ADT7516ARQ Analog Devices Inc, ADT7516ARQ Datasheet - Page 26

• Manufacturer Part Number: ADT7516ARQ
• Description: DTS,12-Bit Quad DAC,4 Analog Inputs I.C.
• Manufacturer: Analog Devices Inc

Specifications of ADT7516ARQ

• 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
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With: EVAL-ADT7516EBZ - BOARD EVALUATION FOR ADT7516
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

ADT7516/ADT7517/ADT7519
Table 8. V
V
2.7
3
3.5
4
4.5
5
5.5
6
6.5
7
On-Chip Reference
The ADT7516/ADT7517/ADT7519 have an on-chip 1.2 V band
gap reference that is gained up by a switched capacitor amplifier
to give an output of 2.28 V. The amplifier is powered up for the
duration of the device monitoring phase and is powered down
once monitoring is disabled. This saves on current consumption.
The internal reference is used as the reference for the ADC. The
ADC is used for measuring V
external temperature sensor, and AIN inputs. The internal
reference is always used when measuring V
and external temperature sensors. The external reference is the
default power-up reference for the DACs.
Round Robin Measurement
On power-up, the ADT7516/ADT7517/ADT7519 go into round
robin mode, but monitoring is disabled. Setting Bit C0 of the
Control Configuration 1 register to 1 enables conversions. It
sequences through all the available channels, taking a
measurement from each in the following order: V
temperature sensor, external temperature sensor (AIN1 and
AIN2), AIN3, and AIN4. Pin 7 and Pin 8 can be configured to
be either external temperature sensor pins or standalone analog
input pins. Once conversion is completed on the AIN4 channel,
the device loops around for another measurement cycle. This
method of taking a measurement on all the channels in one
cycle is called round robin. Setting Bit C4 of Control
Configuration 2 (Address 0x19) disables the round robin mode
and in turn sets up the single-channel mode. In single-channel
mode, only one channel (for example, the internal temperature
sensor) is measured in each conversion cycle.
The time taken to monitor all channels is normally not of
interest, because the most recently measured value can be read
at any time. For applications where the round robin time is
important, typical times at 25°C are given in the Specifications
section.
Single Channel Measurement
Setting C4 of the Control Configuration 2 register enables the
single channel mode and allows the ADT7516/ADT7517/
ADT7519 to focus on one channel only. A channel is selected by
DD
Value (V)
DD
Data Format (V
Binary
01 1000 1011
01 1011 0111
10 0000 0000
10 0100 1001
10 1001 0010
10 1101 1100
11 0010 0101
11 0110 1110
11 1011 0111
11 1111 1111
DD
REF
, internal temperature sensor,
= 2.28 V)
Digital Output
DD
, and the internal
DD
, internal
Hex
18B
1B7
200
249
292
2DC
325
36E
3B7
3FF
Rev. B | Page 26 of 44
writing to Bits[C0:C2] in the Control Configuration 2 register.
For example, to select the V
the Control Configuration 2 register and set C4 to 1 (if not done
so already), then write all 0s to Bits[C0:C2]. All subsequent
conversions are done on the V
channel selection to the internal temperature channel, write to
the Control Configuration 2 register and set C0 = 1. When
measuring in single channel mode, conversions on the channel
selected occur directly after each other. Any communication to
the ADT7516/ADT7517/ADT7519 stops the conversions, but
they are restarted once the read or write operation is completed.
Temperature Measurement Method
Internal Temperature Measurement
The ADT7516/ADT7517/ADT7519 contain an on-chip band
gap temperature sensor whose output is digitized by the on-chip
ADC. The temperature data is stored in the internal temperature
value register. Because both positive and negative temperatures
can be measured, the temperature data is stored in twos comple-
ment format, as shown in Table 9. The thermal characteristics
of the measurement sensor can change and, therefore, an offset
is added to the measured value to enable the transfer function
to match the thermal characteristics. This offset is added before
the temperature data is stored. The offset value used is stored in
the internal temperature offset register.
External Temperature Measurement
The ADT7516/ADT7517/ADT7519 can measure the temperature
of one external diode sensor or diode-connected transistor.
The forward voltage of a diode or diode connected transistor,
operated at a constant current, exhibits a negative temperature
coefficient of about −2 mV/°C. Unfortunately, because the
absolute value of V
individual calibration is required to null this out, the technique
is unsuitable for mass production.
The technique used in the ADT7516/ADT7517/ADT7519 is to
measure the change in V
different currents. This is given by
where:
k is Boltzmann’s constant.
q is the charge on the carrier.
T is the absolute temperature in kelvins.
N is the ratio of the two currents.
Figure 45 shows the input signal conditioning used to measure
the output of an external temperature sensor. This figure shows
the external sensor as a substrate transistor, provided for
temperature monitoring on some microprocessors, but it can
equally well be a discrete transistor.
If a discrete transistor is used, the collector is not grounded, and
should be linked to the base. If a PNP transistor is used, the
base is connected to the D− input and the emitter to the D+
ΔV
BE
= kT/q × ln(N)
BE
varies from device to device, and
BE
when the device is operated at two
DD
channel for monitoring, write to
DD
channel only. To change the