RL1632R-R100-F datasheet(11/22 Pages) ONSEMI

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NCV78514

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DCDC OFF

100 % Duty Cycle

ILED = ISET

AUTOMODE

Logarithmic rising

DIM = 1 for more P_DIM_DETECT

FADING_TIME elapsed

DIM = 0 longer than DIM_DETECT

AUTOMODE

Logarithmic falling

DIM=0 longer than DIM_DETECT

FADING_TIME elapsed

Digital mode

DCDC duty cycle =

DIM duty cycle

Linear transition

Rising or falling

FADING_TIME ratio

DIM = 100% duty cycle

DIM = Duty cycle

DIM = Valid Duty cycle

Valid Duty cycle change

Linear transition done

DIM = 0 for P_DIM_DETECT or

Figure 6. Dimming Modes Functional Flow Diagram

Important remark:

For EMC conductive emission performance, Pi filters

must be placed on:

 BAT line

 and recommended on the output of the DCDC

converter (after the Rsense resistor), in case of separate

module application.

The sizing of the Pi filters (please see the bill of material)

is done to achieve a good stability of the Buck − Boost.

Any other component choice will have an impact on the

turn on time in dimming mode, as for the duty cycle accuracy

(DIM_DC_ACC) or overall stability.

The turn on time in Normal Mode and DIM Mode are

respectively

FULL_STARTUP

and

DIMMING_STARTUP.

Upon removal of the DIM signal, the LED current is

turned off only after a delay of DIM_MISS.

LED CURRENT SETTING

RSET Pull Down

The LED current is set through the ISET pin, with

a pull−down resistor

Granularity of the current setting is achieved though the

resistor series choice and tolerance of them.

ILED (A) +

1000 (W @ A)

RSET (W)

) 0.1 (A)

(eq. 1)

For example, RSET = 1 k

W => 1.1 A.

The identification of the RSET is initiated by BAT >

P_UVLO_STARTING, rising edge.

During IC’s wake up time, a first read of RSET is

performed in order to provide current into LEDs within the

P_FULL_STARTUP. The RSET is continuously done

during P_SET_RSET to achieve the more accurate value in

this time frame. After this period, a value out of the

P_RSET_RANGE, longer than P_TIMEOUT_RSET is

considered as an out of range, and LED current is turned off.

A new power on reset sequence is then required.

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