Cirrus Logic CS35L32 - Manual (Page 23)

DS963F4 23
CS35L32
4.10 Power Budgeting
4.9.3 LED Lighting Status Register
The LED lighting status register (see Section 7.22 ) reports the state of LEDs and their controls. Status is reported for LED1
and LED2 flash events, indicating whether each LED is driven with current set by the flash setting. Likewise, status is
reported for LED1 and LED2 Movie Mode events, indicating whether each LED is driven with current set by the Movie
Mode setting. LED2 disable status is reported if FLOUT2 is used without an LED and is tied to ground, as shown in
Fig. 2-1 . The logic status of the signal input at FLEN and FLINH is reported. Flash timer events are reported.
4.10 Power Budgeting
Power budgeting is configured through ILED_MNG , AUDIOGAIN_MNG , and VBOOST_MNG (see p. 38 ), which set the
boost converter’s output mode and the load management mode, as described in Section 4.10.1 – Section 4.10.3 . Load
management consists of reducing audio or LED load, or both, as long as one of the following conditions exists:
• The boost converter output voltage has dropped, provided that the boost converter is configured for a fixed 5-V
Mode through VBOOST_MNG and the load current has settled to its target value.
• The boost converter is in current limit.
• An overtemperature warning (135°C) has occurred.
Power budgeting is configurable to be active automatically without user intervention, semiautomatically, or
nonautomatically, where the user controls audio and LED load management.
Fig. 4-8 shows power budgeting.
Figure 4-8. Power Budgeting Block Diagram
4.10.1 Audio-Only Operation
If only audio is operating, there are no power-budgeting concerns. As a default, the boost converter’s output voltage is
fixed in Bypass Mode (VBST = VP). The user can set
VBOOST_MNG (see p. 38 ) to any of the nondefault modes for a
different boost behavior. Refer to Section 4.3.1 .
4.10.2 LED-Only Operation
If only LEDs are operating, the user can select one the following courses of action:
• By clearing ILED_MNG (see p. 38 ), LED current is managed automatically. If the CS35L32 enters load
management mode due to a condition listed in Section 4.10 , the current is iteratively reduced until the condition no
longer exists.
• By setting ILED_MNG, the user maintains full control over LED current.
As a default, the boost converter’s output voltage is fixed in Bypass Mode (VBST = VP). The user can set VBOOST_MNG
to any of the nondefault modes for a different boost behavior. In particular, if VBOOST_MNG = 00 or 01 and load power
consists of LEDs only, the CS35L32 adapts for low power dissipation by automatically reducing the LED driver voltage
(Vds) at pins FLOUT1 and FLOUT2 and by reducing the boost converter’s output voltage. Such operation increases boost
converter efficiency, lowers temperature rise in the CS35L32, and increases battery run time. If VBOOST_MNG is set to
10 or 11, the CS35L32 does not adapt for low-power dissipation because the boost voltage is fixed.
Flash LED
Current Drivers
IN– –
+ IN+
Class D Amplifier
Overtemperature
Warning
Power Budgeting
Controller
Vds Monitor
Boost Drop
Current Limit
Boost Converter
OTW on p. 41