4
DEMO MANUAL DC257
NO-DESIGN SWITCHER
QUICK START GUIDE
This demonstration board is easily set up to evaluate the
performance of the LTC1707 IC. Please follow the proce-
dure outlined below for proper operation.
• Refer to Figure 5 for proper connection of monitoring
equipment to ensure correct measurement.
• Connect the input power supply to the V
IN
and GND
terminals on the left-hand side of the board. Do not
increase V
IN
over 10V or the part will be damaged.
• Connect the load between the V
OUT
and GND
terminals on the right side of the board.
• The RUN/SS pin can be left unconnected. To shut
down the LTC1707, tie this pin to GND.
• Set the desired output voltage with jumper JP1, as
shown in Figure 2 and Table 1.
JP1 POSITION
OUTPUT VOLTAGE
“1.5V”
1.51V
“1.8V”
1.82V
“2.5V”
2.52V
“2.9V
2.94V
“3.3V”
3.33V
“OPEN”
Figure 2. Output Voltage Selection (JP1)
(3.3V Position Shown)
1.8V
1.5V
2.5V
2.9V
3.3V
OPEN
JP1
DC257 F02
Table 1. Output Voltage Selection
OPERATIO
U
The circuit in Figure 1 highlights the capabilities of the
LTC1707. The application circuit is set up for a variety of
output voltages. Output voltages from 1.5V to 3.3V or user
programmable voltages can be obtained by selecting the
appropriate jumper position.
The LTC1707 is a monolithic synchronous step-down
switching regulator using a fixed-frequency architecture.
Burst Mode operation provides high efficiency at low load
currents. Operating efficiencies typically exceed 90% over
two decades of load current range. 100% duty cycle
provides low dropout operation, which extends operating
time in battery-operated systems.
Do not use small spring-clip leads when testing this
circuit. Soldered wire connections are required to properly
verify the performance of the PC board.
This demonstration board is intended for the evaluation of
the LTC1707 switching regulator IC and was not designed
for any other purpose.
The operating frequency of this demo circuit is 350kHz,
the frequency of the LTC1707’s internal oscillator. For
higher frequencies, SYNC/MODE (E8) can be synchro-
nized with an external clock. Burst Mode operation is
automatically disabled when the SYNC/MODE pin is ex-
ternally driven. Grounding SYNC/MODE also disables
Burst Mode operation, potentially reducing noise and RF
interference.
Soft-start is provided by an external capacitor, C
SS
, which
can be used to properly sequence supplies. The maximum
operating current level is 0.6A.
This demo board is optimized for 3.3V outputs and 5V
input. Output voltages from 1.5V to 3.3V are available by
selecting the appropriate position of JP1. For other output
voltages, select the OPEN position and add an appropriate
resistor value in the space provided. The output voltage
must never exceed 3.3V because the output capacitor may
be damaged. The input supply can range from 2.85V to
8.5V.