AM6548, AM6528, AM6526
ZHCSLA7B –DECEMBER 2019 –REVISED JUNE 2021
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Cf1Cf2
= (Cf1+Cf2)
C
L
SPRS932_CLOCK_03
图7-20. Load Capacitance Equation
The crystal must be in the fundamental mode of operation and parallel resonant. 表 7-18 summarizes the
required electrical constraints.
表7-18. OSC1 Crystal Electrical Characteristics
NAME
DESCRIPTION
MIN
TYP
MAX UNIT
fp
Parallel resonance crystal frequency
19.2, 20, 24, 25, 26, 27
MHz
24 pF
24 pF
Cf1
Cf2
Cf1 load capacitance for crystal parallel resonance with Cf1 = Cf2
Cf2 load capacitance for crystal parallel resonance with Cf1 = Cf2
12
12
ESR(Cf1,Cf2) Crystal ESR
100
Ω
pF
pF
pF
pF
-
CO
Crystal shunt capacitance
19.2 MHz, 20 MHz, 24 MHz, 25
MHz, 26 MHz, 27 MHz
7
ESR = 30 Ω
ESR = 40 Ω
19.2 MHz, 20 MHz
7
5
ESR = 50 Ω
ESR = 60 Ω
ESR = 80 Ω
ESR = 100 Ω
24 MHz, 25 MHz, 26 MHz, 27
MHz
19.2 MHz, 20 MHz
7
5
3
24 MHz, 25 MHz, 26 MHz, 27
MHz
Not Supported
Not Supported
Not Supported
19.2 MHz, 20 MHz
pF
-
24 MHz, 25 MHz, 26 MHz, 27
MHz
19.2 MHz, 20 MHz
pF
-
24 MHz, 25 MHz, 26 MHz, 27
MHz
LM
Crystal motional inductance for fp = 20 MHz
10.16
3.42
mH
fF
CM
Crystal motional capacitance
Frequency accuracy, OSC1_XI
fj(OSC1_XI)
Ethernet RGMII and RMII not
used
±100
±50
ppm
Ethernet RGMII and RMII using
derived clock
When selecting a crystal, the system design must consider the temperature and aging characteristics of a based
on the worst case environment and expected life expectancy of the system.
表7-19 details the switching characteristics of the oscillator and the requirements of the input clock.
表7-19. OSC1 Switching Characteristics –Crystal Mode
NAME
DESCRIPTION
MIN
TYP
MAX
UNIT
MHz
ms
fp
Oscillation frequency
Start-up time
19.2, 20, 24, 25, 26, 27
tsX
2(1)
(1) In order to meet the start-up time defined in this table, the crystal needs to be selected according to the following equation:
Tsu = K×Lm/ (Ro-ESR) + Δt
where Lm is crystal motional inductance, RO is the negative resistance of amplifier, ESR is the crystal Effective series resistance and K
is a constant which represents the initial conditions. Δt is the time amplifier takes to reach its bias point after power down is released.
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