PCM1770_07 Datasheet, PDF (28/38 Pages) Texas Instruments – LOW-VOLTAGE AND LOW-POWER STEREO AUDIO DIGITAL-TO-ANALOG CONVERTER WITH HEADPHONE AMPLIFIER

PCM1770, PCM1771
SLES011E – SEPTEMBER 2001 – REVISED MARCH 2007
Analog In/Out
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Headphone Output (Stereo)
The PCM1770 and PCM1771 devices have two independent headphone amplifiers, and the amplifier outputs
are provided at the H_OUTL and H_OUTR terminals. Because the capability of the headphone output is designed for
driving a 16-Ω impedance headphone, less than a 16-Ω impedance headphone is not recommended. A resistor
and a capacitor must be connected to H_OUTL and H_OUTR to ensure proper output loading.
Monaural Output (BTL Mode/Monaural Speaker)
The monaural output can be created by summing the left and right headphone outputs. When in the BTL mode,
the user must set the headphone output levels to –3 dB using the ATL[5:0] bits in register 01 and the ATR[5:0]
bits in register 02. Moreover, invert the polarity of the right headphone output by using the RINV bit on control
register 03. The RINV bit is recommended to be 0 during the power-up/-down sequence for minimizing audible
pop noise.
Analog Input
The PCM1770 and PCM1771 devices have an analog input, AIN (terminal 10). The AMIX bit (PCM1770) or the
AMIX terminal (PCM1771) allows the user to mix AIN with the headphone outputs (H_OUTL and H_OUTR) internally.
When in the mixing mode, an ac-coupling capacitor is needed for AIN. But if AIN is not used, AIN must be open
and the AMIX bit (PCM1770) must be disabled or the AMIX terminal (PCM1771) must be low.
Because AIN does not have an internal low-pass filter, it is recommended that the bandwidth of the input signal
into AIN is limited to less than 100 kHz. The source of signals connected to AIN must be connected by low
impedance.
Although the maximum input voltage on AIN is designed to be as large as 0.584 V_HP (peak-to-peak), the user
must attenuate the input voltage on AIN and control the digital input data so that each line output (H_OUTL and
H_OUTR) does not exceed 0.55 V_HP (peak-to-peak) in the mixing mode.
V_COM Output
One unbuffered common-mode voltage output terminal, V_COM, is brought out for decoupling purposes. This
terminal is nominally biased to a dc voltage level equal to 0.5 V_HP and connected to a 10-µF capacitor. In the
case of a capacitor smaller than 10 µF, pop noise can be generated during the power-on/-off or power-up/-down
sequences.
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