TMS320F28076PZP datasheet(52/192 Pages) TI

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7.9.3.4 Crystal Oscillator

When using a quartz crystal, it may be necessary to include a damping resistor (RD) in the crystal circuit to

prevent over-driving the crystal (drive level can be found in the crystal data sheet). In higher-frequency

applications (10 MHz or greater), RD is generally not required. If a damping resistor is required, RD should be as

small as possible because the size of the resistance affects start-up time (smaller RD = faster start-up time). TI

recommends that the crystal manufacturer characterize the crystal with the application board. Section 7.9.3.4.1

shows the crystal oscillator parameters. Table 7-3 shows the crystal equivalent series resistance (ESR)

requirements. Section 7.9.3.4.2 shows the crystal oscillator electrical characteristics.

7.9.3.4.1 Crystal Oscillator Parameters

MIN

MAX

UNIT

CL1, CL2

Load capacitance

Crystal shunt capacitance

Table 7-3. Crystal Equivalent Series Resistance (ESR) Requirements

CRYSTAL FREQUENCY (MHz)

(1) (2)

MAXIMUM ESR (Ω)

(CL1 = CL2 = 12 pF)

MAXIMUM ESR (Ω)

(CL1 = CL2 = 24 pF)

110

(1)

Crystal shunt capacitance (C0) should be less than or equal to 7 pF.

(2)

ESR = Negative Resistance/3

7.9.3.4.2 Crystal Oscillator Electrical Characteristics

over recommended operating conditions (unless otherwise noted)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Start-up time(1)

f = 20 MHz

ESR MAX = 50 Ω

CL1 = CL2 = 24 pF

C0 = 7 pF

Crystal drive level (DL)

(1)

Start-up time is dependent on the crystal and tank circuit components. TI recommends that the crystal vendor characterize the

application with the chosen crystal.

TMS320F28076, TMS320F28075

SPRS902J – OCTOBER 2014 – REVISED FEBRUARY 2021

www.ti.com

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