AM4376 datasheet(131/261 Pages) TI

131 / 261 page

Device

XTALIN

VSS_OSC

XTALOUT

Optional R

Crystal

Optional R

bias

AM4376, AM4377, AM4378, AM4379

www.ti.com

SPRS851B – JUNE 2014 – REVISED APRIL 2015

5.12.2.3 Input Clock Requirements

5.12.2.3.1 OSC0 Internal Oscillator Clock Source

Figure 5-10 shows the recommended crystal circuit. It is recommended that pre-production 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 pre-production PCBs.

The XTALIN terminal has a 15 - 40 k

Ω internal pulldown resistor which is enabled when OSC0 is disabled. This

internal resistor prevents the XTALIN terminal from floating to an invalid logic level which may increase leakage

current through the oscillator input buffer.

Oscillator components (Crystal, C1, C2, optional Rbias and Rd) must be located close to the package. Parasitic

capacitance to the printed circuit board (PCB) ground and other signals should be minimized to reduce noise coupled

into the oscillator. The external crystal component grounds should be connected to the VSS_OSC terminal. The

VSS_OSC terminal should be connected to the PCB ground plane as close as possible to the device.

C1 and C2 represent the total capacitance of the respective PCB trace, load capacitor, and other components

(excluding the crystal) connected to each crystal terminal. The value of capacitors C1 and C2 should be selected to

provide the total load capacitance, CL, specified by the crystal manufacturer. The total load capacitance is CL =

[(C1*C2)/(C1+C2)] + Cshunt, where Cshunt is the crystal shunt capacitance (C0) specified by the crystal manufacturer

plus any mutual capacitance (Cpkg + CPCB) seen across the XTALIN and XTALOUT signals. For recommended values

of crystal circuit components, see Table 5-13.

Figure 5-10. OSC0 Crystal Circuit Schematic

Specifications

131

Submit Documentation Feedback

Product Folder Links: AM4376 AM4377 AM4378 AM4379

AM4376 Datasheet(PDF) 131 Page - Texas Instruments