MAS6505 datasheet(9/44 Pages) MAS

9 / 44 page

DA6505.005

11 June 2018

9 (44)

FUNCTIONAL DESCRIPTION (continued)

 Operating modes

Only two registers are needed for configuring and

running

the

measurements.

The

Configuration

configuration settings. See table 3. The Control

operating mode selection settings. Writing to Control

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.

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

require

host

based

synchronization of measurements.

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.

Selected measurements are performed during the

measurement

period.

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

for

filtering

short-term

sensor

signal

disturbances.

Selection

temperature

and

pressure

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.

 Digital IIR low pass filter

The

Configuration

(EE/6EHEX)

has

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

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.

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