Datasheet

i.MX 6DualPlus/6QuadPlus Automotive Applications Processors, Rev. 3, 11/2018
38 NXP Semiconductors
Electrical Characteristics
from either a ~3 V backup battery (VDD_SNVS_IN) or VDD_HIGH_IN such as the oscillator consumes
power from VDD_HIGH_IN when that supply is available and transitions to the back up battery when
VDD_HIGH_IN is lost.
In addition, if the clock monitor determines that the OSC32K is not present, then the source of the 32 kHz
clock will automatically switch to the internal ring oscillator.
CAUTION
The internal RTC oscillator does not provide an accurate frequency and is
affected by process, voltage, and temperature variations. NXP strongly
recommends using an external crystal as the RTC_XTALI reference. If the
internal oscillator is used instead, careful consideration must be given to the
timing implications on all of the SoC modules dependent on this clock.
The OSC32k runs from VDD_SNVS_CAP, which comes from the VDD_HIGH_IN/VDD_SNVS_IN
power mux.
4.6 I/O DC Parameters
This section includes the DC parameters of the following I/O types:
• General Purpose I/O (GPIO)
• Double Data Rate I/O (DDR) for LPDDR2 and DDR3/DDR3L modes
•LVDS I/O
•MLB I/O
Table 20. OSC32K Main Characteristics
Parameter Min Typ Max Comments
Fosc — 32.768 kHz — This frequency is nominal and determined mainly by the crystal selected. 32.0 K
would work as well.
Current
consumption
—4 μA — The typical value shown is only for the oscillator, driven by an external crystal.
If the internal ring oscillator is used instead of an external crystal, then
approximately 25 μA must be added to this value.
Bias resistor — 14 MΩ — This the integrated bias resistor that sets the amplifier into a high gain state. Any
leakage through the ESD network, external board leakage, or even a scope probe
that is significant relative to this value will debias the amplifier. The debiasing will
result in low gain, and will impact the circuit's ability to start up and maintain
oscillations.
Target Crystal Properties
Cload — 10 pF — Usually crystals can be purchased tuned for different Cloads. This Cload value is
typically 1/2 of the capacitances realized on the PCB on either side of the quartz.
A higher Cload will decrease oscillation margin, but increases current oscillating
through the crystal.
ESR — 50 kΩ 100 kΩ Equivalent series resistance of the crystal. Choosing a crystal with a higher value
will decrease the oscillating margin.