160
AM5706, AM5708
SPRS961B –AUGUST 2016–REVISED SEPTEMBER 2017
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Specifications Copyright © 2016–2017, Texas Instruments Incorporated
NOTE
The load capacitors, C
f1
and C
f2
in Figure 5-12, should be chosen such that the below
equation is satisfied. C
L
in the equation is the load specified by the crystal manufacturer. All
discrete components used to implement the oscillator circuit should be placed as close as
possible to the associated oscillator xi_osc1, xo_osc1, and vssa_osc1 pins.
Figure 5-13. Load Capacitance Equation
The crystal must be in the fundamental mode of operation and parallel resonant. Table 5-21 summarizes
the required electrical constraints.
Table 5-21. OSC1 Crystal Electrical Characteristics
NAME DESCRIPTION MIN TYP MAX UNIT
f
p
Parallel resonance crystal frequency Range from 19.2 to 32 MHz
C
f1
C
f1
load capacitance for crystal parallel resonance with C
f1
= C
f2
12 24 pF
C
f2
C
f2
load capacitance for crystal parallel resonance with C
f1
= C
f2
12 24 pF
ESR(C
f1
,C
f2
) Crystal ESR 100 Ω
C
O
Crystal shunt capacitance
ESR = 30 Ω 19.2 MHz ≤ f
p
≤ 32 MHz 7 pF
ESR = 40 Ω 19.2 MHz ≤ f
p
≤ 32 MHz 5 pF
ESR = 50 Ω
19.2 MHz ≤ f
p
≤ 25 MHz 7 pF
25 MHz < f
p
≤ 27 MHz 5 pF
27 MHz < f
p
≤ 32 MHz Not Supported -
ESR = 60 Ω
19.2 MHz ≤ f
p
≤ 23 MHz 7 pF
23 MHz < f
p
≤ 25 MHz 5 pF
25 MHz < f
p
≤ 32 MHz Not Supported -
ESR = 80 Ω
19.2 MHz ≤ f
p
≤ 23 MHz 5 pF
23 MHz ≤ f
p
≤ 25 MHz 3 pF
25 MHz < f
p
≤ 32 MHz Not Supported -
ESR = 100 Ω
19.2 MHz ≤ f
p
≤ 20 MHz 3 pF
20 MHz < f
p
≤ 32 MHz Not Supported -
L
M
Crystal motional inductance for f
p
= 20 MHz 10.16 mH
C
M
Crystal motional capacitance 3.42 fF
t
j(xiosc1)
Frequency accuracy
(1)
, xi_osc1
Ethernet and MLB not used ±200
ppm
Ethernet RGMII and RMII
using derived clock
±50
Ethernet MII using derived
clock
±100
(1) Crystal characteristics should account for tolerance+stability+aging.
When selecting a crystal, the system design must take into account the temperature and aging
characteristics of a crystal versus the user environment and expected lifetime of the system.
Table 5-22 details the switching characteristics of the oscillator and the requirements of the input clock.
Table 5-22. Oscillator Switching Characteristics—Crystal Mode
NAME DESCRIPTION MIN TYP MAX UNIT
f
p
Oscillation frequency Range from 19.2 to 32 MHz
t
sX
Start-up time 4 ms
