DC1566A - Demo Manual

DEMO CIRCUIT 1566
LT3970
QUICK START
GUIDE
LT3970
40V, 350mA Step-Down Regulator with 2.5µA
Quiescent Current and Integrated Diodes
DESCRIPTION
Demonstration circuit 1566 is a monolithic stepdown DC/DC switching regulator featuring the
LT3970. The switching frequency is adjustable
up to 2MHz. The demo circuit is designed for
5V, 350mA output from a 6V to 40V input. The
wide input range of the LT3970 allows a variety
of input sources including automotive batteries
and 24V industrial supplies. Low ripple Burst
Mode increases the efficiency at the light load
while keeping the output ripple below 15mV.
The part is in shutdown when the EN pin is low
and active when the pin is high. The threshold
of the EN pin is accurate at 1V when Vin is
above 4.2V. Adding a resistor divider from Vin to
EN can program the LT3970 to regulate the
output only when Vin is above a desired voltage.
Performance Summary (TA = 25oC)
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Output Voltage VOUT
Typical switching Frequency
Maximum Output Current
Typical efficiency
Typical output voltage Ripple
The catch diode and boost diode are integrated
to reduce the components count and solution
size. The circuit consumes only 2µA of quiescent
current. The current mode control scheme creates fast transient response and good loop stability. The catch diode current is limited to protect the part under short circuit and overvoltage
conditions.
The LT3970 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 1566.
Design files for this circuit board are available. Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
CONDITION
VIN=12V, Iout=350mA
VIN=12V, Iout=350mA
VALUE
6V
40V
5.04V ±3%
600kHz
350mA
84.5%
10mV
QUICK START PROCEDURE
Demonstration circuit 1566 is easy to set up to
evaluate the performance of the LT3970. 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
LT3970
1.
2.
3.
Place JP1 on the ON position.
With power off, connect the input
power supply to Vin and GND.
Turn on the power at the input.
5.
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.
NOTE. Make sure that the input voltage does not exceed
40V.
4.
Check for the proper output voltage.
NOTE. If there is no output, temporarily disconnect the load
to make sure that the load is not set too high.
Figure 1. Proper Measurement Equipment Setup
2
LT3970
GND
VIN
Figure 2. Measuring Input or Output Ripple
3
LT3970
4
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