Linear LTC1704 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 357
550KHZ SYNCHRONOUS BUCK CONVERTER AND LINEAR REGULATOR
DESCRIPTION
Demonstration circuit 357 is a dual
power supply with one switcher and
one LDO regulator.
LTC1704 and LTC1704B.
version features burst mode operation
at light load. The B version does not
have burst mode. The input voltage is
5V nominal, the switcher output is
set at 1.8V by a feedback resistor
divider and the LDO output is set at
1.5V by its feedback
vider. The switcher uses Mosfet R
Table 1. PERFORMANCE SUMMARY
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
V
OUT1
V
OUT2
Typical V Output Ripple
OUT1
Nominal Switching Frequency
QUICK START PROCEDURE
Demonstration circuit 357 is easy to
set up to evaluate the performance of
the LTC1704. Refer to Figure 1 for
proper measurement equipment setup,
and follow the procedure below:
When measuring the input or out-
NOTE:
put voltage ripple,
taken to avoid a long ground lead on
the oscilloscope probe. Measure the
input or output
touching the
across the Vin or Vout and GND termi-
nals.
It features the
The LTC1704
resistor
CONDITION
V = 4.75V to 5.5V, I
IN
V = 1.8V, I
IN_LDO
V = 5V, I
IN
care must
voltage ripple
probe tip directly
for current limit. This improves ef-
ficiency
power loss of discrete sense resis-
tors. The LDO can use the switcher
output or an external supply as its
input. The output voltages can be re-
programmed within certain limits in
accordance
tions.
Design files for this circuit board
di-
are available. Call the LTC factory.
DS(ON)
= 0A to 15A
OUT1
= 0A to 1.5A
OUT2
= 15A
CORE
Place jumper JP1 in the ON posi-
1.
tion.
Place Jumper JP2 in VOUT1 position.
2.
With power off, connect the input
3.
power supply to Vin and GND, making
sure voltage
be
than 6V.
Turn on the power at the input. Set
4.
Vin=5V
by
Check for the proper output volt-
5.
ages. Vout1
Vout2 = 1.470V to 1.530V
LTC1704/LTC1704B
and eliminates
with LTC1704
VALUE
4.75V
5.5V
1.8V +2%
1.5V ±2%
15mV
P–P
550kHz
is not set
= 1.764V
cost and
specifica-
greater
to 1.836V,
1