ALED7709ATR datasheet(36/63 Pages) STMICROELECTRONICS

36 / 63 page

7.14.7

Working mode M7 (Reg DIMCFG = 00xxx101b)

PWMI is sampled to recover duty-cycle and frequency to be applied to all the outputs; frequency is set as for

Table 13 while duty-cycle sets the output pulse duration following the exponential curve.

All the outputs go to OFF if the PWMI signal stays at LOW level for more than 20 ms.

Current can be set differently for each channel acting on the proper channel register GAINx.

7.14.8

Working mode M8 (Reg DIMCFG = 01xxxx01b)

PWMI directly controls the digital behavior of outputs; the PWMI signal is reconstructed by the internal clock but it

is not post-processed and so the LECC bit has no meaning.

Current can be set differently for each channel acting on the proper channel register GAINx.

7.14.9

Working mode M9 (Reg DIMCFG = 1xXXX000b)

PWM frequency is set by FDIM[2:0] bits as for Table 31 description while the PWM for all the outputs is defined by

registers PWM1H and PWM1L. The duty-cycle value written in the PWM1 registers is applied as is (liner curve) to

all the channels.

Current is set for all the channels by the register GAIN1 value.

7.14.10

Working mode M10 (Reg DIMCFG = 1xXXX100b)

PWM frequency is set by FDIM[2:0] bits as for Table 31 description while the PWM for all the outputs is defined by

to all the channels.

Current is set for all the channels by the register GAIN1 value.

7.14.11

Working mode M11 (Reg DIMCFG = 1xXXX010b)

PWM frequency is set by FDIM[2:0] bits as for Table 31 description.

Being in mixed dimming mode, the value written in registers BRIGHT is used to compute both analog current and

PWM settings that are applied to all the channels. The conversion is based on linear curve.

Hereafter, a couple of examples to clarify the mode behavior, transition point is set to 25%:

BRIGHT registers are programmed for setting 15%

because of the linear curve application, the 16-bit value in BRIGHT registers is exactly the

brightness value to be considered, which results to be below the defined TP

GAIN1, valid for all channels, is set at 25% of maximum

PWM is set to a duty-cycle of 60% because to have 15% brightness with current set to 25% we need

to multiply by 4 the PWM

BRIGHT registers are programmed for setting 60%

because of the linear curve application, the 16-bit value in BRIGHT registers is exactly the

brightness value to be considered, which results to be above the defined TP

GAIN1, valid for all channels, is set at 60% of maximum

PWM is set at 100%, outputs always ON

7.14.12

Working mode M12 (Reg DIMCFG = 1xXXX110b)

PWM frequency is set by FDIM[2:0] bits as for Table 31 description.

Being in mixed dimming mode the value written in register BRIGHT is used to compute both analog current and

PWM settings that are applied to all the channels. The conversion is based on exponential curve and so only the

8-bit value in BRIGHT%L is considered for the final brightness computation.

Hereafter, a couple of examples to clarify the mode behavior, transition point is set to 25%:

BRIGHT%L register is programmed for setting 65%

because of the exponential curve application, the 8-bit value in BRIGHT%L register becomes 2.9%

brightness as value to be considered, which results to be below the defined TP

GAIN1, valid for all channels, is set at 25% of maximum

PWM is set to a duty-cycle of 11.6%; because to have 2.9% brightness with current set to 25% we

need to multiply by 4 the PWM

ALED7709

Table of different working modes

DS14214 - Rev 1

page 36/63

ALED7709ATR Datasheet(PDF) 36 Page - STMicroelectronics

ALED7709ATR Datasheet(HTML) 36 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Datasheet Download

Link URL