QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 767
SINGLE LI-ION BATTERY POWERED BUCK REGULATOR FOR PDA APPS
1
LTC3447
DESCRIPTION
Demonstration Circuit 767 is an I2C controlled high effi-
ciency synchronous current mode buck regulator featur-
ing the LTC3447. The circuit is ideally suited for single
Li-Ion battery powered applications such as PDAs and
other Handheld Devices. The I2C Power Rail, VCCD, can
be connected to the main Supply Voltage VCCC. Both
input voltage ranges are 2.5V
5.5V. The buck regula-
tor has a programmable output range of 0.7V to 2.00V
with a 1A switch. The initial start-up voltage is set to
1.35V by feedback resistors R4 and R5 (the maximum
start-up voltage (equal to VCCC) can be set by changing
the R4 and R5 values). Automatic Burst Mode at light
loads extends battery life in portable systems. The Burst
Mode feature can be disabled using the I2C command.
Design files for this circuit board are available. Call
the LTC factory.
LT is a trademark of Linear Technology Corporation
Table 1.
Performance Summary (T
A
= 25°C)
PARAMETER CONDITION VALUE
VCCC Input Voltage Range 2.5V
5.5V
VCCD Input Voltage Range 2.5V
5.5V
V
OUT
Buck Output Voltage 0.7V
2.0V
Maximum Output Current VCCC = 3V, V
OUT
= 1.3V 600mA
Switching Frequency 1.0MHz Const.
QUICK START PROCEDURE
DC767 is easy to set up to evaluate the performance of
the LTC3447. Refer to Figure 1 for proper measurement
equipment setup and follow the procedure below:
1.
Connect a 100mA load, LOAD1, between the VOUT
and GND terminals on the right hand side of the
board.
2.
Apply 3.3V between the VCCC and GND terminals on
the left hand side of the board.
3.
Apply 3.3V between the VCCD and GND terminals on
the left hand side of the board.
4.
Connect the DC410 to the Computer’s serial port via a
9-pin RS232 cable.
5.
Connect 8V – 10V to the VinExt and Gnd terminals on
the DC410 (ensure the JP2 jumper on the DC410 is in
the VinExt position and the JP1\JP3 jumpers are in
their RES positions).
6.
Connect the DC767 to the DC410 via their 5 pin con-
nectors.
7.
Run the LVDC767.exe User Interface program pro-
vided to issue the I2C command with the relevant in-
formation (note: the serpdrv file must be stored in the
same directory as the LVDC767.exe file).
8.
To change the Buck voltage ... set the Buck Voltage
slider to whatever voltage you want the output to be
and click on the Buck Voltage slider's Write button.
