a 48V
IN
to 24V
OUT
at 20A as shown in Figure 8.
The demo board features the
LTC
®
7820
, a fixed ratio high
voltage high power switched capacitor/charge pump
controller in a 4mm × 5mm QFN package. Please see
LTC7820 data sheet for more detailed information.
PERFORMANCE SUMMARY
The DC2543B needs to be powered on with no load cur-
rent or a very small load current (less than 50mA) with
the default setup. Large load current can be applied after
V
O
is established. The board offers a disconnect FET
option which is controlled by the LTC7820 FAULT pin
to disconnect the load during startup as shown in the
schematic. Please refer to “Voltage Divider Prebalance
Before Switching” section in the LTC7820 data sheet for
more details regarding the startup of the voltage divider.
The board also features some protection functions
such as overcurrent and thermal shutdown to make it a
reliable solution.
Design files for this circuit board are available.
Specifications are at T
A
= 25°C
PARAMETER
CONDITION
VALUE
Input Voltage Range
36V to 60V
Output Voltage, V
OUT
V
IN
= 36 to 60V, I
OUT
= 0A to 10A
V
IN
/2
Maximum Output Current, I
OUT
V
IN
= 36 to 60V, V
OUT
= V
IN
/2
10A
Typical Efficiency
V
IN
= 48V, V
OUT
= 24V, I
OUT
= 10A
98.7%
Peak Efficiency
V
IN
= 48V, V
OUT
= 24V
99%
Switching Frequency
200kHz
All registered trademarks and trademarks are the property of their respective owners.
NOTE:
DC2543B demo board includes a Schottky diode added across the output. This manual describes the demo
board entitled “Demo Circuit 2543B.” The DC2543B replaces the DC2543A.
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