Linear Technology LTC3440 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 425B

DESCRIPTION

Demonstration Circuit 425B is a constant-frequency
synchronous Buck-Boost
LTC3440. The input range is from 2.5V to 5.5V, mak-
ing it ideal for single-cell lithium-ion or three-cell
NiCd/NiMH battery applications. This converter pro-
vides up to 95% efficiency, much higher than tradi-
tional Buck-Boost converters. For 2.5V minimum in-
put voltage, this converter can provide up to 500mA
load current.
The output voltage is set at 3.3V. A different output
voltage in the range of 2.5V to 5.5V can be obtained
by changing one of the feedback resistors. The fre-
QUICK START GUIDE
Refer to Figure 1 for the connection diagram and fol-
low the procedure below:
Apply a voltage source to the input of the circuit
1.
between the V and GND terminals. The circuit will
IN
start up at input voltage higher than 2.5V.
Do not apply more than 5.5V to the input.
NOTE
converter using the
Figure 1. Proper Measurement Equipment Setup
1MHZ SYNCHRONOUS BUCK-BOOST
quency is set at 1MHz, which is a good trade-off be-
tween efficiency and size. The frequency can be modi-
fied by changing R6 or by synchronizing to an exter-
nal clock. In shutdown, the board draws about 2.5µA,
where 2µA goes through the 1MΩ pull up resistor
(R4) and the IC itself draws less than 1µA.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Attach a voltmeter or oscilloscope probe between
2.
the V and GND terminals of the circuit to monitor
OUT
the output. To start the circuit, the shunt at JP1
needs to be put in RUN position.
Attach a load to the output. The available output
3.
current depends on the input voltage.
LTC3440
1