Demo Board DC409 Quick Start Guide
The LTC3402 is a high efficiency, step-up DC/DC converter that starts up from an input
voltage as low as 1V. Once it starts up, the LTC3402 is supplied from the output voltage
and the input voltage can go well below 1V. The device includes a 0.16Ω N-channel
MOSFET and a 0.18Ω P-channel synchronous rectifier, which give higher than 90%
efficiency in many applications. Switching frequencies are programmed with an external
resistor and can also be synchronized to an external clock.
Demonstration Circuit DC409 demonstrates a 600kHz converter that achieves a useful
balance of efficiency and size. The output voltage of this circuit is jumper selectable
between 3.3V and 5V. (This demo board ships with the output set to 5V. To change the
output to 3.3V, remove jumper JP2.)
Performance Summary
Available power for this circuit depends on input and output voltages. The following
table shows Maximum load current for several input-output conditions.
Parameter
Maximum Load Current
Condition
V
OUT
= 3.3V, V
IN
= 2.0V
V
OUT
= 5.0V, V
IN
= 2.0V
V
OUT
= 5.0V, V
IN
= 2.7V
Value
850mA
550mA
800mA
Quick start guide
Refer to Figure 1 for proper measurement equipment setup and Figure 2 for the proper
ripple measurement technique. Then, follow this procedure:
1.
Apply a voltage source to the input of the circuit between the V
IN
and GND terminals.
The circuit will start up with an input voltage higher than 1V. Do not apply more than
5V to the input. Note that the boost circuit will regulate the output only when the
input voltage is less than the desired output voltage.
Attach a voltmeter or oscilloscope probe between the V
OUT
and GND terminals of the
circuit to monitor the output.
Attach a load to the output.
The available output power depends on the input and output voltages. Please refer to
the performance summary above for maximum current at different inputs and outputs.
2.
3.
Page 1 of 1
4.
The MODE pin (jumper JP1) controls the operating modes of the LTC3402 circuit.
When open, it runs in Burst Mode. The peak inductor current rises to one third of the
2A current limit and returns to zero before the end of each cycle. When connected to
GND, it maintains low noise, constant frequency operation. This pin can also be used
to synchronize to an external clock, which also disables Burst Mode.
To shutdown the LTC3402, short SHDN to GND on jumper JP1.
DC409
LTC3402EMS
SYNCHRONOUS BOOST CONVERTER
LINEAR TECHNOLOGY
(408) 432-1900
www.linear-tech.com
JP1
GND
SHDN
PGOOD
MODE
GND
–
+
+
+
–
VIN
1V–4.5V
GND
–
JP2
VOUT
3.3V/5V
+
GND
+
–
+
–
–
LOAD
Figure 1.
Proper Measurement Equipment Setup
Vout
GND
Figure 2.
Scope Probe Placement for Measuring Output Ripple
Page 2 of 2
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