ADT7518ARQ-REEL Analog Devices Inc, ADT7518ARQ-REEL Datasheet - Page 19

• Manufacturer Part Number: ADT7518ARQ-REEL
• Description: IC SENSOR TEMP W/ADC/DAC 16QSOP
• Manufacturer: Analog Devices Inc

Specifications of ADT7518ARQ-REEL

• Rohs Status: RoHS non-compliant
• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 120°C, External Sensor
• Output Type: I²C™, MICROWIRE™, QSPI™, SPI™
• Output Alarm: No
• Output Fan: No
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP

DAC Reference Inputs
There is an input reference pin for the DACs. This reference
input is buffered (see Figure 40).
The advantage with the buffered input is the high impedance it
presents to the voltage source driving it. The user can have an
external reference voltage as low as 1 V and as high as V
restriction of 1 V is due to the footroom of the reference buffer.
The LDAC configuration register controls the option to select
between internal and external voltage references. The default
setting is for external reference selected.
Output Amplifier
The output buffer amplifier can generate output voltages to
within 1 mV of either rail. Its actual range depends on the value
of V
If a gain of 1 is selected (Bits 0 to 3 of the DAC configuration
register = 0), the output range is 0.001 V to V
If a gain of 2 is selected (Bits 0 to 3 of the DAC configuration
register = 1), the output range is 0.001 V to 2 V
clamping, however, the maximum output is limited to V
0.001 V.
The output amplifier can drive a load of 4.7 kΩ to GND or V
in parallel with 200 pF to GND or V
source and sink capabilities of the output amplifier can be seen
in the plot of Figure 16.
The slew rate is 0.7 V/µs with a half-scale settling time to
±0.5 LSB (at 8 bits) of 6 µs.
Thermal Voltage Output
The ADT7518 can output voltages that are proportional to
temperature. DAC A output can be configured to represent the
temperature of the internal sensor while DAC B output can be
configured to represent the external temperature sensor. Bits C5
and C6 of the Control Configuration 3 register select the temp-
erature proportional output voltage. Each time a temperature
measurement is taken, the DAC output is updated. The output
resolution for the ADT7518 is 8 bits with a 1°C change corres-
ponding to 1 LSB change. The default output range is 0 V to
REF
, gain, and offset error.
OPTIONAL CAPACITOR, UP TO
3nF MAX. CAN BE ADDED TO
IMPROVE HIGH FREQUENCY
NOISE REJECTION IN NOISY
ENVIRONMENTS
TRANSISTOR
SENSING
REMOTE
(2N3906)
DD
(see Figure 5). The
Figure 41. Signal Conditioning for External Diode Temperature Sensor
REF
REF
.
. Because of
D+
C1
D–
LOW-PASS
f
DD
C
DD
FILTER
= 65kHz
. The
−
Rev. A | Page 19 of 40
DD
,
I
DIODE
BIAS
N × I
V
output voltage span to 2 V
DAC A (internal temperature sensor) and D1 = 1 for DAC B
(external temperature sensor) in the DAC configuration register
(Address 1Bh).
The output voltage is capable of tracking a maximum temp-
erature range of –128°C to +127°C, but the default setting is
–40°C to +127°C. If the output voltage range is 0 V to V
(V
–40°C, and 1.48 V representing +127°C. This, of course, will
give an upper deadband between 1.48 V and V
The internal and external analog temperature offset registers
can be used to vary this upper deadband and, consequently, the
temperature that 0 V corresponds to. Table 6 and Table 7 give
examples of how this is done using a DAC output voltage span
of V
value, in twos complement format, at which 0 V is to start. For
example, if using the DAC A output and 0 V to start at –40°C,
program D8h into the internal analog temperature offset reg-
ister (Address 21h). This is an 8-bit register and has a temp-
erature offset resolution of only 1°C for all device models. Use
the formulas following the tables to determine the value to
program into the offset registers.
Table 6. Thermal Voltage Output (0 V to V
O/P Voltage (V)
0
0.5
1
1.12
1.47
1.5
2
2.25
∗ Upper deadband has been reached. DAC output is not capable of
I
increasing. See Fig
BIAS
REF
REF
REF
and this can be increased to 0 V to 2 V
-IN = 2.25 V), then this corresponds to 0 V representing
and 2 V
V
DD
REF
ure 9
, respectively. Simply write in the temperature
Default °C
–40
+17
+73
+87
+127
UDB
UDB∗
UDB∗
.
∗
REF
TO ADC
V
V
OUT+
OUT–
can be done by setting D0 = 1 for
Max °C
–128
–71
–15
–1
+39
+42
+99
+127
REF
REF
. Increasing the
REF
)
.
ADT7518
Sample °C
0
+56
+113
+127
UDB∗
UDB∗
UDB∗
UDB∗
REF
-IN