FS32K148UFT0VLHT datasheet(38/100 Pages) NXP

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Table 27. External System Oscillator electrical specifications

(continued)

Symbol

Description

Min.

Typ.

Max.

Unit

Notes

High-gain mode (HGO=1)

—

MΩ

RS, 3

Series resistor

Low-gain mode (HGO=0)

—

kΩ

High-gain mode (HGO=1)

—

kΩ

Vpp_XTAL Peak-to-peak amplitude of oscillation (oscillator mode) at XTAL

Low-gain mode (HGO=0)

—

1.0

—

High-gain mode (HGO=1)

—

3.3

—

Vpp_EXTAL Peak-to-peak amplitude of oscillation (oscillator mode) at EXTAL

4, 5

Low-gain mode (HGO=0)

0.8

—

High-gain mode (HGO=1), VDD= 4.0 V to 5.5 V

1.7

—

VSOSCOP Oscillation operating point

High-gain mode (HGO=1)

1.15

—

1. Crystal oscillator circuit provides stable oscillations when gmXOSC > 5 * gm_crit. The gm_crit is defined as:

gm_crit = 4 * (ESR + RS) * (2πF)2 * (C0 + CL)2

where:

• gmXOSC is the transconductance of the internal oscillator circuit

• ESR is the equivalent series resistance of the external crystal

• RS is the series resistance connected between XTAL pin and external crystal for current limitation

• F is the external crystal oscillation frequency

• C0 is the shunt capacitance of the external crystal

• CL is the external crystal total load capacitance. CL = Cs+ [C1*C2/(C1+C2)]

• Cs is stray or parasitic capacitance on the pin due to any PCB traces

• C1, C2 external load capacitances on EXTAL and XTAL pins

See manufacture datasheet for external crystal component values

• When low-gain is selected, internal RF will be selected and external RF should not be attached.

• When high-gain is selected, external RF (1 M Ohm) needs to be connected for proper operation of the crystal. For

external resistor, up to 5% tolerance is allowed.

3. RS should be selected carefully to have appropriate oscillation amplitude for both protecting crystal or resonator device and

satisfying proper oscillation startup condition.

4. The EXTAL and XTAL pins should only be connected to required oscillator components and must not be connected to any

other devices.

5. Minimum value is shown as a reference only, however the HW design needs to ensure it reaches the maximum value by

following the guidelines given in above notes (notes 1, 2, and 3) and performs the required robustness testing at the

application level. During testing, a low capacitance probe (< 5 pF ) must be used to avoid any decrease in the Vpp_EXTAL

value.

6.2.2 External System Oscillator frequency specifications

Clock interface modules

S32K1xx Data Sheet, Rev. 13, 04/2020

NXP Semiconductors

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