DC1248A - Demo Manual

DEMO CIRCUIT 1248
LT3509
QUICK START
GUIDE
LT3509
36V, 700mA Dual Monolithic Buck Regulator
DESCRIPTION
Demonstration circuit 1248 is a dual monolithic
buck regulator featuring the LT3509. The demo
circuit is designed for 5V and 3.3V output from a
6.5V to 36V input. The input voltage can go up
to 60V without damaging the part. The wide input range of the LT3509 allows a variety of input
sources including automotive batteries and 24V
industrial supplies. The switching frequency can
be set from 300kHz to 2.2MHz by a single external resistor, and it is synchronizable over the
full range. The power switches, the compensation components and the boost diodes are all
integrated into the silicon. The shutdown and
soft start function is independent for each channel. The current mode control scheme creates
Performance Summary (TA = 25oC)
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Output Voltage VOUT1
Output Voltage VOUT2
Maximum Output Current 1
Maximum Output Current 2
Switching Frequency
Efficiency
Voltage Ripple 1 pk-pk
Voltage Ripple 2 pk-pk
fast transient response and good loop stability.
The part has overvoltage lockout, cycle by cycle
current limit and thermal shutdown. DA pin can
further protect the silicon under fault conditions
by sensing the diode current.
The LT3509 datasheet gives a complete description of the part, operation and application
information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1248.
Design files for this circuit board are available. Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
CONDITION
VIN=24V, Iout1=700mA, Iout2=700mA
VIN=24V, Iout1=700mA, Vout1=5V
VIN=24V, Iout2=700mA, Vout2=3.3V
VALUE
6.5V
36V (60V transient)
4.98V ±4%
3.33V ±4%
700mA
700mA
700kHz
83.74%
20mV
18mV
QUICK START PROCEDURE
Demonstration circuit 1248 is easy to set up to
evaluate the performance of the LT3509. 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 the input power supply to Vin and GND.
2. Turn on the power at the input.
1
LT3509
NOTE. Make sure that the input voltage does not exceed
36V.
3. Check for the proper output voltages. If there
is no output, temporarily disconnect the load
to make sure that the load is not set too
high.
4. Once the proper output voltage is established, adjust the load within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
2
LT3509
3
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