DA6505.005
11 June 2018
FUNCTIONAL DESCRIPTION (continued)
Operating modes
Only two registers are needed for configuring and
running the measurements. The Configuration
register (EE/6EHEX) contains only measurement
configuration settings. See table 3. The Control
register (EF/6FHEX) contains measurement and
operating mode selection settings. Writing to Control
register starts the selected measurements. See table
4.
Selected measurements are performed during the
measurement period. To minimize current
consumption the device enters standby mode for the
time between measurements during which only the
internal clock oscillator is running. The standby
mode time is defined by a DELAY bit setting in the
Configuration register (EE/6EHEX). There are eight
delay settings available; 0.5ms, 62.5ms, 125ms,
250ms, 500ms, 1000ms, 2000ms and 4000ms. The
normal mode measurement cycle is a sum of
selected measurements’ A/D conversion time and
the delay setting. See figure 2 for normal mode
measurement cycle illustration. The normal mode is
recommended in applications where IIR filter is used
like for filtering short-term sensor signal
disturbances.
MAS6505 has three selectable operating modes;
sleep mode, forced mode (single command based
measurement) and normal mode (automated
measurements). The operating mode is selected by
MODE bits in the Control register (EF/6FHEX).
In the sleep mode (MODE=00) the device does not
perform any measurements and only a very small
sleep current is drawn from the supplies.
Selection
of
temperature
and
pressure
In the forced mode (MODE=01, 10) selected
measurements are run only once after which the
device returns automatically to the sleep mode.
Every new measurement requires writing a new
forced mode command into the Control register. In
the forced mode an internal clock oscillator is turned
on only during the measurement. The forced mode
is recommended in applications that use low
measurement rate or require host based
synchronization of measurements.
measurements and their resolution can be done
independently using OSRT and OSRP oversampling
ratio settings in the Control register (EF/6FHEX). Each
oversampling ratio has seven settings 1/4x, 1/2x, 1x,
2x, 4x, 8x and 16x in addition to no measurement
setting. The highest value setting gives highest
resolution but it has the longest A/D conversion time
and the highest power consumption. Similar way the
lowest value setting gives the lowest resolution but it
has the shortest A/D conversion time and the lowest
power consumption. Thus the multiple oversampling
ratio settings allow optimizing measurements
between speed, power consumption and resolution.
See ELECTRICAL CHARACTERISTICS on pages
3-7.
In the normal mode (MODE=11) selected
measurements are performed automatically in a loop
at a selected rate until the sleep mode (MODE=00)
is selected. Normal mode measurement cycle
comprises of a measurement and a standby period.
Digital IIR low pass filter
The Configuration register (EE/6EHEX
)
has
applied to both temperature and pressure signals.
The filtered temperature and pressure conversion
results are stored into the Temperature result
registers (F4/74…F6/76HEX) and the Pressure result
registers (F1/71…F3/73HEX) respectively. The IIR
filter can be applied to both forced and normal
modes.
additionally selection for a digital infinite impulse
response (IIR) type low pass filter option with four
different filter coefficients 2, 4, 8 and 16. See table 3.
The IIR low pass filter can be used to damp sudden
variations in the sensor signal and to further improve
noise resolution by an additional filtering of the noise.
The filter does not affect output data rate but step
response delay. When selected the filtering is
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MAS [ MICRO ANALOG SYSTEMS ]
