AS3677 datasheet(28/68 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

8.4.5 PWM Generator

The PWM generator can be used for any current sink. The setting applies for all current sinks, which are controlled by

the pwm generator (e.g. CURR1 is pwm controlled if curr1_mode = 10). The pwm modulated signal can switch on/off

the current sinks and therefore depending on its duty cycle change the brightness of an attached LED.

Internal PWM Generator

The internal PWM generator uses the 2MHz internal clock as input frequency and its dimming range is 6 bits digital

(2MHz / 2^6 = 31.3kHz pwm frequency) and 2 bits analog. Depending on the actual code in the register pwm_code the

following algorithm is used:

If pwm_code bit 7 = 1

Then the upper 6 bits (Bits 7:2) of pwm_code are used for the 6 bits PWM generation, which controls the selected cur-

rents sinks directly

If pwm_code bit 7 =0 and bit 6 = 1

Then bits 6:1 of pwm_code are used for the 6 bits PWM generation. This signal controls the selected current sinks, but

the analog current of these sinks is divided by 2

If pwm_code bit 7 and bit 6 = 0

Then bits 5:0 of pwm_code are used for the 6 bits PWM generation. This signal controls the selected current sinks, but

the analog current of these sinks is divided by 4

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1. Even by setting 000 for pattern delay, there is a small delay before the new patterns starts.

Table 35. LED Pattern timing

pattern_slow

pattern_delay2 pattern_delay[1..0]

bit duration [ms]

delay [s]

between

patterns

pattern

duration [s]

(total cycle

time:

pattern +

delay)

delay between patterns

pattern_color=0 pattern_color=1

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