AD7416/AD7417/AD7418
Rev. I | Page 19 of 24
APPLICATIONS INFORMATION
SUPPLY DECOUPLING
The AD7416/AD7417/AD7418 should be decoupled with a
0.1 μF ceramic capacitor between V
DD
and GND. This is
particularly important if the part is mounted remote from the
power supply.
POWER-ON RESET
To ensure proper power-on reset, make sure that the supply
voltage on the V
DD
pin is at 0 V. Refer to the AN-588 Application
Note, AD7416/AD7417/AD7418 Power-On Reset Circuit at
www.analog.com for more information. A failed power-on reset
can prevent the default values from being loaded into the AD7416/
AD7417/AD7418 registers. If the correct values are not loaded
into the registers, then the device cannot start operating. The
output from the temperature value and ADC value registers will
be a constant value.
To restart the device operation, the registers have to be loaded
with their default values via the I
2
C bus. Therefore, in the event
of an inadequate power-on reset and for all three devices, the
following registers should be loaded with their default values:
• Configuration register—default value = 0x00
• Config2 register—default value = 0x00
• T
HYST
setpoint register—default value = 0x4B00
• T
OTI
setpoint register—default value = 0x5500
MOUNTING THE AD7416/AD7417/AD7418
The AD7416/AD7417/AD7418 can be used for surface or air
temperature sensing applications. If the device is cemented to a
surface with thermally conductive adhesive, the die temperature
is within about 0.2°C of the surface temperature, due to the low
power consumption of the device. Take care to insulate the back
and leads of the device from the air if the ambient air
temperature is different from the surface temperature being
measured.
The GND pin provides the best thermal path to the die, so the
temperature of the die is close to that of the printed circuit
ground track. Take care to ensure that this is in close thermal
contact with the surface being measured.
As with any IC, the AD7416/AD7417/AD7418 and its associated
wiring and circuits must be kept free from moisture to prevent
leakage and corrosion, particularly in cold conditions where
condensation is more likely to occur. Water resistant varnishes
and conformal coatings can be used for protection. The small
size of the AD7416 package allows it to be mounted inside sealed
metal probes that provide a safe environment for the device.
FAN CONTROLLER
Figure 23 shows a simple fan controller that switches on a
cooling fan when the temperature exceeds 80°C and switches it
off again when the temperature falls below 75°C. The AD7416
can be used as a standalone device in this application or with a
serial bus interface if different trip temperatures are required. If the
AD7416 is used with a bus interface, the sense of OTI can be set
to active high, Q1 and R1 can be omitted, and OTI can be con-
nected directly to the gate of Q2, with R2 as the pull-up resistor.
8
4
3
V
DD
3V TO 5.5V
12
AD7416
R1
10kΩ
R2
10kΩ
Q1
2N3904
OR SIMILAR
Q2
LOGIC LEVEL
MOSFET RATED
TO SUIT FAN
CURRENT
01126-020
Figure 23. AD7416 Used as a Fan Controller
THERMOSTAT
Figure 24 shows the AD7416 used as a thermostat. The heater
switches on when the temperature falls below T
HYST
and
switches off again when the temperature rises above T
OTI
. For
this application and for comparator mode, program the OTI
output active low.
8
4
3
V
DD
3V TO 5.5V
AD7416
R1
10kΩ
RELAY
Q1
2N3904
OR SIMILAR
D1
1N4001
HEATER
SUPLY
RLA1
HEATER
01126-021
Figure 24. AD7416 Used as a Thermostat
