LINEAR TECHNOLOGY LT3686EDD Demo Circuit 1295A High Desinity Low Noise Power Mod User Guide
- June 5, 2024
- LINEAR TECHNOLOGY
Table of Contents
LT3686
DEMO CIRCUIT 1323
QUICK START GUIDE
LT3686EDD
37V, 1.2A, Buck Regulator
DESCRIPTION
Demo circuit 1323 is a current-mode PWM step-down DC/DC regulator with an
internal 1.2A power switch featuring the LT3686. The demo circuit is designed
for 3.3V output from a 5V to 37V input. The wide input range of the LT3686
allows a variety of input sources. The typical sources are automotive
batteries and industrial supplies. Its high maximum frequency allows the use
of tiny inductors and capacitors. Operating frequency above the AM band avoids
interfering with radio reception, making the LT3686 particularly suitable for
automotive applications.
Cycle by cycle current limit and DA current sense provide the protection
against shorted outputs. Soft-start and frequency foldback eliminate input
current surge during startup. An optional internal regulated active load at
the output via the BD pin keeps the LT3686 at full switching frequency at
light loads, resulting in low, predictable output ripple above the audio and
AM bands. Internal compensation and an internal boost diode reduce external
component count.
The LT3686 data sheet gives a complete description of the part, operation, and
application information. The data sheet must be read in conjunction with this
quick start guide for Demo Circuit 1323.
LT3686 is available in a 3mmx3mm DFN package.
Design files for this circuit board are available. Call the LTC factory.
LTC, LTM, LT and module are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
Performance Summary ( TA= 25°C )
| PARAMETER | CONDITION | VALUE |
|---|---|---|
| Minimum Input Voltage | 5V | |
| Maximum Input Voltage | 37V | |
| Output Voltage VouT | 3.3V ±3% | |
| Switching Frequency | 1 MHz | |
| Maximum Output Current | VIN=5-37V | 1.2A |
| Efficiency | VIN=12V, louT=1.0A | 81.% |
| Voltage Ripple | VIN=12V, louT=1.0A | 20mV |
QUICK START PROCEDURE
Demonstration circuit 1323 is easy to set up to evaluate the performance of
the LT3686. 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 the proper scope probe technique.
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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.
NOTE. Make sure that the input voltage does not exceed 55V. -
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. -
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.
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