QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 613
3A, 500KHZ, STEP-DOWN CONVERTER WITH 100UA QUIESCENT CURRENT
1
LT3435IFE
DESCRIPTION
Demonstration circuit 613 is a 3A, 500kHz, step-
down converter with 100uA quiescent current featur-
ing the LT3435IFE. It produces 5V at 2A from an in-
put range of 6.75V to 28V continuous, and can sur-
vive input transients up to 60V. The demonstration
circuit includes a shutdown control, synchronization
from 500kHz to 700kHz and a programmable power
good indicator.
The LT3435 is a 500kHz monolithic buck switching
regulator that accepts input voltages up to 60V. A
high efficiency 3A, 0.1Ω switch is included on the die
along with all the necessary oscillator, control and
logic circuitry. Current mode topology is used for
fast transient response and good loop stability.
Innovative design techniques along with a new high
voltage process achieve high efficiency over a wide
input range. Efficiency is maintained over a wide
output current range by employing Burst Mode
®
op-
eration at low currents, utilizing the output to bias the
internal circuitry, and by using a supply boost capaci-
tor to fully saturate the power switch.
For further information about the LT3435, please refer
to the LT3435 data sheet.
Design files for this circuit board are available. Call
the LTC factory.
, LTC , LT and Burst Mode are registered trademarks of Linear Technology
Corporation.
Table 1.
Performance Summary (TA = 25°C)
PARAMETER CONDITION VALUE
Minimum Turn On Input Voltage V
OUT
= 5VDC, I
LOAD
= 2A 6.75VDC
Minimum Turn Off Input Voltage V
OUT
= 5VDC, I
LOAD
= 2A 6.5V, typical
Maximum Input Voltage Continuous
100mS transient
28VDC
60VDC
Output Voltage V
OUT
V
IN
= 6.75 to 28VDC, I
LOAD
= 0 to 2A 5V + 4%
Maximum Output Current V
IN
= 6.75 to 28VDC, V
OUT
= 5VDC 2A
Nominal Switching Frequency 500kHz
Synchronization Frequency Range V
IN
= 6.75 to 28VDC, V
OUT
= 5VDC 500 – 700 KHz
QUICK START PROCEDURE
Demonstration circuit 613 is easy to set up to evalu-
ate the performance of the LT3435IFE. 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 out-
put 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.
While disconnected from the demonstration circuit,
set the output of the input power source to its
minimum positive value.
2.
With power off, connect the input power supply to
VIN and GND.
3.
Connect the load.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 613
3A, 500KHZ, STEP-DOWN CONVERTER WITH 100UA QUIESCENT CURRENT
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4.
Turn on the power at the input, ensuring that the
voltage applied to the demonstration circuit is less
than 28VDC.
5.
Check for the proper output voltages. The output
VOUT should be 5VDC.
NOTE:
If there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
6.
Once the proper output voltages are established,
adjust the loads within the operating range and ob-
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
7.
Verify the shutdown by pulling the SHDN (TP4)
terminal to a logic low level.
8.
Verify the power good function by monitoring the
timing and voltage levels of the output voltage and
PGOOD terminal (TP7).
9.
Verify the synchronization function by applying a
square wave signal of the appropriate amplitude
and frequency to the SYNC terminal (TP5).
Figure 1.
Proper Measurement Equipment Setup
VIN
GND
Figure 2.
Measuring Input or Output Ripple
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 613
3A, 500KHZ, STEP-DOWN CONVERTER WITH 100UA QUIESCENT CURRENT
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