ADIS16003
Accelerometer Conversion Details
Every time the accelerometer is sampled, the sampling function
discharges the internal C
X
or C
Y
filtering capacitors by up to 2%
of their initial values (assuming no additional external filtering
capacitors have been added). The recovery time for the filter
capacitor to recharge is approximately 10 渭s. Thus, sampling the
accelerometer at a rate of 10 kSPS or less does not induce a
sampling error. However, as sampling frequencies increase
above 10 kSPS, one can expect sampling errors to attenuate the
actual acceleration levels.
A conversion is initiated approximately every 350
渭s.
At this
time, the temperature sensor wakes up and performs a tempera-
ture conversion. This temperature conversion typically takes
25
渭s,
at which time the temperature sensor automatically shuts
down. The result of the most recent temperature conversion is
available in the serial output register at any time. Once the
conversion is finished, an internal oscillator starts counting and
is designed to time out every 350
渭s.
The temperature sensor
then powers up and does a conversion. Note that if the TCS is
brought low every 350
渭s
(鹵30%) or less, then the same
temperature value is output onto the DOUT line every time
without changing. It is recommended that the TCS line not be
brought low every 350
渭s
(鹵30%) or less. The 鹵30% covers
process variation. The TCS should become active (high to low)
outside this range.
The device is designed to auto convert every 350
渭s.
If the
temperature sensor is accessed during the conversion process,
an internal signal is generated to prevent any update of the
temperature value register during the conversion. This prevents
the user from reading back spurious data. The design of this
feature results in this internal lockout signal being reset only at
the start of the next auto conversion. Therefore, if the TCS line
goes active before the internal lockout signal is reset to its
inactive mode, the internal lockout signal is not reset. To ensure
that no lockout signal is set, bring TCS low at a greater time
than 350
渭s
(鹵30%). As a result, the temperature sensor is not
interrupted during a conversion process.
In the automatic conversion mode, every time a read or write
operation takes place, the internal clock oscillator is restarted at
the end of the read or write operation. The result of the conver-
sion is typically available 25
渭s
later. Reading from the device
before conversion is complete provides the same set of data.
Table 8. Temperature Sensor Data Format
Temperature
鈥?0擄C
鈥?5擄C
鈥?.25擄C
0擄C
+0.25擄C
+10擄C
+25擄C
+50擄C
+75擄C
+100擄C
+125擄C
Digital Output (DB9 鈥?DB0)
11 0110 0000
11 1001 1100
11 1111 1111
00 0000 0000
00 0000 0001
00 0010 1000
00 0110 0100
00 1100 1000
01 0010 1100
01 1001 0000
01 1111 0100
TEMPERATURE SENSOR SERIAL INTERFACE
Read Operation
Figure 4 shows the timing diagram for a serial read from the
temperature sensor. The TCS line enables the SCLK input. Ten
bits of data and a leading zero are transferred during a read
operation. Read operations occur during streams of 16 clock
pulses. The serial data is accessed in a number of bytes if 10 bits
of data are being read. At the end of the read operation, the
DOUT line remains in the state of the last bit of data clocked
out until TCS goes high, at which time the DOUT line from
the temperature sensor goes three-state.
Write Operation
Figure 4 also shows the timing diagram for the serial write
to the temperature sensor. The write operation takes place at
the same time as the read operation. Data is clocked into the
control register on the rising edge of SCLK. DIN should remain
low for the entire cycle.
Temperature Sensor Control Register
MSB
ZERO
ZERO
ZERO
ZERO
ZERO
ZERO
ZERO
LSB
ZERO
Table 7. Temperature Sensor Control Register Bit Functions
Bit
7 to 0
Mnemonic
ZERO
Comments
All bits should be held low.
ZERO
ZERO is defined as the logic low level.
Output Data Format
The output data format for the temperature sensor is twos
complement. Table 8 shows the relationship between the digital
output and the temperature.
Temperature Sensor Conversion Details
The ADIS16003 features a 10-bit digital temperature sensor
that allows an accurate measurement of the ambient device
temperature to be made.
The conversion clock for the temperature sensor is internally
generated so no external clock is required except when reading
from and writing to the serial port. In normal mode, an internal
clock oscillator runs the automatic conversion sequence.
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