NXP Semiconductors KL25 Series - External Crystal; Resonator Connections

Table 25-1. OSC Signal Descriptions
Signal Description I/O
EXTAL External clock/Oscillator input I
XTAL Oscillator output O
25.5 External Crystal / Resonator Connections
The connections for a crystal/resonator frequency reference are shown in the following
figures. When using low-frequency, low-power mode, the only external component is the
crystal or ceramic resonator itself. In the other oscillator modes, load capacitors (C
x
, C
y
)
and feedback resistor (R
F
) are required. The following table shows all possible
connections.
Table 25-2. External Caystal/Resonator Connections
Oscillator Mode Connections
Low-frequency (32 kHz), low-power Connection 1
1
Low-frequency (32 kHz), high-gain Connection 2/Connection 3
2
High-frequency (3~32 MHz), low-power Connection 3
1
High-frequency (3~32 MHz), high-gain Connection 3
1. With the low-power mode, the oscillator has the internal feedback resistor R
F
. Therefore, the feedback resistor must not be
externally with the Connection 3.
2. When the load capacitors (Cx, Cy) are greater than 30 pF, use Connection 3.
OSC
EXTAL
Crystal or Resonator
V
SS
XTAL
Figure 25-2. Crystal/Ceramic Resonator Connections - Connection 1
Chapter 25 Oscillator (OSC)
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 407