DRA790 Datasheet, PDF (163/436 Pages) Texas Instruments – Infotainment Applications Processor

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DRA790, DRA791
DRA793, DRA797
SPRS968A – AUGUST 2016 – REVISED FEBRUARY 2017
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.
CL=
C C _{f1 f2}
(C_f1+C_f2)
Figure 5-13. Load Capacitance Equation
The crystal must be in the fundamental mode of operation and parallel resonant. Table 5-19 summarizes
the required electrical constraints.
Table 5-19. OSC1 Crystal Electrical Characteristics
NAME
DESCRIPTION
f_p
C_f1
C_f2
ESR(C_f1,C_f2)
C_O
L_M
C_M
Parallel resonance crystal frequency
C_f1 load capacitance for crystal parallel resonance with C_f1 = C_f2
C_f2 load capacitance for crystal parallel resonance with C_f1 = C_f2
Crystal ESR
ESR = 30 Ω 19.2 MHz ≤ f_p ≤ 32 MHz
ESR = 40 Ω 19.2 MHz ≤ f_p ≤ 32 MHz
19.2 MHz ≤ f_p ≤ 25 MHz
ESR = 50 Ω 25 MHz < f_p ≤ 27 MHz
27 MHz < f_p ≤ 32 MHz
19.2 MHz ≤ f_p ≤ 23 MHz
Crystal shunt capacitance
ESR = 60 Ω 23 MHz < f_p ≤ 25 MHz
25 MHz < f_p ≤ 32 MHz
19.2 MHz ≤ f_p ≤ 23 MHz
ESR = 80 Ω 23 MHz ≤ f_p ≤ 25 MHz
25 MHz < f_p ≤ 32 MHz
ESR = 100 Ω ^{19.2 MHz ≤ fp ≤ 20 MHz}
20 MHz < f_p ≤ 32 MHz
Crystal motional inductance for f_p = 20 MHz
Crystal motional capacitance
Ethernet and MLB not used
t_j(xiosc1)
Frequency accuracy⁽¹⁾, xi_osc1
Ethernet RGMII and RMII
using derived clock
Ethernet MII using derived
clock
MLB using derived clock
(1) Crystal characteristics should account for tolerance+stability+aging.
MIN
TYP
MAX
Range from 19.2 to 32
12
24
12
24
100
7
5
7
5
Not Supported
7
5
Not Supported
5
3
Not Supported
3
Not Supported
10.16
3.42
±200
UNIT
MHz
pF
pF
Ω
pF
pF
pF
pF
-
pF
pF
-
pF
pF
-
pF
-
mH
fF
±50
ppm
±100
±50
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.
Table 5-20 details the switching characteristics of the oscillator and the requirements of the input clock.
NAME
f_p
Table 5-20. Oscillator Switching Characteristics—Crystal Mode
DESCRIPTION
Oscillation frequency
MIN
TYP
Range from 19.2 to 32
MAX
UNIT
MHz
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Specifications 163