QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 560
WCDMA CELLULAR PHONE BUCK REGULATOR
LTC3403EDD
DESCRIPTION
Demonstration circuit 560 is a constant-frequency step-
down converter, using the LTC3403 monolithic synchro-
nous buck regulator. It is specifically designed for
WCDMA power amplifier applications. The output volt-
age can be dynamically controlled from 0.3V to 3.5V. A
0.2Ω internal bypass P-channel MOSFET connects the
V
OUT
to V
IN
reducing the power loss through the buck
regulator. DC560 is capable of delivering up to 600mA of
output current for an input voltage range of 2.7V to 5V.
The efficiency of the DC560 is very high: up to 96%. In
Burst Mode
TM
operation, the DC supply current is typi-
cally only 20µA at no load, and less than 1µA in shut-
down.
The LTC3403 comes in a small 8-Pin DFN package and
has an operating frequency of 1.5MHz (allowing the ex-
clusive use of low profile surface mount components).
These and other features make demonstration circuit
560 ideal for single-cell Li-ion-powered hand-held appli-
cations.
Design files for this circuit board are available. Call
the LTC factory.
QUICK START PROCEDURE
Demonstration circuit 560 is easy to set up to evaluate
the performance of the LTC3403EDD. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
NOTE:
When measuring the input or output voltage rip-
5.
Turn on the V
REF
power supply.
NOTE:
Make sure that the input voltage V
REF
does not
exceed V
IN
.
6.
For VREF < 1.2V, check for the output voltages
ple, care must be taken to avoid a long ground lead on
the oscilloscope probe. Measure the input or output
voltage ripple by touching the probe tip directly across
the Vin or Vout and GND terminals. See Figure 2 for
proper scope probe technique.
1.
Place jumper JP2 in the FC position, JP1 in the ON
V
OUT
= 3 • V
REF
7.
For V
REF
> 1.2V, VOUT is directly connected to VIN.
V
OUT
= V
IN
.
If there is no output, temporarily disconnect the load
to make sure that the load is not set too high.
8.
Once the proper output voltages are established, ad-
position.
2.
With power off, connect the input power supply V
IN
to
VIN and GND.
3.
Connect input power supply V
REF
to REF and GND.
4.
Turn on the power at VIN.
NOTE:
Make sure that the input voltage at VIN does not
just the loads within 600mA range and observe the
output voltage regulation, ripple voltage, efficiency
and other parameters.
9.
To test Burst Mode
operation, set JP2 in the Burst
position and JP1 in the ON position, and repeat steps
2 to 7.
TM
exceed 5V.
1
Embedded System
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