92hd99 Integrated Device Technology, 92hd99 Datasheet - Page 27

• Manufacturer Part Number: 92hd99
• Description: Single Chip Pc Audio System Codec+speaker Amplifier+capless Hp+ldo
• Manufacturer: Integrated Device Technology

92HD99
SINGLE CHIP PC AUDIO SYSTEM, CODEC+SPEAKER AMPLIFIER+CAPLESS HP+LDO
IDT CONFIDENTIAL
©2009 INTEGRATED DEVICE TECHNOLOGY, INC.
2.16. Headphone Drivers
2.17. BTL Amplifier
2.18. BTL Amplifier High-Pass Filter
SYNC rate) / (4*Divider), producing tones from 47 Hz to 12 kHz (logarithmic scale). Other audio
sources are disabled when digital PC_Beep is active.
It should be noted that digital PC Beep is disabled if the divider = 00h.
PC-Beep may be attenuated and distorted when the CODEC is in D3 depending on the load imped-
ance seen by the output amplifier since all ports are in a low power state while in D3. Load imped-
ances of 10K or larger can support full scale outputs but lower impedance loads will distort unless
the output amplitude is reduced. Digital PC_Beep requires a clock to operate and the CODEC will
prevent the system from stopping the bus clock while in D3 by setting the Clock_Stop_OK bit to 0 to
indicate that the part requires a clock.
The codec implements both traditional and cap-less headphone outputs. The Microsoft Windows
Logo Program allows up to the equivalent of 100ohms in series. However, an output level of +3dBV
at the pin is required to support 300mV at the jack with a 32ohm load and 1V with a 320 ohm load.
Microsoft allows device and system manufactures to limit output voltages to address EU safety
requirements. (WLP 3.09 - please refer to the latest Windows Logo Program requirements from
Microsoft.) The codec does not support power limiting.
Headphone performance will degrade if more than one port is driving a 32 ohm load.
An integrated class-D stereo BTL amplifier is provided to directly drive 4 ohm speakers (2W @
4.75V) or 8 ohm speakers (1W @ 4.75V). No external filter is needed for cable runs of 18” or less.
An internal DC blocking filter prevents distortion when the audio source has DC content, and pre-
vents unintentional power consumption when pausing audio playback. The amplifier may be con-
trolled using the EAPD pin (see EAPD section.)
Using a vendor specific verb, the BTL amplifier may be configured to support a mono speaker con-
nected to the L +/- pins. In this mode, the Left and Right audio is mixed and sent to the left output
only. The right channel is turned off to conserve power.
Maximum gain for the BTL amplifier is programmable. The following 4 gain settings relative to a
nominal line output are desired: +6.5dB, +9.5dB, +14.5dB, +16.5dB. Absolute gain may vary and the
suggested accuracy is +/-1.5dB.
This gain is exposed in a vendor specific widget and is intended to mimic the pin programmable gain
implemented in discrete BTL amplifiers commonly used in notebook computers.
The BTL amplifier includes thermal management circuitry. When the CODEC reaches a temperature
of about 140 degrees, the output amplitude of the BTL amp is gradually lowered until the tempera-
ture falls below 140. All other functions will remain active if the BTL amplifier is shut down due to die
temperature.
For mobile applications, speakers are often incapable of reproducing low frequency audio and
unable to handle the maximum output power of the BTL amplifier. A high-pass filter is implemented
in the BTL output path to reduce the amount of low frequency energy reaching speakers attached to
the BTL amplifier. This can prevent speaker failure.
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