LIS2L02AL Datasheet, PDF (10/17 Pages) STMicroelectronics – MEMS INERTIAL SENSOR: 2-axis - +/-2g ULTRACOMPACT LINEAR ACCELEROMETER

4 Application hints
4 Application hints
LIS2L02AL
Figure 3. LIS2L02AL Electrical Connection
Vdd
10µF 100nF
GND GND
ST
GND
LIS2L02AL
(top view)
Cload y
Cload x
Digital signals
Optional
Vout Y
X
1
Optional
Vout X
Y
DIRECTION OF THE
DETECTABLE
ACCELERATIONS
Power supply decoupling capacitors (100nF ceramic or polyester + 10µF Aluminum) should be
placed as near as possible to the device (common design practice).
The LIS2L02AL allows to band limit Voutx and Vouty through the use of external capacitors.
The re-commended frequency range spans from DC up to 2.0KHz. In particular, capacitors
must be added at output pins to implement low-pass filtering for antialiasing and noise
reduction. The equation for the cut-off frequency (f_t) of the external filters is:
f_t
=
----------------------------¹-----------------------------
2π ⋅ R_out ⋅ C_load(x, y)
Taking in account that the internal filtering resistor (R_out) has a nominal value equal to 110 kΩ,
the equation for the external filter cut-off frequency may be simplified as follows:
f_t = -_C----_l¹-_o---^.-_a⁴---_d-⁵--₍-^µ--_x--^F_,----_y---₎-[Hz]
The tolerance of the internal resistor can vary typically of ±20% within its nominal value of
110kΩ; thus the cut-off frequency will vary accordingly. A minimum capacitance of 723 pF for
C_load(x, y) is required in any case.
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