1
dc1881af
DEMO MANUAL DC1881A
DESCRIPTION
LTC3789EUFD
High Efficiency Compact
Buck-Boost Converter
Demonstration circuit 1881A is a high efficiency syn-
chronous buck-boost DC/DC converter with 6V to 36V
input range. It can supply 2.5A maximum load current at
12V output. The demo board features the LTC
®
3789EUFD
controller. The constant-frequency current mode architec-
ture 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 trans-
fers between operation modes, the LTC3789 is ideal for
automotive, telecom, distributed DC power systems and
battery-powered applications. This board has a compact
solution size with dual SO-8 MOSFETs, small inductor and
capacitor footprints. The package of LTC3789EUFD is a
small, low thermal impedance 4mm
×
5mm 28-Lead QFN.
L
, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
The light load operation mode of the converter is determined
with the MODE/PLLIN pin. Use the JP2 jumper to select
pulse skipping mode or forced continuous mode (CCM)
operation. Switching frequency is preset at about 400kHz.
The converter can also be externally synchronized through
the MODE/PLLIN pin (PLLIN terminal on the board). To
shut down the converter, one simple way is to 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
Specifications are at T
A
= 25°C
PARAMETER
CONDITION
VALUE
Input Voltage Range
6V to 36V
Output Voltage, V
OUT
V
IN
= 6V to 36V, I
OUT
= 0A to 2.5A
12V ±2%
Maximum Output Current, I
OUT
V
IN
= 6V to 36V, V
OUT
= 12V
2.5A
Typical Output Ripple
V
IN
= 36V, I
OUT
= 12A (20MHz BW)
44mV
P-P
Typical Efficiency
V
IN
= 12V, V
OUT
= 12V, I
OUT
= 2.5A
97.2%
Typical Switching Frequency
400kHz