Datasheet

SRC4190
SBFS023B
16
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MODE2 MODE1 MODE0 SERIAL PORT MODE
0 0 0 Both Input and Output Ports are Slave mode
0 0 1 Output Port is Master mode with RCKI = 128f
S
0 1 0 Output Port is Master mode with RCKI = 512f
S
0 1 1 Output Port is Master mode with RCKI = 256f
S
1 0 0 Both Input and Output Ports are Slave Mode
1 0 1 Input Port is Master mode with RCKI = 128f
S
1 1 0 Input Port is Master mode with RCKI = 512f
S
1 1 1 Input Port is Master mode with RCKI = 256f
S
TABLE 1. Setting the Serial Port Modes.
REFERENCE CLOCK
The SRC4190 requires a reference clock for operation. The
reference clock is applied at the RCKI input, pin 2. Figure 2
illustrates the reference clock connections and requirements
for the SRC4190. The reference clock may operate at 128f
S
,
256f
S
, or 512f
S
, where f
S
is the input or output sampling
frequency. The maximum external reference clock input
frequency is 50 MHz.
AUDIO PORT MODES
The SRC4190 supports seven serial port modes, which are
shown in Table 1. The audio port mode is selected using the
MODE0 (pin 26), MODE1 (pin 27), and MODE2 (pin 28)
inputs.
In Slave mode, the port LRCK and BCK clocks are config-
ured as inputs, and receive their clocks from an external
audio device. In Master mode, the LRCK and BCK clocks are
configured as outputs, being derived from the reference
clock input (RCKI). Only one port can be set to Master mode
at any given time, as indicated in Table 1.
RST
RCKI
t
RSTL
> 500ns
FIGURE 2. Reference Clock Input Connections and Timing
Requirements.
t
RCKIP
t
RCKIH
t
RCKIL
RCKI
SRC4190
RCKI
From External
Clock Source
50MHz max
2
t
RCKIP
> 20ns min
t
RCKIH
> 0.4 t
RCKIP
t
RCKIL
> 0.4 t
RCKIP
FIGURE 3. Reset Pulse Width Requirement.
RESET AND POWER DOWN OPERATION
The SRC4190 may be reset using the RST input (pin 13).
There is no internal power on reset, so the user should force
a reset sequence after power up in order to initialize the
device. In order to force a reset, the reference clock input
must be active, with an external clock source supplying a
valid reference clock signal (refer to Figure 2). The user must
assert
RST low for a minimum of 500 nanoseconds and then
bring
RST high again to force a reset. Figure 3 shows the
reset timing for the SRC4190.
The SRC4190 also supports a power-down mode. Power-
down mode may be set by holding the
RST input low.
INPUT PORT OPERATION
The audio input port is a three-wire synchronous serial
interface that may operate in either Slave or Master mode.
The SDIN input (pin 4) is the serial audio data input. Audio
data is input at this pin in one of three standard audio data
formats: Philips I
2
S, Left Justified, or Right Justified. The
audio data word length may be up to 24 bits for I
2
S and Left
Justified formats, while the Right Justified format supports
16-, 18-, 20-, or 24-bit data. The data formats are shown in
Figure 4, while critical timing parameters are shown in Figure
5 and listed in the Electrical Characteristics table.
The bit clock is either an input or output at BCKI (pin 5). In
slave mode, BCKI is configured as an input pin, and may
operate at rates from 32f
S
to 128f
S
, with a minimum of one
clock cycle per data bit. In Master mode, BCKI operates at a
fixed rate of 64f
S
.