nRF24LE1 Nordic VLSI, nRF24LE1 Datasheet - Page 118

• Manufacturer Part Number: nRF24LE1
• Manufacturer: Nordic VLSI

nRF24LE1 Preliminary Product Specification
C
C
the nRF24LE1 (typically 3pF when configured as crystal pins). C
as close as possible. The oscillator uses an amplitude regulated design similar to the 16MHz crystal oscil-
lator. For reliable operation the crystal load capacitance, shunt capacitance, equivalent series resistance
(ESR) and drive level must comply with the specifications in
use a crystal with lower than maximum ESR if the load capacitance and/or shunt capacitance is high. This
will give faster start-up and lower current consumption.
The start-up time is typically less than 0.5s for a crystal with 9pF load capacitance, 1pF shunt capacitance
and an ESR of 50k Ω . Bit 6 in the CLKLFCTRL register can be polled to check if the oscillator is ready for
use.
13.3.5
The low frequency clock may be generated by a 32kHz RC oscillator (RCOSC32K) instead of the crystal
oscillator, if a frequency accuracy of ± 10% is sufficient. This saves the cost of a crystal, and also frees up
P0.0 and P0.1 for other applications. The 32kHz RC oscillator is enabled by writing ‘001’ to CLKLFCTRL
2:0. It typically starts in less than 0.5ms. Bit 6 in the CLKLFCTRL register can be polled to check if the oscil-
lator is ready for use.
13.3.6
The low frequency clock can also be synthesized from the 16MHz crystal oscillator clock. Write ‘010’ to
CLKLFCTRL 2:0 to select this option. The synthesized clock will only be available in system modes where
the 16MHz crystal oscillator is active.
13.3.7
The nRF24LE1 may be used with an external 32kHz clock applied to the P0.1 port pin. Write ‘100’ to
CLKLFCTRL 2:0 if the external clock is a rail-to-rail digital signal, or ‘011’ if it is an analog signal coming
from e.g. the crystal oscillator of a microcontroller. An analog input signal must have an amplitude of 0.2V
peak-to-peak or higher. The DC level is not important as long as the applied signal never rises above VDD
or drops below VSS. The P0.1 port pin will load the microcontrollers crystal with approximately 3pF in addi-
tion to PCB routing.
Revision 1.1
1
PCB2
and C
are stray capacitances on the PCB, while C
2
are ceramic SMD capacitors connected between each crystal terminal and VSS, C
32kHz RC oscillator
Synthesized 32kHz clock
External 32kHz clock
118 of 191
PIN
is the input capacitance on the P0.0 and P0.1 pins of
Table 111. on page
1
and C
2
should be of the same value, or
177. It is recommended to
PCB1
and