LM49352RLX/NOPB National Semiconductor, LM49352RLX/NOPB Datasheet - Page 51

• Manufacturer Part Number: LM49352RLX/NOPB
• Description: IC AMP AUDIO MONO D1.4W 36USMD
• Manufacturer: National Semiconductor
• Series: Boomer®, PowerWise®r
• Type: Class Dr

Specifications of LM49352RLX/NOPB

• Output Type: 1-Channel (Mono) with Mono and Stereo Headphones
• Max Output Power X Channels @ Load: 1.4W x 1 @ 8 Ohm; 65mW x 2 @ 32 Ohm
• Features: Depop, Differential Inputs, I²C, I²S, Microphone, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 36-MicroSMDxt
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Other names: LM49352RLX

Headphone Detection Circuit
The LM49352 features a headphone detection circuit (HDC) that automatically enables the headphone amplifier whenever the
insertion of a headphone plug is detected and disables the headphone amplifier during the removal of a headphone plug. The HDC
optimizes power management by automatically disabling any output amplifier that is not in use. The HDC eliminates the necessity
of polling the I
2
C bus for status changes. However, since the HDC requires the use of the GPIO pin, the PORT2_SDO functionality
sensing is required.
The HDC requires a headphone jack with a normally closed mechanical switch and a pullup resistor, R
, tied between the me-
PU
chanical switch and I/O_V
(Refer to Figure 14). Choosing a R
value of at least 500kΩ ensures minimal current draw through
DD
PU
the pullup resistor. When the headphone amplifier is disabled, an internal 50kΩ pulldown, R
, is connected to each headphone
PD
amplifier output. Without the presence of a headphone plug, the headphone jack’s mechanical switch is closed thereby connecting
the right headphone amplifier output to R
. The GPIO pin detects a logic low level due to the voltage division between R
and
PU
PU
R
. When the GPIO pin is set to HPSENSE mode, a logic low voltage reading causes the HDC to disable the headphone amplifier.
PD
When a headphone plug is inserted, the mechanical connection between R
and R
is broken, resulting in a logic high level
PU
PD
detected by the GPIO pin. A logic high voltage reading causes the HDC to enable the headphone amplifier.
The HDC has four modes of operation that automatically enable/disable different combinations of the audio output amplifiers
contained within the LM49352. Having the choice of four different HDC settings maximizes power management flexibility to suit a
particular application. Please refer to the HP_SENSE (reg 0x1Bh) register table for a detailed discussion on the different HDC
modes of operation.
30072793
FIGURE 15. Application Circuit for Headphone Detection
51
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