AS3677 datasheet(50/68 Pages) AMSCO

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AS3677

Datasheet - D e ta i l e d D e s c r i p t i o n

8.6

LED Test

Figure 27. LED Function Testing

The AS3677 supports the verification of the functionality of all the connected LEDs (open and shorted LEDs and short

to VSS can be detected). This feature is especially useful in production test to verify the correct assembly of the LEDs,

all its connectors and cables. It can also be used in the field to verify if any of the LEDs is damaged. A damaged LED

can then be disabled (to avoid unnecessary currents).

The current sources, dcdc converter, charge pump and the internal ADC are used to verify correct operation of each

LED string.

8.6.1

Function Testing for single LEDs connected to the Charge Pump

For any current source connected to the charge pump (CURR30-33) where only one LED is connected between the

charge pump and the current sink (see Figure 27) use:

Table 85. Function Testing for LEDs connected to the Charge Pump

Step

Action

Example Code

Switch on the charge pump and set it into manual

1:2 mode (to avoid automatic mode switching

during measurements)

Reg 23h

≤ 14h (cp_mode = 1:2, manual)

Reg 00h

≤ 04h (cp_on = 1)

Switch on the current sink for the LED to be tested

e.g. for register CURR31set to 9mA use

Reg 0Dh

≤ 5Ah (rgb1_current = 9mA)

Reg 02h

≤ 01h (rgb1_mode = on)

Measure with the ADC the voltage on CPOUT

Reg 26h

≤ 95h (adc_select=CPOUT,start ADC)

Fetch the ADC result from Reg 27h and 28h

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