TMS320F28076PZP datasheet(49/192 Pages) TI

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7.9.3.2 Clock Frequencies, Requirements, and Characteristics

This section provides the frequencies and timing requirements of the input clocks, PLL lock times, frequencies of

the internal clocks, and the frequency and switching characteristics of the output clock.

7.9.3.2.1 Input Clock Frequency and Timing Requirements, PLL Lock Times

Section 7.9.3.2.1.1 shows the frequency requirements for the input clocks. Table 7-3 shows the crystal

equivalent series resistance requirements. Section 7.9.3.2.1.2 shows the X1 input level characteristics when

using an external clock source. Section 7.9.3.2.1.3 and Section 7.9.3.2.1.4 show the timing requirements for the

input clocks. Section 7.9.3.2.1.5 shows the PLL lock times for the Main PLL and the USB PLL.

7.9.3.2.1.1 Input Clock Frequency

MIN

MAX

UNIT

f(XTAL)

Frequency, X1/X2, from external crystal or resonator

MHz

f(X1)

Frequency, X1, from external oscillator

MHz

f(AUXI)

Frequency, AUXCLKIN, from external oscillator

MHz

7.9.3.2.1.2 X1 Input Level Characteristics When Using an External Clock Source (Not a Crystal)

over recommended operating conditions (unless otherwise noted)

PARAMETER

MIN

MAX

UNIT

X1 VIL

Valid low-level input voltage

–0.3

0.3 * VDDIO

X1 VIH

Valid high-level input voltage

0.7 * VDDIO

VDDIO + 0.3

7.9.3.2.1.3 X1 Timing Requirements

MIN

MAX

UNIT

tf(X1)

Fall time, X1

tr(X1)

Rise time, X1

tw(X1L)

Pulse duration, X1 low as a percentage of tc(X1)

45%

55%

tw(X1H)

Pulse duration, X1 high as a percentage of tc(X1)

45%

55%

7.9.3.2.1.4 AUXCLKIN Timing Requirements

MIN

MAX

UNIT

tf(AUXI)

Fall time, AUXCLKIN

tr(AUXI)

Rise time, AUXCLKIN

tw(AUXL)

Pulse duration, AUXCLKIN low as a percentage of tc(XCI)

45%

55%

tw(AUXH)

Pulse duration, AUXCLKIN high as a percentage of tc(XCI)

45%

55%

7.9.3.2.1.5 PLL Lock Times

MIN

NOM

MAX

UNIT

t(PLL)

Lock time, Main PLL (X1, from external oscillator)

50 µs + 2500 * tc(OSCCLK) (1)

µs

t(USB)

Lock time, USB PLL (AUXCLKIN, from external oscillator)

50 µs + 2500 * tc(OSCCLK) (1)

µs

(1)

The PLL lock time here defines the typical time of execution for the PLL workaround as defined in the TMS320F2807x MCUs Silicon

Errata . Cycle count includes code execution of the PLL initialization routine, which could vary depending on compiler optimizations

and flash wait states. TI recommends using the latest example software from C2000Ware for initializing the PLLs. For the system PLL,

see InitSysPll() or SysCtl_setClock(). For the auxillary PLL, see InitAuxPll() or SysCtl_setAuxClock().

www.ti.com

TMS320F28076, TMS320F28075

SPRS902J – OCTOBER 2014 – REVISED FEBRUARY 2021

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