DC958A - Demo Manual

LT3506A
AND LT3506
DEMO
CIRCUIT
958
LT3506A and LT3506
Dual Monolithic 1.6A StepDown Switching Regulator
DESCRIPTION
Demonstration circuit 958 is a Dual Monolithic 1.6A
Step-Down Switching Regulator featuring the
LT3506A and LT3506. The top half of the board
features the LT3506A circuit. The bottom half of
the board features the LT3506 circuit. These two
circuits are totally independent on the demo board.
The main difference between the two circuits is the
switching frequency. The switching frequency of
the LT3506A circuit is 1.1MHz. The LT3506 switching frequency is 575KHz. Higher switching frequency allows smaller components in a given application. Lower switching frequency gives higher
efficiency and allows a circuit to operate at a lower
duty cycle.
The LT3506A circuit takes a 6.8V to 25V input and
generates a 5V and a 3.3V output, both at 1.6A.
The LT3506 circuit takes a 3.6V to 21V input and
generates a 1.8V and a 1.2V output, both at 1.6A.
The wide input voltage of the LT3506A and the
LT3506, 3.6V to 25V, accepts a variety of power
PERFORMANCE SUMMARY
SYMBOL
VIN
VIN
VOUT1
VOUT2
VOUT3
VOUT4
IOUT
VRIPPLE
η
PARAMETER
Input Supply Range
Input Supply Range
Output Voltage Range
Output Voltage Range
Output Voltage Range
Output Voltage Range
Output Current
Switching Frequency
Switching Frequency
Output Ripple
Efficiency
η
Efficiency
F
F
sources, from lead-acid batteries and 5V rails to
unregulated wall adapters and distributed power
supplies. The output voltage of both the LT3506A
and LT3506 can be as low as 0.8V.
The LT3506 high switching frequency and current
mode control allow the use of small, low profile
surface mount components. The circuit is stable
with ceramic capacitors. The low ESR of a ceramic
capacitor and high switching frequency results in
very low, predictable output ripple.
The LT3506 datasheet gives complete description
of the part, operation and application information.
The datasheet must be read in conjunction with
this quick start guide for working on or modifying
the demo circuit 958.
Design files for this circuit board are available.
Call the LTC factory.
LT is registered trademark of Linear Technology
Specifications are at TA = 25°C
CONDITIONS
LT3506A Circuit (TOP)
LT3506 Circuit (BOTTOM)
LT3506A Circuit (TOP)
LT3506A Circuit (TOP)
LT3506 Circuit (BOTTOM)
LT3506 Circuit (BOTTOM)
Each Output
LT3506A Circuit (TOP), IOUT = 1.6A
LT3506 Circuit (BOTTOM), IOUT = 1.6A
Each Output, VIN = 12V, IOUT = 1.6A
LT3506A Circuit (TOP),
VIN = 6.8V, IOUT1 = 0.9A, IOUT2 = 0.9A
LT3506 Circuit (BOTTOM),
VIN = 3.6V, IOUT3 = 0.9A, IOUT4 = 0.9A
MIN
6.8
3.6
4.85
3.2
1.746
1.164
TYP
5
3.3
1.8
1.2
1100
575
15
86.5
78
MAX
25
21
5.15
3.4
1.854
1.236
1.6
UNITS
V
V
V
V
V
V
A
KHz
KHz
mV
%
%
1
LT3506A AND LT3506
QUICK START PROCEDURE
Demonstration circuit 958 is easy to set up to
evaluate the performance of the LT3506A and
LT3506. Refer to Figure 1 for proper measurement
equipment setup and follow the procedure below:
NOTE. When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscilloscope
probe. Measure the input or output voltage ripple by touching the
probe tip directly across the VIN or VOUT and GND terminals. See
Figure 2 for proper scope probe technique.
1. With power off, connect a 6.8V–25V or a 3.6V21V input power supply to the VIN and the GND
terminals on the board corresponding to the top
circuit or the bottom circuit. Each circuit is powered separately from its own VIN and GND.
2. Turn on the power at the input.
3. Check for the proper output voltages. VOUT1 =
5V, VOUT2 = 3.3V, VOUT3 = 1.8V, VOUT4 =
1.2V
NOTE. If there is no output, temporarily disconnect the load to
make sure that the load is not set too high.
4. The RUN/SS and the Power Good functions are
optional and their terminals can be left floating
(disconnected) if their functions are not being
used. Connecting a RUN/SS terminal to GND
will disable the corresponding output.
5. Once the proper output voltages are established, adjust the loads within the operating
range and observe the output voltage regulation,
ripple voltage, efficiency and other parameters.
NOTE. Make sure that the input voltage does not exceed 25V.
2
LT3506A AND LT3506
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
3
LT3506A AND LT3506
4
LT3506A AND LT3506
5
Similar pages