Linear Technology DC1757A Demo Manual

DESCRIPTION
Demonstration circuit 1757A is a high efficiency syn-
chronous buck-boost DC/DC converter with a 6V to 36V
input voltage range. It can supply a 12A maximum load
current with a 12V output. The demo board features the
LTC ® 3789EGN controller. The constant frequency current
mode architecture allows a phase-lockable frequency of up
to 600kHz, while an optional output current feedback loop
provides support for applications such as battery charging.
With a wide input range, wide output range and seamless
transfers between operation modes, the LTC3789 is ideal
for automotive, telecom, distributed DC power systems
and battery-powered applications.
PERFORMANCE SUMMARY
PARAMETER
Input Voltage Range
Output Voltage, V
OUT
Maximum Output Current, I
Typical Output Ripple
Typical Efficiency
Typical Switching Frequency
QUICK START PROCEDURE
Demonstration circuit 1757A is easy to set up to evalu-
ate the performance of the LTC3789. Refer to Figure 1 for
the proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply to V
(6V to 36V) and GND (input return).
2. Connect the 12V output load between V
(Initial load: no load).
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CONDITIONS
V = 6V to 36V, I
IN
V = 6V to 36V, V
OUT IN
V = 36V, I
IN
V = 12V, V
IN
OUT
DEMO MANUAL DC1757A
12V/12A Buck-Boost Converter
The light load operation mode of the converter is de-
termined with the MODE/PLLIN pin. Use JP2 jumper to
select pulse-skipping mode or forced continuous mode
(CCM) operation. The switching frequency is pre-set
at about 200kHz. The converter can also be externally
synchronized to an external clock through the MODE/
PLLIN pin (PLLIN terminal on the board). To shut down
the converter, force the RUN pin below 1.2V (JP1: OFF).
The power good output (PGOOD terminal) is low when the
output voltage is outside of the ±10% regulation window.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
= 25°C)
A
= 0A to 12A
OUT
= 12V
OUT
= 12A (20MHz BW)
OUT
= 12V, I = 12A
OUT OUT
3. Connect the DVMs to the input and outputs.
4. Turn on the input power supply and check for the proper
output voltages. V
5. Once the proper output voltages are established, ad-
IN
just the loads within the operating range and observe
the output voltage regulation, ripple voltage and other
and GND parameters.
LTC3789EGN
High Efficiency
VALUE
6V to 36V
12V ±2%
12A
109mV
P–P
97.9%
200kHz
should be 12V ±2%.
OUT
dc1757af
1