CS35L32 datasheet(22/51 Pages) CIRRUS

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DS963F5

CS35L32

4.9 LED Driver

The CS35L32 is driven to flash when FLEN is asserted high. The I2C interface allows a host to program Flash and Movie

Mode currents, as well as a flash timer. The corresponding registers for these settings are LED_FLCUR (see p. 43), LED_

MVCUR (see p. 44), and TIMER (see p. 44). The flash event terminates at the end of a period determined by the flash

timer and optionally when FLEN is deasserted; this option is configured through TIMEOUT_MODE (see p. 44).

Flash current is reduced if FLINH is asserted. Currents in both channels are reduced to the LED_FLINHCUR setting (see

p. 44). If FLINH is deasserted, the current reverts to the LED_FLCUR setting, subject to the flash timer state.

Movie Mode operation has no timer and starts and ends according to the LED_MVCUR setting. Fig. 4-7 shows how Flash

and Flash Inhibit Mode currents are started and terminated.

To power the LED load, the LED driver and current regulator automatically boost the voltage if battery operation is

insufficient to produce the required LED currents. The controller bases whether to boost or operate in bypass, based on

maintaining a minimum voltage across the current regulator. The boost voltage varies by up to 5 V nominal, as described

in Section 4.10 and Section 7.12, depending on user selection.

Figure 4-7. LED Flash Timing Diagram

4.9.1

LED Driver Protection

The LED controller shuts down if the CS35L32’s temperature exceeds the overtemperature shutdown threshold specified

in Table 3-3. The OTE status bit is set and, and if M_OTE = 0, INT is asserted. Recovery starts after the user clears OTE_

RLS (see p. 40), after which, the LED drivers must be retriggered with a FLEN signal for a flash event to occur, or with the

LEDx_MVEN enable bit (see Section 7.24) for a Movie Mode event to occur.

An automatic LED driver shutdown occurs in the event of a shorted or open LED. LED open and short conditions are

detected only when a Flash or Movie Mode event is initiated. For a Flash Mode event to occur after clearing the error status

bit, the LED drivers must be retriggered with a FLEN signal. For a Movie Mode event to occur after clearing the error status

bit, the LEDx_MVEN bit must be set.

4.9.2

LED Driver Interrupt

An interrupt is generated when any of the following conditions or faults occur: LEDx short or open is present when a Flash

event is initiated, current limit, boost output overvoltage, or UVLO of VP. The condition is registered in interrupt status

deasserted after the interrupt register is read.

Note:

The device does not generate an LED open circuit interrupt if the boost converter is running in bypass mode

(PDN_BST= 01).

tflash

FLASH

OFF

FLASH

Flash

Inhibit

FLASH

tflash

FLASH

OFF

LED CURRENT

FLEN

FLINH

Flash Inhibit

(Timeout_Mode = 1)

Flash

Inhibit

tflash

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