AM625 datasheet(122/255 Pages) TI

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7.11.4.1.3 WKUP_LFOSC0 Internal Oscillator Clock Source

Figure 7-21 shows the recommended crystal circuit. It is recommended that preproduction printed-circuit board

(PCB) designs include the two optional resistors Rbias and Rd in case they are required for proper oscillator

operation when combined with production crystal circuit components. In most cases, Rbias is not required and

Rd is a 0-Ω resistor. These resistors may be removed from production PCB designs after evaluating oscillator

performance with production crystal circuit components installed on preproduction PCBs.

Device

WKUP_LFOSC0_XO

WKUP_LFOSC0_XI

Crystal

(Optional)

J7ES_LF_OSC_INT_12

Rbias

(Optional)

PCB Ground

Figure 7-21. WKUP_LFOSC0 Crystal Implementation

Table 7-21 presents LFXOSC modes of operation.

Table 7-21. LFXOSC Modes of Operation

MODE

BP_C

PD_C

CLK_O

DESCRIPTION

ACTIVE

XTAL

CLK_OU

Active oscillator mode providing 32kHz

PWRDN

LOW

Output will be pulled down to LOW. PAD to be tri-stated. Active mode disabled

BYPASS

CLK

XI is driven by external clock source. XO is pulled down to LOW. Due to ESD

diode to supply, XI should not be driven unless oscillator supply is present.

Note

User should set CTRLMMR_WKUP_LFXOSC_TRIM[18:16] i_mult = 3b’001 for CL in the range 6pf to

9.5pf. CTRLMMR_WKUP_LFXOSC_TRIM [18:16] i_mult = 3b’010 for CL in the range 8.5pf to 12pf.

Default setting is 3b’010.

Note

The load capacitors, Cf1 and Cf2 in Figure 7-22, 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 WKUP_LFOSC0_XI, WKUP_LFOSC0_XO, and VSS pins.

AM625, AM623

SPRSP58A – JUNE 2022 – REVISED NOVEMBER 2022

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