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AS3668

Data Sheet - Detailed Description

8.10 LED Pattern Configuration

8.10.1 Single Pulse Mode

The AS3668 supports basically three basic LED pattern modes to create fancy lighting effect for the LEDs which can be connected to the current

sources CURR1, CURR2, CURR3 and CURR4. The first and basic mode is the “Single Pulse Mode”. This mode is basically defined out of five

parameters shown in Figure 42 below.

Figure 42. LED Pattern - Single Pulse Mode

The first parameter which can be configured in register pwm_dim_speed_up is tr_CURR. This time defines how long it takes to ramp up the

current to the defined value in registers curr1_current, curr2_current, curr3_current and curr4_current for each current source. The dimming of

the current source is of course logarithmic for a better visual effect but can be reconfigured to linear mode in register pwm_dim_shape. The

second parameter tf_CURR, which can be controlled in register pwm_dim_speed_down, defines the fall time for dimming down the LEDs. The

third parameter is ton_CURR and can be configured in register pattern_ton. It defines how long a current source keeps switched on with the

current configured in register curr1_current, curr2_current, curr3_current and curr4_current for each current source. Also this down dimming is

done with a logarithmic scale for a better visual effect. The last parameter toff_CURR defines how long the current sources or LEDs are switched

off until the whole pattern cycle starts from the beginning and can be configured in register pattern_toff.

Please mind that the settings for tf_CURR, tr_CURR, ton_CURR and toff_CURR are valid for all four current sinks at the same time. It is not

possible to define individual time values for each current source differently to each other. The only parameter which can differ from on current

source to another is the current which can be configured in registers curr1_current, curr2_current, curr3_current and curr4_current for each

current source individually. An example how the mode looks like for all four current sources in parallel can be seen in Figure 43. All current

sources work synchronously to each other with a fixed and parallel start point.

Table 32. Singe Pulse Mode Parameters

Symbol

Parameter

Condition

Min

Typ

Max

Unit

tr_CURR

Rise time for dimming up

CURRx

8.39

tf_CURR

Fall time for dimming down

CURRx

8.39

ton_CURR

On time for CURRx

0.05

4.2

toff_CURR

Off time for CURRx

0.08

8.4

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