Quick Start Guide for Linear Technology Demonstration Circuit 1019A

Quick guide from the manual

The Demonstration Circuit 1019A is a Dual White LED Driver Converter featuring the LT3497. It is designed to drive two independent LED strings at 20mA from a 3V-10V input. Before operating, ensure the input voltage does not exceed 10V. The board includes jumpers (JP1, JP2) that must be configured for testing.

Description

The 1019A demo circuit demonstrates the small size and low component count of the LT3497 in a 3mm x 2mm DFN package. It features internal Schottky diodes, high switching frequency, and internal open circuit protection. The board allows for various dimming controls, including optional N-MOSFET placeholders for direct PWM dimming.

Performance specifications

The following performance parameters are measured at TA = 25°C:

• Input Supply Range (VIN): 3V to 10V
• Output Current (IOUT): 20mA (19mA min, 21mA max)
• Output Voltage (VOUT): 19.5V
• Efficiency: 72.3% (at VIN=3.6V)
• Switching Frequency (Fs): 2.3 MHz (1.8 MHz min, 2.8 MHz max)
• Quiescent Current (IQ): 15mA (at VIN=4.2V, CTRL=ON, LEDs open)
• Quiescent Current in Shutdown (IQSHDN): 10µA (at VIN=4.2V, CTRL=OFF)

Quick start procedure

1. Place jumpers JP1 and JP2 in the ON position to test the circuit.
2. With the power off, connect the input power supply to the VIN and GND terminals.
3. Turn on the power at the input. Ensure the input voltage does not exceed 10V.
4. Check for proper voltages and currents. If LEDs do not light up, verify jumper settings.
5. Once operations are established, adjust the input within the operating range to observe parameters.

Measurement setup

When measuring input or output voltage ripple, avoid using a long ground lead on the oscilloscope probe. Measure the ripple by touching the probe tip directly across the VIN or VOUT and GND terminals.

Dimming control

To test filtered PWM dimming or direct DC dimming, remove jumper JP1 or JP2. Apply the PWM or DC signal to the SHDN/DIMMING CTRL1 or SHDN/DIMMING CTRL2 terminals and observe the LED output brightness. For direct PWM dimming, refer to the specific section in the LT3497 datasheet.

Safety warnings

WARNING: Do not look directly at the operating LED. This circuit produces light that can damage eyes.

Schematic

The demonstration circuit includes design files and a schematic layout for the LT3497EDDB, which can be referenced for modifying the circuit or understanding the component connections.