MEMS Ultra-Low Power Oscillator, 32.768 kHz Quartz XTAL Replacement
IM890 Series
The IM890 is an ultra-small 32 kHz oscillator. In addition to
eliminating external output load capacitors common with
standard XTALs, this device includes special power supply
filtering and thus, eliminates the need for an external
Vdd bypass-decoupling capacitor. This feature further
simplifies the design and keeps the footprint as small as
possible. Internal power supply filtering is designed to reject
AC-noise greater than ±150 mVpp magnitude and
beyond 10 MHz frequency component.
Description
The 1.2V to 3.63V operating supply voltage range makes it an
ideal solution for mobile applications that incorporate
low-voltage, battery-back-up source such as a coin-cell or
super-cap.
a
XTAL Footprint Compatibility (SMD Package)
The IM890 is a replacement to the 32 kHz XTAL in the 2.0 x
1.2 mm (2012) package. Unlike XTAL resonators, The ILSI
silicon MEMS oscillators require a power supply (Vdd) and
ground (GND) pin. Vdd and GND pins are conveniently placed
between the two large XTAL pins. When using the ILSI
Solder Pad Layout (SPL), the IM890 footprint is compatible
with existing 32 kHz XTALs in the 2012 SMD package. Figure
2 shows the comparison between the quartz XTAL footprint
and the ILSI footprint.
Output Voltage
The IM890 has two output voltage options One option is a
standard LVCMOS output swing. The second option is the
NanoDrive reduced swing output. Output swing is customer
specific and programmed between 200 mV and 800 mV. For
DC-coupled applications, output V
VOL are individually
OH and
factory programmed to the customers’ requirement. VOH
programming range is between 600 mV and 1.225V in 100 mV
increments. Similarly, VOL programming range is between 350
mV and 800 mV. For example; a PMIC or MCU is internally
1.8V logic compatible, and requires a 1.2V VIH and a 0.6V VIL.
Simply select IM890 NanoDrive factory programming code to
be “D14” and the correct output thresholds will match the
downstream PMIC or MCU input requirements. Interface logic
will vary by manufacturer and we recommend that you review
the input voltage requirements for the input interface.
For DC-biased NanoDrive output configuration, the minimum
VOL is limited to 350mV and the maximum allowable swing
(VOH - VOL) is 750mV. For example, 1.1V VOH and 400mV
VOL is acceptable, but 1.2V VOH and 400 mV VOL is not
acceptable.
Figure 2 IM890 Footprint Compatibility with
Quartz Crystal Footprint
When the output is interfacing to an XTAL input that is inter-
nally AC-coupled, the IM890 output can be factory
programmed to match the input swing requirements. For
example, if a PMIC or MCU input is internally AC-coupled and
requires an 800mV swing, then simply choose the IM890
NanoDrive programming code “AA8” in the part number. It is
important to note that the IM890 does not include internal AC-
coupling capacitors. Please see the Part Number Ordering
section of the datasheet for more information about the part
number orderingscheme.
FrequencyStability
The IM890 is factory calibrated (trimmed) to guarantee
frequency stability to be less than 20 ppm at room
temperature and less than 100 ppm over the full -40°C to
+85°C temperature range. Unlike quartz crystals that have
a classic tuning fork parabola temperature curve with a
25°C turnover point, the IM890 temperature coefficient is
extremely flat across temperature. The device maintains
less than 100 ppm frequency stability over the full operating
temperature range when the operating voltage is
between 1.5 and 3.63V.
Power-up
The IM890 starts-up to a valid output frequency within
300 ms (150ms typ). To ensure the device starts-up within
the specified limit, make sure the power-supply ramps-up in
approximately 10 - 20 ms (to within 90% of Vdd). Start-up time
is measured from the time Vdd reaches 1.5V. For applications
that operate between 1.2V and 1.5V, the start-up time will be
longer.
Functionality is guaranteed over the 1.2V - 3.63V operating
supply voltage range. However, frequency stability
degrades below 1.5V and steadily degrades as it
approaches the 1.2V minimum supply due to the internal
regulator limitations. Between 1.2V and 1.5V, the frequency
stability is 250 ppm max over temperature.
When measuring the IM890 output frequency with
a
IM890 NanoDrive™
Figure 4 shows a typical IM890 output waveform (into a
10 pF load) when factory programmed for a 0.70V swing and
DC bias (VOH/VOL) for 1.8V logic:
frequency counter, it is important to make sure the
counter's gate time is >100ms. The slow frequency of a 32
kHz clock will give false readings with faster gatetimes.
Example:
Power Supply Noise Immunity
Rev 05/17/16_B
Page 4 of 10
ILSI America Phone 775-851-8880 ● Fax 775-851-8882 ●email: e-mail@ilsiamerica.com ●
www.ilsiamerica.com
Specifications subject to change without notice
Page 4 of 10
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