EVAL-AD7416/7/8EB Analog Devices Inc, EVAL-AD7416/7/8EB Datasheet - Page 18

• Manufacturer Part Number: EVAL-AD7416/7/8EB
• Description: BOARD EVALUATION FOR AD7416/7/8
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD7416/7/8EB

• Sensor Type: Temperature
• Sensing Range: -40°C ~ 125°C
• Interface: I²C
• Voltage - Supply: 2.7 V ~ 5.5 V
• Embedded: No
• Utilized Ic / Part: AD7416, AD7417, AD7418
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD7416/AD7417/AD7418
Mode 2
For applications where temperature measurements are required
at a slower rate, for example, every second, power consumption
of the part can be reduced by writing to the part to go to a full
power-down between reads. The current consumption in full
power-down is typically 0.2 μA and full power-down is initiated
when D0 = 1 in the configuration register. When a measurement is
required, a write operation can be performed to power up the
part. The part then performs a conversion and is returned to
power-down. The temperature value can be read in full power-
down because the I
The power dissipation in this mode depends on the rate at which
reads take place. Taking the requirements for a temperature
measurement every 100 ms as an example, the optimum power
dissipation is achieved by placing the part in full power-down,
waking it up every 100 ms, letting it operate for 400 μs and
putting it into full power-down again. In this case, the average
power consumption is calculated as follows. The part spends
40 μs (or 0.04% of time) converting with 3 mW dissipation
and a 99.96 ms (99.96% of time) in full shutdown with 60 nW
dissipation.
Thus, the average power dissipation is
The fastest throughput rate at which the AD7416/AD7417/
AD7418 can be operated is 2.5 kHz (that is, a read every 400 μs
conversion period). Because T
read time with the I
temperature reads are called too often, reads will overlap with
conversions, aborting them continuously, which results in
invalid readings.
CONVST START MODE
The AD7417/AD7418 have an extra mode, set by writing to the
MSB of the Config2 register.
3 mW × 0.004 + 60 nW × 0.9996 = 1.2 μW
2
2
C operating at 100 kbps would be 270 μs. If
C bus is continuously active.
OTI
and T
HYST
are 2-byte reads, the
Rev. I | Page 18 of 24
CONVST Pin Mode
Conversions are initiated only by using the CONVST pin. In
this method of operation, CONVST is normally low.
The rising edge of CONVST starts the power-up time. This
power-up time is 4 μs. If the CONVST high time is longer than
4 μs, a conversion is initiated on the falling edge of CONVST
and the track-and-hold also enters its hold mode at this time.
If the CONVST high time is less than 4 μs, an internal timer,
initiated by the rising edge of CONVST , holds off the track-
and-hold and the initiation of conversion until the timer times
out (4 μs after the rising edge of CONVST , which corresponds
with the power-up time). The CONVST input remains low at
the end of conversion, thus causing the part to enter its power-
down mode. In this method of operation, CONVST is normally
low with a high going pulse controlling the power-up, and the
conversion starts.
The CONVST pin should not be pulsed when reading from or
writing to the port.
Figure 21 shows the recommended minimum times for the
CONVST pulse when the temperature channel is selected.
Figure 22
selected.
CONVST
CONVST
Figure 21. CONVST When Temperature Channel Selected
shows the minimum times an analog input channel is
Figure 22. CONVST When V
100ns
100ns
15µs
40µs
IN
Channel Selected