DETAILED DESCRIPTION
Clock and Reset
Operation Mode Selection
Power Configuration Select/Host Detection
Function Select (PCM2706/7)
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SLES081F – JUNE 2003 – REVISED JANUARY 2009
For both USB and audio functions, 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-M
Ω
) 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
DD
(pin 7 for
PCM2704/5, pin 21 for PCM2706/7) exceeds 2 V typical (1.6 V–2.4 V), which is equivalent to V
BUS
(pin 10 for
PCM2704/5, pin 24 for PCM2706/7) exceeding 3 V typical for bus-powered applications. Approximately 700
µ
s is
required until internal reset release.
The PCM2704/5/6/7 has the following mode-select pins.
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 V
BUS
is
determined by HOST (pin 21 for PCM2704/5, pin 3 for PCM2706/7). For self-powered operation, HOST must be
connected to V
BUS
of the USB bus with a pulldown resistor to detect attach and detach. (To avoid excessive
suspend current, the pulldown should be a high-value resistor.)
Table 1. Power Configuration Select
PSEL
DESCRIPTION
0
Self-powered
1
Bus-powered
HOST
DESCRIPTION
0
Detached from USB (self-powered)/100 mA (bus-powered)
1
Attached to USB (self-powered)/500 mA (bus-powered)
FSEL (pin 9) determines the function of FUNC0–FUNC3 (pins 4, 5, 18, and 19) and DOUT (pin17). When the I
2
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
0
Data out (I
2
S)
LRCK (I
2
S)
BCK (I
2
S)
SYSCK (I
2
S)
Data in (I
2
S)
1
S/PDIF data
Next track (HID)
(1)
Previous track (HID)
(1)
Stop (HID)
(1)
Play/pause (HID)
(1)
(1)
Valid on the PCM2706; no function assigned on the PCM2707.
Copyright © 2003–2009, Texas Instruments Incorporated
15
Product Folder Link(s):
PCM2704 PCM2705 PCM2706 PCM2707
