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SLES081A − JUNE 2003 – REVISED MAY 2004
DETAILED DESCRIPTION
CLOCK AND RESET
For both USB function and audio function, the PCM2704/5/6/7 requires a 12-MHz (±500 ppm) clock, which can be
generated by the built-in oscillator using a 12-MHz crystal resonator. The 12-MHz crystal resonator must be
connected to XTI (pin 28 for PCM2704/5, pin 12 for PCM2706/7) and XTO (pin 1 for PCM2704/5, pin 13 for
PCM2706/7) with one large (1-MΩ) resistor and two small capacitors, the capacitance of which depends on the
specified load capacitance of the crystal resonator. An external clock can be supplied from XTI (pin 28 for
PCM2704/5, pin 12 for PCM2706/7). If an external clock is supplied, XTO (pin 1 for PCM2704/5, pin 13 for
PCM2706/7) must be left open. Because no clock disabling pin is provided, it is not recommended to use the external
clock supply. SSPND (pin 27 for PCM2704/5, pin 11 for PCM2706/7) is unable to use clock disabling.
The PCM2704/5/6/7 has an internal power-on reset circuit, and it works automatically when V
(pin 7 for
(pin 10 for
DD
PCM2704/5, pin 21 for PCM2706/7) exceeds 2 V typical (1.6 V–2.4 V), which is equivalent to V
BUS
PCM2704/5, pin 24 for PCM2706/7) exceeding 3 V typical for bus-powered applications. About 700 µs is required
until internal reset release.
OPERATION MODE SELECTION
The PCM2704/5/6/7 has the following mode-select pins.
Power Configuration Select/Host Detection
PSEL (pin 4 for PCM2704/5, pin 16 for PCM2706/7) is dedicated to selecting the power source. This selection affects
the configuration descriptor. While in bus-powered operation, maximum power consumption from the V
is
BUS
determined by HOST (pin 21 for PCM2704/5, pin 3 for PCM2706/7). For self-powered operation, HOST must be
connected to V of the USB bus with a pulldown resistor to detect attach and detach. (To avoid excessive suspend
BUS
current, the pulldown should be a high-value resistor.)
Table 1. Power Configuration Select
PSEL
DESCRIPTION
Self-powered
Bus-powered
0
1
HOST
DESCRIPTION
0
1
Detached from USB (self-powered)/100 mA (bus-powered)
Attached to USB (self-powered)/500 mA (bus-powered)
Function Select (PCM2706/7)
2
FSEL (pin 9) determines the function of FUNC0–FUNC3 (pins 4, 5, 18, and 19) and DOUT (pin17). When the I S
interface is required, FSEL must be set to LOW. Otherwise, FSEL must be set to HIGH.
Table 2. Function Select
FSEL
DOUT
FUNC0
FUNC1
FUNC2
FUNC3
2
2
2
2
2
0
1
Data out (I S)
LRCK (I S)
BCK (I S)
SYSCK (I S)
(1)
Data in (I S)
(1)
(1)
(1)
Play/pause (HID)
S/PDIF data
Next track (HID)
Previous track (HID)
Stop (HID)
(1)
Valid on the PCM2706; no function assigned on the PCM2707.
15
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