参数资料
型号: NCT1008DMT3R2G
厂商: ON Semiconductor
文件页数: 14/20页
文件大小: 327K
描述: TMP DIO MON/SMBUS 4CH 8WDFN
标准包装: 3,000
功能: 温度监控系统(传感器)
传感器类型: 内部和外部
感应温度: 0°C ~ 127°C,-64°C ~ 191°C
精确度: ±2.5°C(最小值)
拓扑: ADC(三角积分型),比较器,多路复用器,寄存器库
输出类型: I²C?/SMBus?
输出警报:
输出风扇:
电源电压: 2.8 V ~ 3.6 V
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 8-WFDFN
供应商设备封装: 8-WDFN(2x2)
包装: 带卷 (TR)
NCT1008
http://onsemi.com
14
When reading data from a register there are two
possibilities.
?SPAN class="pst NCT1008DMT3R2G_2296461_3"> If the address pointer register value of the NCT1008 is
unknown or not the desired value, it is first necessary to
set it to the correct value before data can be read from
the desired data register. This is done by writing to the
NCT1008 as before, but only the data byte containing
the register read address is sent, because data is not to
be written to the register see Figure 16.
A read operation is then performed consisting of the
serial bus address, R/W
 bit set to 1, followed by the
data byte read from the data register see Figure 17.
?SPAN class="pst NCT1008DMT3R2G_2296461_3"> If the address pointer register is known to be at the
desired address, data can be read from the corresponding
data register without first writing to the address pointer
register and the bus transaction shown in Figure 16 can
be omitted.
Notes:
?SPAN class="pst NCT1008DMT3R2G_2296461_3"> It is possible to read a data byte from a data register
without first writing to the address pointer register.
However, if the address pointer register is already at the
correct value, it is not possible to write data to a register
without writing to the address pointer register because
the first data byte of a write is always written to the
address pointer register.
?SPAN class="pst NCT1008DMT3R2G_2296461_3"> Some of the registers have different addresses for read
and write operations. The write address of a register
must be written to the address pointer if data is to be
written to that register, but it may not be possible to
read data from that address. The read address of a
register must be written to the address pointer before
data can be read from that register.
ALERT
 Output
This is applicable when Pin 6 is configured as an ALERT
output. The ALERT
  output goes low whenever an
out-of-limit measurement is detected, or if the remote
temperature sensor is open circuit. It is an open-drain output
and requires a pullup resistor to V
DD
. Several ALERT
 outputs
can be wire-ORed together, so that the common line goes
low if one or more of the ALERT
 outputs goes low.
The ALERT
 output can be used as an interrupt signal to a
processor, or as an SMBALERT
. Slave devices on the SMBus
cannot normally signal to the bus master that they want to
talk, but the SMBALERT
 function allows them to do so.
One or more ALERT
  outputs can be connected to a
common SMBALERT
 line that is connected to the master.
When the SMBALERT
 line is pulled low by one of the
devices, the following procedure occurs (see Figure 18):
Figure 18. Use of SMBALERT
ALERT RESPONSE
ADDRESS
MASTER SENDS
ARA AND READ
COMMAND
DEVICE SENDS
ITS ADDRESS
RD
START
ACK
DEVICE
ADDRESS
NO
ACK
STOP
MASTER RECEIVES SMBALERT
1. SMBALERT
 is pulled low.
2. Master initiates a read operation and sends the
alert response address (ARA = 0001 100). This is
a general call address that must not be used as a
specific device address.
3. The device whose ALERT
 output is low responds
to the alert response address and the master reads
its device address. As the device address is seven
bits, an LSB of 1 is added. The address of the
device is now known and it can be interrogated in
the usual way.
4. If more than one devices ALERT
 output is low,
the one with the lowest device address takes
priority, in accordance with normal SMBus
arbitration.
Once the NCT1008 has responded to the alert response
address, it resets its ALERT
 output, provided that the error
condition that caused the ALERT
 no longer exists. If the
SMBALERT
 line remains low, the master sends the ARA
again, and so on until all devices whose ALERT
 outputs
were low have responded.
Low Power Standby Mode
The NCT1008 can be put into low power standby mode by
setting Bit 6 of the configuration register. When Bit 6 is low,
the NCT1008 operates normally. When Bit 6 is high, the
ADC is inhibited, and any conversion in progress is
terminated without writing the result to the corresponding
value register. However, the SMBus is still enabled. Power
consumption in the standby mode is reduced to 5 mA if there
is no SMBus activity, or 30 mA if there are clock and data
signals on the bus.
When the device is in standby mode, it is possible to
initiate a one-shot conversion of both channels by writing to
the one-shot register (Address 0x0F), after which the device
returns to standby. It does not matter what is written to the
one-shot register, all data written to it is ignored. It is also
possible to write new values to the limit register while in
standby mode. If the values stored in the temperature value
registers are outside the new limits, an ALERT
 is generated,
even though the NCT1008 is still in standby.
1.8 V Logic Operation
The NCT1008 is 1.8 V logic compatible; this means that
the communication lines (SDA and SCL) and THERM
 can
be pulled up to a 1.8 V supply while still remaining within
spec.
The ALERT
/THERM2
 pin is also 1.8 V logic compatible,
however, in order to keep the quiescent current to its
minimum, it is recommended that this pin is pulled to V
DD
.
Sensor Fault Detection
At its D+ input, the NCT1008 contains internal sensor
fault detection circuitry. This circuit can detect situations
where an external remote diode is either not connected or
incorrectly connected to the NCT1008. A simple voltage
comparator trips if the voltage at D+ exceeds V
DD
1.0 V
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