ADT7460ARQZ-RL7 ONSEMI [ON Semiconductor], ADT7460ARQZ-RL7 Datasheet - Page 13

• Manufacturer Part Number: ADT7460ARQZ-RL7
• Description: dBCOOL Remote Thermal Monitor and Fan Controller
• Manufacturer: ONSEMI [ON Semiconductor]

SMBus Timeout
there is no SMBus activity for 25 ms, the ADT7460 assumes
that 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 it can be disabled.
Voltage Measurement Input
channel. It can also measure its own supply voltage, V
V
V
(Reg. 0x40) allows a 5.0 V supply to power the ADT7460
and be measured without over−ranging the V
measurement channel. The 2.5 V input can be used to
monitor a chipset supply voltage in computer systems.
Analog−to−Digital Converter
successive approximation, analog−to−digital converter.
This has a resolution of 10 bits. The basic input range is 0 V
Table 3. Configuration Register 1 (Reg. 0x40)
CC
CC
The ADT7460 includes an SMBus timeout feature. If
The ADT7460 has one external voltage measurement
Pin 14 may be configured to measure a 2.5 V supply. The
All analog inputs are multiplexed into the on−chip,
<6> TODIS
<6> TODIS
2. 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 ADT7460 has responded to the alert
supply voltage measurement is carried out through the
pin (Pin 3). Setting Bit 7 of Configuration Register 1
alert response address (ARA = 0001 100). This is
a general call address, which 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 the
device is now known, and it can be interrogated in
the usual way.
low, the one with the lowest device address has
priority in accordance with normal SMBus
arbitration.
response address, the master must read the status
registers and the SMBALERT is cleared only if
the error condition has gone away.
Bit
0: SMBus timeout enabled (default)
1: SMBus timeout disabled
Description
http://onsemi.com
CC
CC
ADT7460
.
13
to 2.25 V, but the input has built−in attenuators to allow
measurement of 2.5 V without any external components. To
allow the tolerance of the supply voltage, the ADC produces
an output of 3/4 full scale (768d or 0x300) for the nominal
input voltage and so has adequate headroom to deal with
overvoltages.
Input Circuitry
in Figure 23. The input circuit consists of an input protection
diode, an attenuator, plus a capacitor to form a first−order
low−pass filter that gives the input immunity to high
frequency noise.
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.
output codes of the 10−bit ADC.
voltage input in 711 ms and averages 16 conversions to
reduce noise; a measurement takes nominally 11.38 ms.
Table 4. Voltage Measurement Registers
Table 5. 2.5 V Limits Registers
The internal structure for the 2.5 V analog input is shown
Associated with the voltage measurement channels are a
Table 6 shows the input ranges of the analog inputs and
When the ADC is running, it samples and converts a
Register
Register
0x44
0x45
0x48
0x49
0x20
0x22
Figure 23. Structure of Analog Inputs
2.5V
IN
2.5 V high limit
2.5 V low limit
2.5 V reading
V
45kΩ
Description
V
V
Description
CC
CC
CC
94kΩ
high limit
low limit
reading
30pF
Default
Default
0x00
0x00
0xFF
0xFF
0x00
0x00