AN2809

Getting started

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9

Getting started

The following step-by-step sequences are provided as a guideline to quickly evaluate the

performance of the LED7706 board.

9.1

Quick startup

Note:

Working in a ESD-protected environment is highly recommended. First check all wrist straps

and mat earth connections before handling the LED7706 board.

1.

Connect the power supply to the LED7706 board and insert the A-meter as shown in

Figure 8. Connect a V-meter between VBOOST and ground to monitor the output

voltage.

2.

Connect the proper WLEDs array to the J8 connector or to the row1-row6 and

VBOOST terminals of the LED7706 board.

3.

Set the PWM signal (20 kHz, 5% duty-cycle, 3.3 V CMOS logic levels) on a signal

generator and provide it to the DIM input.

4.

Set SW1 and SW2 to the lower position (fixed frequency and MODE to AVCC). Do not

change jumper settings when the board is switched on.

5.

Set the input voltage to 12 V.

6.

Turn on the PWM generator.

7.

Turn on the VIN supply: the device turns on.

8.

Vary the input voltage in the range 4.5–32 V.

9.

Set the input voltage to 12 V.

10. Vary the dimming duty-cycle from 1 to 100%.

11. Check the shape of the rows’ current at a 1% dimming duty-cycle.

Note:

When measuring the current of row x, an auto-ranging A-meter can trigger the open-row or

shorted-LED fault detection during the automatic scale selection procedure. Disabling the

auto-ranging option on the A-meter is recommended.