48
DS1113F1
CS4399
5 Applications
5 Applications
This section provides recommended application procedures and instruction sequences for standard CS4399 operations.
5.1 PLL Clocking
Data-path logic is in the MCLK_INT domain, where MCLK_INT is expected to be 22.5792 or 24.576 MHz. For clocking
scenarios in which the external system MCLK provided to CS4399 is neither 22.5792 nor 24.576 MHz, the PLL must be
turned on to provide the desired internal MCLK. At start up, the system uses RCO as the internal MCLK for PLL
programming over I
2
C and switches to the PLL output after it settles. PLL start-up time is a maximum of 1 ms.
5.2 Power Sequencing
Note the following for power-up sequencing on the CS4399:
• VP must be powered up first.
• All other supplies can come up in any order before RESET is released.
Note the following for power-down sequencing on the CS4399:
• After RESET is asserted, VA/VCP/VL/VD can be removed in any order.
• VP must be powered down last.
5.3 Crystal Tuning
The CS4399 uses an external crystal as the source for internal MCLK. Refer to
is supported by CS4399.
lists supported crystals that meet the requirements for CS4399 and also shows also
shows the XTAL_IBIAS settings for different crystals.
The crystal setting register (0x20052) must be set appropriately based on the crystal used.
The frequency at which the crystal eventually oscillates can be calculated using the formula below:
F
osc
= 1/(2*
π
*sqrt[Lm*(C
m
(C
0
+C
L
))/(C
m
+C
0
+C
L
)]) ,
where
L
m
= motional inductance of crystal
C
m
= motional capacitance of crystal
C
0
= shunt capacitance
C
L
= load capacitance
Trace capacitance and pad capacitance (approximately 0.5 pF) must also be taken into account while calculating the value
of the load capacitors. Below are the steps to tune the crystal to the correct frequency:
1. Select load capacitor values that match the load capacitance spec in crystal manufacturer's data sheet.
Table 5-1. Example List of Supported Crystals
Manufacturer
1
1.Contact your local Cirrus Logic representative for a list of supported manufacturers and part numbers.
Part Number
Frequency (MHz)
Bias Current
Strength (µA)
Crystal Setting Register
(0x20052)
River Electronics
FCX-06-22.5792J51933
22.5792
12.5
0x04
FCX-06-24.5760J51930
24.576
7.5
0x06
NDK
NX2016SA 22.5792M EXS00A-CS09116
22.5792
15
0x02
NX2016SA 24.576M EXS00A-CS09117
24.576
TXC
8Y22570001
22.5792
12.5
0x04
8Y24570001
24.576