Specifications

WM_PRJ_Q2501_PTS_002 - 001
March 2004
confidential ©
Page: 51 / 79
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Note that a 1.8 V/ 5 V voltage level adaptation is implemented between the
WISMO Q2501 signals and the sensor devices (A/D converter and temperature
sensor). Voltage level adaptation is implemented using open-drain buffers and
pull-up resistors connected to the open-drain outputs.
The 100 kΩ resistor connected between PCS1_N signal and VDD18_OUT is
required to keep PCS1_N high (inactive) during power up when PCS1_N is
temporarily in high impedance state.
To get better results, it is recommended to filter (low pass filter) a dedicated
5 Volt voltage used to:
 supply the gyroscope,
 provide the reference voltage to the A/D converter (VREF input).
Even smallest voltage drops on the 5 V supply (due to load changes in the
WISMO Q2501 module) can have a negative impact on the DR accuracy in
case of prolonged outages (i.e. long tunnels).
Appropriate coupling capacitors must be added as well according to the
recommendations given in the data sheets of the illustrated semiconductor
devices.
All the resistors used will have 5 % accuracy or better. In the same way
capacitors (X7R type) will have 10 % accuracy or better.
Notes
:
 for correct operation with the GPS EKF (Enhanced Kalman Filters)
firmware provided, the diagram given in Figure 32 must be adopted
without making any modifications like (but not limited to) using different
types of semiconductor devices and changing signal assignment.
 The following gyroscopes have been approved, so do not use any
others:
 MURATA:
 ENV-05F,
 ENV-05G,
 PANASONIC :
 EWTS82.
 Please follow the design recommendations from gyroscope
manufacturers for proper analog signal conditioning.