Cirrus Logic CS35L32 - Manual (Page 22)

22 DS963F4
CS35L32
4.9 LED Driver
The CS35L32 is driven to flash when FLEN is asserted high. The I 2 C 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
register 3,
Section 7.21 . Its mask is in Section 7.18 . If the error conditions are no longer present, INT is reset and
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).
t
flash
t
flash
FLASH
OFF
FLASH FLASH
Flash
Inhibit
FLASH
t
flash
FLASH
OFF OFF OFF LED CURRENT
FLEN
FLINH
Flash Inhibit
(Timeout_Mode = 1)
Flash
Inhibit
t
flash