QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1211A-A/1211A-B
1A SYNCHRONOUS BOOST DC/DC CONVERTER
2
Table 2. Demonstration Circuit Board Information
Board Number LTC Part Number Part Marking Mode
1211A-A LTC3528EDDB LCYD Auto Burst
1211A-B LTC3528BEDDB LDDG PWM
QUICK START PROCEDURE
There is one demonstration circuit board for
both LTC3528 versions. The boards are iden-
tified by the handwritten information on the top
of the pc board.
The boost converter can be evaluated using
the setup shown in Figure 1. Select one of the
three output voltages using jumpers JP1
through JP3. (With no jumpers installed, the
output voltage is 5V.) Set jumper JP4 in the
ON position and connect voltmeters and am-
meters as shown on the test setup. Connect a
power supply to the V
IN
and GND terminals
and a suitable load resistor between VOUT
and GND.
With a light load (1k resistor) at the output,
begin increasing the input power supply volt-
age. At approximately 700mV, the output will
rise to the selected regulated voltage. When
the output voltage exceeds the input voltage
by at least 240mV, the converter powers itself
from the output instead of the input. This fea-
ture allows the input voltage to drop as low as
500mV (at light loads) and still maintain a
regulated output voltage.
Increase the input voltage to approximately
1.5V and increase the load current. The
maximum load current depends on the input
and output voltage settings.
The input voltage can exceed the output volt-
age and still maintain regulation, although the
load current is less and efficiency is lower.
When evaluating the circuit at low input volt-
ages, it is important to monitor the input volt-
age directly at the input terminals of the circuit
board. At very low input voltages, voltage
drops in the power supply wire, connections
and Ammeter will result in the input voltage at
the input terminals dropping below the mini-
mum voltage required for operation.
Additional pc board pads are provided for an
optional input bypass capacitor (C1). It maybe
necessary when using long wires between the
power supply and circuit board, or for adding
a tantalum capacitor to minimize input voltage
transients that may occur when the input is
hot-switched. Also, pads on the board back-
side are provided for adding a small Schottky
diode (D1), which can increase the efficiency
slightly under some conditions. But adding a
diode defeats the output disconnect and short
circuit protection features.
When verifying output ripple, it is important to
use the scope probe connection as shown in
figure 2.
In Burst mode with light load current, the out-
put ripple voltage is higher than in non-burst
mode.
The PGOOD terminal is high when the output
voltage is in regulation and pulls low when the
output drops by approximately 10%.
See LTC3528 Data Sheet for additional information
V
OUT
GND
Figure 2. Scope Probe Placement for
Measuring Output Ripple Voltage
