EVAL-ADT7467EBZ ON Semiconductor, EVAL-ADT7467EBZ Datasheet - Page 15

• Manufacturer Part Number: EVAL-ADT7467EBZ
• Description: BOARD EVALUATION FOR ADT7467
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of EVAL-ADT7467EBZ

• Sensor Type: Temperature
• Sensing Range: -40°C ~ 120°C
• Interface: SMBus (2-Wire/I²C)
• Sensitivity: ±1.5°C
• Voltage - Supply: 3 V ~ 5.5 V
• Embedded: No
• Utilized Ic / Part: ADT7467
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ANALOG-TO-DIGITAL CONVERTER
All analog inputs are multiplexed into the on-chip, successive
approximation, analog-to-digital converter, which has a resolu-
tion of 10 bits. The basic input range is 0 V to 2.25 V, but the
input has built-in attenuators to allow measurement of V
without any external components. To allow for the tolerance of
the supply voltage, the ADC produces an output of 3/4 full scale
(decimal 768 or 300 hexadecimal) for the nominal input voltage
and, therefore, has adequate headroom to deal with
overvoltages.
VOLTAGE MEASUREMENT INPUT
The ADT7467 has one external voltage measurement channel.
It can also measure its own supply voltage, V
measure V
out through the V
Register 1 (0x40) allows a 5 V supply to power the ADT7467
and be measured without overranging the V
channel. The V
voltage in computer systems.
Input Circuitry
The internal structure for the V
Figure 22. The input circuit consists of an input protection
diode, an attenuator, and a capacitor to form a first-order low-
pass filter that gives the input immunity to high frequency noise.
Voltage Measurement Registers
Register 0x21 V
Register 0x22 V
V
Associated with the V
high and low limit register. Exceeding the programmed high or
low limit causes the appropriate status bit to be set. Exceeding
either limit can also generate SMBALERT interrupts.
Register 0x46 V
Register 0x47 V
Register 0x48 V
Register 0x49 V
Table 6
codes of the 10-bit ADC.
CCP
Limit Registers
shows the input ranges of the analog inputs and output
CCP
. The V
V
CCP
CCP
CCP
CC
CCP
CCP
CC
CC
Figure 22. Structure of Analog Inputs
CC
reading = 0x00 default
low limit = 0x00 default
high limit = 0xFF default
input can be used to monitor a chipset supply
reading = 0x00 default
low limit = 0x00 default
high limit = 0xFF default
pin (Pin 3). Setting Bit 7 of Configuration
CC
CCP
supply voltage measurement is carried
17.5kΩ
and V
52.5kΩ
CC
CCP
measurement channels is a
analog input is shown in
35pF
CC
CC
. Pin 14 can
measurement
Rev. 3 | Page 15 of 77 | www.onsemi.com
CCP
When the ADC is running, it samples and converts a voltage
input in 0.7 ms and averages 16 conversions to reduce noise; a
measurement takes nominally 11 ms.
ADDITIONAL ADC FUNCTIONS
FOR VOLTAGE MEASUREMENTS
A number of other functions are available on the ADT7467 to
offer the system designer increased flexibility.
Turn-Off Averaging
For each voltage measurement read from a value register,
16 readings are made internally, the results of which are averaged
and then placed into the value register. For instances where faster
conversions are needed, setting Bit 4 of Configuration Register 2
(0x73) turns averaging off. This produces a reading that is 16
times faster (0.7 ms), but the reading may be noisier.
Bypass Voltage Input Attenuator
Setting Bit 5 of Configuration Register 2 (0x73) removes the
attenuation circuitry from the V
to directly connect external sensors or to rescale the analog
voltage measurement inputs for other applications. The input
range of the ADC without the attenuators is 0 V to 2.25 V.
Single-Channel ADC Conversion
Setting Bit 6 of Configuration Register 2 (0x73) places the
ADT7467 into single-channel ADC conversion mode. In this
mode, the ADT7467 can be made to read a single voltage
channel only. If the internal ADT7467 clock is used, the selected
input is read every 0.7 ms. The appropriate ADC channel is
selected by writing to Bits <7:5> of the TACH1 minimum high
byte register (0x55).
Table 5. Programming Single-Channel ADC Mode
Bits <7:5>, Register 0x55
001
010
101
110
111
Configuration Register 2 (0x73)
<4> = 1, averaging off
<5> = 1, bypass input attenuators
<6> = 1, single-channel conversion mode
TACH1 Minimum High Byte (0x55)
<7:5> selects ADC channel for single-channel convert mode.
CCP
Channel Selected
V
V
Remote 1 temperature
Local temperature
Remote 2 temperature
input. This allows the user
CCP
CC
ADT7467