DC1260A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1260A-A/1260A-B
2A SYNCHRONOUS STEP-UP DC/DC CONVERTER
LTC3539/3539-2
DESCRIPTION
Demonstration circuits 1260A-A and 1260A-B are high
efficiency synchronous boost converters capable of
operating with an input voltage range from 0.7V to
5.5V. The 2X3 mm DFN thermally enhanced package
with a 1MHZ switching frequency (2MHz for the -2
part) and the 2A internal switches provide a very tiny
overall solution. The LTC3539/LTC3539-2 also feature
output disconnect, selectable PWM or BURST mode
operation, Shutdown capability and the input voltage
can be greater or less than the output voltage.
This demonstration circuit allows the user to quickly
evaluate the LTC3528 performance. Jumpers are provided for selecting several regulated output voltages,
and jumpers for low quiescent current shutdown and
PWM/BURST mode. Terminals on the board allow
easy hookup to an input supply and output load.
When Burst mode is selected, the converters automatically enter low quiescent current Burst-Mode operation at low current levels, and return to fixed frequency PWM operation at higher current levels. In
PWM mode, the converter operates continuously in
fixed frequency.
Design files for this circuit board are available. Call the
LTC factory.
LTC and Burst Mode are trademarks of Linear Technology Corporation
Table 1. Typical Specifications (25°C)
VIN, Input Start-up Voltage
VIN, Input Voltage Range (after start-up)
1.8V VOUT
3.3V VOUT
5V VOUT
Output Ripple Voltage (burst mode)
Output Ripple Voltage (fixed frequency)
Efficiency
650mV
0.5V to 5V
1.8V ± 2.5%
3.3V ± 2.5%
5.0V ± 2.5%
8mV p-p
15mV p-p
90%
VIN = 1V, IOUT = 100mA
VIN = 1.5V, IOUT = 200mA
VIN = 1.5V, IOUT = 200mA
VIN = 1.5V, VOUT = 3.3V IOUT = 3mA
VIN = 1.5V, VOUT = 3.3V IOUT = 300mA
VIN = 1.8V, VOUT = 3.3V IOUT = 100mA
Resistive
Load
Input
Power
Supply
V
+
0 to [email protected]
V
A
A
Figure 1. Demonstration Circuit Test Setup
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1260A-A/1260A-B
2A SYNCHRONOUS STEP-UP DC/DC CONVERTER
Demo #
1260A-A
1260A-B
Part #
LTC3539EDCB
LTC3539EDCB-2
Part Marking
Frequency
LDCS
LDPH
1 MHz
2 MHz
Table 1. Demonstration Circuit Board Information
QUICK START PROCEDURE
There is one demonstration circuit board for both
LTC3539 versions. The boards are identified 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 the voltage select jumpers. (With
no jumper installed, the output voltage is 5V.) With
jumper JP2 in the ON position and JP1 in BURST,
connect voltmeters and ammeters as shown on the
test setup. Connect a power supply to the +VIN 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 voltage. At approximately 650mV, 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 feature 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.
Refer to the data sheet curves for typical output current for various input/output voltages.
The input voltage can exceed the output voltage and
still maintain regulation, although the load current is
less and efficiency is lower. It should be noted that
the output voltage ripple will increase as Vin approaches Vout. The increase will occur in a narrow
range when Vin is between 100 and 300mV below
Vout. The ripple voltage in this range can be from
30mV to 100mV pp.
When evaluating the circuit at very low input voltages, it is important to monitor the input voltage directly at the input terminals of the circuit board. At
these low input voltages, any voltage drop in the
power supply wire, connections and Ammeter will
result in the input voltage at the input terminals
dropping below the minimum 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. Additional pads directly above the output capacitor (C4) are provided if
additional output capacitance is needed.
When verifying output ripple, it is important to use
the scope probe connection as shown in figure 3.
Typical output voltage ripple with a 1k and 100-Ohm
load are shown in figure 2. The 1k load shows Burst
mode ripple, while the 100 Ohm load is fixed frequency PWM mode.
See LTC3539/3539-2 Data Sheet for additional information
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1260A-A/1260A-B
2A SYNCHRONOUS STEP-UP DC/DC CONVERTER
1k Load
50µs/div
20mV/div Output Ripple
10ž Load
Vin = 1.2V
200ns/div
Vout = 3.3V
Figure 2. Typical Output Ripple Voltage (upper – Burst, lower – fixed frequency PWM)
VOUT
GND
Figure 3. Scope Probe Placement for Measuring Output Ripple Voltage
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1260A-A/1260A-B
2A SYNCHRONOUS STEP-UP DC/DC CONVERTER
4
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