SPRS950F December 2015 – May 2019 DRA745 , DRA746 , DRA750 , DRA756
PRODUCTION DATA.
Refer to the PDF data sheet for device specific package drawings
An external crystal is connected to the device pins. Figure 6-6 describes the crystal implementation.
NOTE
The load capacitors, Cf1 and Cf2 in Figure 6-6, should be chosen such that the below equation is satisfied. CL 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.
The crystal must be in the fundamental mode of operation and parallel resonant. Table 6-5 summarizes the required electrical constraints.
NAME | DESCRIPTION | MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|---|---|
fp | Parallel resonance crystal frequency | Range from 19.2 to 32 | MHz | ||||
Cf1 | Cf1 load capacitance for crystal parallel resonance with Cf1 = Cf2 | 12 | 24 | pF | |||
Cf2 | Cf2 load capacitance for crystal parallel resonance with Cf1 = Cf2 | 12 | 24 | pF | |||
ESR(Cf1,Cf2) | Crystal ESR | 100 | Ω | ||||
CO | Crystal shunt capacitance | ESR = 30 Ω | 19.2 MHz≤fp≤32 MHz | 7 | pF | ||
ESR = 40 Ω | 19.2 MHz≤fp≤32 MHz | 5 | pF | ||||
ESR = 50 Ω | 19.2 MHz≤fp≤25 MHz | 7 | pF | ||||
25 MHz<fp≤27 MHz | 5 | pF | |||||
27 MHz<fp≤32 MHz | Not Supported | - | |||||
ESR = 60 Ω | 19.2 MHz≤fp≤23 MHz | 7 | pF | ||||
23 MHz<fp≤25 MHz | 5 | pF | |||||
25 MHz<fp≤32 MHz | Not Supported | - | |||||
ESR = 80 Ω | 19.2 MHz≤fp≤23 MHz | 5 | pF | ||||
23 MHz≤fp≤25 MHz | 3 | pF | |||||
25 MHz<fp≤32 MHz | Not Supported | - | |||||
ESR = 100 Ω | 19.2 MHz≤fp≤20 MHz | 3 | pF | ||||
20 MHz<fp≤32 MHz | Not Supported | - | |||||
LM | Crystal motional inductance for fp = 20 MHz | 10.16 | mH | ||||
CM | Crystal motional capacitance | 3.42 | fF | ||||
tj(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 | ||||||
MLB using derived clock | ±50 |
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 6-6 details the switching characteristics of the oscillator and the requirements of the input clock.
NAME | DESCRIPTION | MIN | TYP | MAX | UNIT |
---|---|---|---|---|---|
fp | Oscillation frequency | Range from 19.2 to 32 | MHz | ||
tsX | Start-up time | 4 | ms |