EVAL-ADM1063TQEBZ Analog Devices Inc, EVAL-ADM1063TQEBZ Datasheet - Page 21

• Manufacturer Part Number: EVAL-ADM1063TQEBZ
• Description: BOARD EVALUATION FOR ADM1063TQ
• Manufacturer: Analog Devices Inc

Specifications of EVAL-ADM1063TQEBZ

• Main Purpose: Power Management, Power Supply Supervisor/Tracker/Sequencer
• Embedded: No
• Utilized Ic / Part: ADM1063
• Primary Attributes: 10 Channel Supervisor / Sequencer, 6 Voltage Output DACs
• Secondary Attributes: GUI Programmable via SMBus (via USB)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TEMPERATURE MEASUREMENT SYSTEM
The ADM1063 contains an on-chip, band gap temperature
sensor, whose output is digitized by the on-chip, 12-bit ADC.
Theoretically, the temperature sensor and the ADC can measure
temperatures from −128°C to +128°C with a resolution of 0.125°C.
Because this exceeds the operating temperature range of the device,
local temperature measurements outside this range are not possible.
Temperature measurements from −128°C to +128°C are possible
using a remote sensor. The output code is in offset binary format,
with −128°C given by Code 0x400, 0°C given by Code 0x800,
and +128°C given by Code 0xC00.
As with the other analog inputs to the ADC, a limit register is
provided for each of the temperature input channels. Therefore,
a temperature limit can be set such that if it is exceeded, a warning
is generated and available as an input to the sequencing engine.
This enables users to control their sequence or monitor functions
based on an overtemperature or undertemperature event.
REMOTE TEMPERATURE MEASUREMENT
The ADM1063 can measure the temperature of two remote
diode sensors or diode-connected transistors connected to the
DxN and DxP pins.
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, the absolute value
of V
is required to null it, making the technique unsuitable for mass
production. The technique used in the ADM1063 is to measure
the change in V
currents.
The change in V
where:
k is Boltzmann’s constant.
q is the charge on the carrier.
T is the absolute temperature in Kelvin.
N is the ratio of the two currents.
BE
ΔV
varies from device to device, and individual calibration
BE
= kT/q × ln(N)
BE
BE
when the device is operated at two different
is given by
TRANSISTOR
SENSING
REMOTE
CPU
Figure 31. Signal Conditioning for Remote Diode Temperature Sensors
THERM DA
THERM DC
DxP
DxN
I
DIODE
BIAS
Rev. B | Page 21 of 32
N × I
I
BIAS
LOW-PASS FILTER
f
V
C
DD
= 65kHz
Figure 31 shows the input signal conditioning used to measure the
output of a remote temperature sensor. This figure shows the
external sensor as a substrate transistor provided for temperature
monitoring on some microprocessors, but it could equally be
a discrete transistor such as a 2N3904 or 2N3906.
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 DxN input and the emitter is connected to the
DxP input. If an NPN transistor is used, the emitter is connected
to the DxN input and the base is connected to the DxP input.
Figure 29 and Figure 30 show how to connect the ADM1063
to an NPN or PNP transistor for temperature measurement.
To prevent ground noise from interfering with the measurement,
the more negative terminal of the sensor is not referenced to
ground but is biased above ground by an internal diode at the
DxN input.
Figure 29. Measuring Temperature Using an NPN Transistor
Figure 30. Measuring Temperature Using a PNP Transistor
2N3904
2N3906
NPN
PNP
V
V
OUT+
OUT–
DxP
DxN
DxP
DxN
ADM1063
ADM1063
TO ADC
ADM1063