Cirrus Logic CS35L32 - Manual (Page 17)

DS963F4 17
CS35L32
4.4 Low-Battery Management
4.3.2 Class G Operation with LEDs On
If LEDs are active, the speaker amplifier supply in one of the following supply modes, as specified by VBOOST_MNG (see
Section 4.10.3 and Section 7.12 for details):
• Class G operation defaults to the higher supply setting: that requested by the LEDs or that requested by Class G.
The latter takes into account both thresholds V
IN1THOF
and V
IN1THON
, as described in Section 4.3.1 .
• Class G disabled and the speaker amplifier supply is set as requested by the LEDs. Thresholds are ignored.
• Class G disabled where the boost converter is in Bypass Mode (VBST = VP). Thresholds are ignored.
• Class G disabled where the boost converter is in Boost Mode and VBST = 5 V. Thresholds are ignored.
4.3.3 Error Conditions
Table 4-2 provides links to error status and mask bits for the Class D audio amplifier errors.
The CS35L32 monitors the OUT± terminals in real time to determine whether the output voltage signal correlates to the
PWM data stream driving the gate drivers internal to the device. If it is not, the CS35L32 interprets the discrepancy as a
short on the outputs, which may have been caused by a short to ground, across the speaker, or to the VBST rail.
If this error occurs, the AMP_SHORT status bit is set, and, if M_AMP_SHORT = 0, INT is asserted. As a result, the device
enters Speaker-Safe Mode, which is described in
Section 4.3.4 .
The CS35L32 also enters Speaker-Safe Mode if its temperature exceeds the overtemperature shutdown threshold
specified in
Table 3-3 . The OTE status bit is set; if M_OTE = 0, INT is asserted.
The amplifier shuts down automatically due to battery (VP) undervoltage, as described in Section 4.5 . The amplifier
restarts automatically upon voltage recovery, with default gain.
The audio amplifier outputs are clamped to ground if MCLK stops, as described in Section 4.13.3 .
4.3.4 Speaker-Safe Mode
Speaker-Safe Mode is entered according to the AMP_SHORT and OTE interrupt status bits as follows:
• In the event of an AMP_SHORT, the CS35L32 mutes the amplifier output to Hi-Z to protect the speaker while the
boost converter is allowed to operate normally.
• In the event of an OTE, the CS35L32 mutes the amplifier output to Hi-Z to protect the speaker and sets the boost
converter in Bypass Mode (VBST = VP). Normal behavior resumes when the error condition ceases and OTE_RLS
is sequenced as described in
Section 4.7.1 .
• If Speaker-Safe Mode is entered as a result of an AMP_SHORT error, normal behavior resumes when the short
condition ceases and the AMP_SHORT_RLS bit is sequenced as described in Section 7.15 .
4.4 Low-Battery Management
Under heavy current loading, such as a high current LED flash event, the battery voltage drops. LOWBAT_TH (see p. 37 )
allows the user to select a voltage threshold, below which flash current is reduced from the LED_FLCUR setting (see p. 43 )
to the LED_FLINHCUR setting (see p. 44 ). Upon voltage recovery above LOWBAT_RECOV (see p. 37 ), the flash current
setting reverts to normal. The user should select a recovery threshold higher than the low-battery threshold.
Low-Battery Mode is entered only if a battery voltage falls below the programmed LOWBAT_TH during a flash event. This
condition is reported by the setting
LOWBAT (see p. 42 ), which can be masked with M_LOWBAT (see p. 41 ).
INT is deasserted after the interrupt registers are cleared by being read, provided the condition no longer exists.
Table 4-2. Class D Audio Amplifier Error Status and Mask Bits
Error Cross-Reference to Description
Amplifier short/Amplifier short mask
Amplifier short release
Overtemperature error/Overtemperature error mask
Overtemperature error release AMP_SHORT p. 41, M_AMP_SHORT p. 40, also see Section 4.3.3
AMP_SHORT_RLS p. 39
OTE p. 41, M_OTE p. 40,
also see Section 4.3.3
OTE_RLS p. 40