ADT7476ARQZ ON Semiconductor, ADT7476ARQZ Datasheet - Page 13

• Manufacturer Part Number: ADT7476ARQZ
• Description: IC REMOTE THERMAL CTRLR 24QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7476ARQZ

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-QSOP
• Full Temp Accuracy: +/- 0.5 C
• Digital Output - Bus Interface: Serial (3-Wire, 4-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SMBus Timeout
there is no SMBus activity for 35 ms, the ADT7476 assumes
the bus is locked and releases the bus. This prevents the
device from locking or holding the SMBus expecting data.
Some SMBus controllers cannot handle the SMBus timeout
feature, so if necessary, it can be disabled.
Configuration Register 1 (0x40)
Virus Protection
critical ADT7476 register settings, the lock bit can be set.
Setting Bit 1 of Configuration Register 1 (0x40) sets the lock
bit and locks critical registers. In this mode, certain registers
can no longer be written to until the ADT7476 is powered
down and powered up again. For more information on which
registers are locked see Table 14.
Voltage Measurement Input
channels. It can also measure its own supply voltage, V
Pin 20 to Pin 23 can measure 5.0 V, 12 V, and 2.5 V supplies,
and the processor core voltage V
V
V
chipset supply voltage in computer systems.
Analog−to−Digital Converter
successive−approximation, analog−to−digital converter,
which has a resolution of 10 bits. The basic input range is 0 V
to 2.25 V, but the inputs have built−in attenuators to allow
measurement of 2.5 V, 3.3 V, 5.0 V, 12 V, and the processor
core voltage V
allow the tolerance of these supply voltages, the ADC
produces an output of 3/4 full scale (768 dec or 300 hex) for
CC
CC
The ADT7476 includes an SMBus timeout feature. If
To prevent rogue programs or viruses from accessing
The ADT7476 has four external voltage measurement
All analog inputs are multiplexed into the on−chip,
[6] TODIS = 0, SMBus timeout enabled (default).
[6] TODIS = 1, SMBus timeout disabled.
2. The master initiates a read operation and sends the
3. The device whose SMBALERT output is low
4. If more than one device’s SMBALERT output is
5. Once the ADT7476 responds to the alert response
supply voltage measurement is carried out through the
pin (Pin 4). The 2.5 V input can be used to monitor a
alert response address (ARA = 0001 100). This is
a general call address that must not be used as a
specific device address.
responds to the alert response address, and the
master reads its device address. The address of this
device is now known and can be interrogated per
usual.
low, the one with the lowest device address has
priority in accordance with normal SMBus
arbitration.
address, the master must read the status registers,
and SMBALERT is cleared only if the error
condition goes away.
CCP
without any external components. To
CCP
(0 V to 3 V input). The
http://onsemi.com
CC
.
13
the nominal input voltage, giving it adequate headroom to
cope with overvoltages.
Input Circuitry
Figure 24 The input circuit consists of an input protection
diode, an attenuator, plus a capacitor to form a first−order
low−pass filter that gives input immunity to high frequency
noise.
Voltage Measurement Registers
Register 0x20, 2.5 V Reading = 0x00 default
Register 0x21, V
Register 0x22, V
Register 0x23, 5.0 V Reading = 0x00 default
Register 0x24, 12 V Reading = 0x00 default
Voltage Limit Registers
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 0x44, 2.5 V Low Limit = 0x00 default
Register 0x45, 2.5 V High Limit = 0xFF default
Register 0x46, V
Register 0x47, V
Register 0x48, V
Register 0x49, V
Register 0x4A, 5.0 V Low Limit = 0x00 default
Register 0x4B, 5.0 V High Limit = 0xFF default
Register 0x4C, 12 V Low Limit = 0x00 default
Register 0x4D, 12 V High Limit = 0xFF default
output codes of the 10−bit ADC.
The internal structure for the analog inputs is shown in
Associated with each voltage measurement channel is a
Table 5 shows the input ranges of the analog inputs and
Figure 24. Structure of Analog Inputs
2.5V
12V
V
5V
V
CCP
CC
IN
IN
IN
CCP
CC
CCP
CCP
CC
CC
17.5kΩ
120kΩ
Reading = 0x00 default
High Limit = 0xFF default
Low Limit = 0x00 default
93kΩ
68kΩ
45kΩ
Reading = 0x00 default
Low Limit = 0x00 default
High Limit = 0xFF default
52.5kΩ
20kΩ
47kΩ
71kΩ
94kΩ
30pF
30pF
30pF
30pF
35pF
MUX