QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 627
DESCRIPTION
BOOST CONVERTER
LT3461 / LT3461A
Demonstration circuit 627 features the LT3461 /
LT3461A in a 12.0V output boost converter which
operates from an input voltage of 3V to 6V. The
maximum output current is 70mA when powered
from a 5.0V input and 40mA when powered from a
3.3V input. A soft-start option is provided by the
SHDN pin and can be configured with an on-board RC
filter.
The DC627A comes in two versions. The “-A” version
uses the LT3461 and the “-B” version uses the
LT3461A.
Design files for this circuit board are available. Call
the LTC factory.
LT is a trademark of Linear Technology Corporation
The internal schottky of the LT3461 / LT3461A reduces part count and the high switching frequency
allows the use of a small SMT inductor and output
capacitors. The small size of the circuit makes it ideal
for space-sensitive applications.
Table 1. Performance Summary (TA = 25°C)
PARAMETER CONDITION DC627A-A
VALUE
LT Part LT3461ES6 LT3461AES6
Minimum Input Voltage 3V 3V
Maximum Input Voltage 6V 6V
DC627A-B
VALUE
Output Voltage V
Maximum Output Current
Typical Efficiency
Typical Output Voltage Ripple
(20MHz BW)
Nominal Switching Frequency 1.3MHz 3.0MHz
V
OUT
= 3V to 6V 12V ±4% 12V ±4%
IN
V
= 3.3V
IN
= 5.0V
V
IN
V
= 3.3V, I
IN
V
IN
V
IN
V
IN
= 5.0V, I
= 3.3V, I
= 5.0V, I
OUT
OUT
OUT
OUT
= 40mA
= 70mA
= 40mA
= 70mA
40mA
70mA
79%
83%
20mV
28mV
P–P
P–P
40mA
70mA
76%
81%
9mV
P–P
12mV
P–P
QUICK START PROCEDURE
Demonstration circuit 627 is easy to set up to evaluate the performance of the LT3461 or LT3461A. Refer
to Figure 1 for the proper measurement equipment
setup and follow the procedure below:
1.
Place jumper JP1 in the “ON” position if not already done.
2.
With power off, connect the input power supply.
3.
Turn on the input power source and set it to 3.3V.
The output should be 12.0V ±4% at no load.
4.
Connect the load from VOUT to GND and set to
40mA. The output should still be 12.0V ±4%.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 627
5.
Increase the input voltage to 5.0V and apply 70mA
load and re-check regulation.
6.
Measure the DC input current at V
I
= 70mA.
OUT
a.
For the DC627A-A, the input current should be
less than 215mA.
b.
For the DC627A-B, the input current should be
less than 225mA.
7.
Monitor the output voltage ripple. Refer to Figure 2
for the proper measurement technique.
8.
Measure the output ripple frequency.
= 5.0V and
IN
BOOST CONVERTER
a.
For the DC627A-A, the frequency should be between 1.0MHz and 1.7MHz.
b.
For the DC627A-B, the frequency should be between 2.1MHz and 3.9MHz.
NOTE:
If this circuit will be used in a hot plug application, then be sure to measure the inrush current. The
maximum non-repetitive surge current the internal
schottky can handle is 1.5A. The inrush current can
be monitored by measuring the current through the
inductor when VIN is initially applied. Refer to the data
sheet for more details.
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
2
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