參數(shù)資料
型號(hào)： ADT7460
廠(chǎng)商： Analog Devices, Inc.
英文描述： dB COOL?? Remote Thermal Controller and Fan Controller
中文描述： 分貝很酷吧？？遠(yuǎn)程熱控制器和風(fēng)扇控制器
文件頁(yè)數(shù)： 22/48頁(yè)
文件大?。?/td> 695K
代理商： ADT7460
REV. 0
–22–
ADT7460
THERM
limit time. For example, if it takes one week for a
THERM
limit of 2.914 s to be exceeded and the next time it only
takes 1 hour, then this is an indication of a serious degradation
in system performance.
Configuring the ADT7460
THERM
Pin as an Output
In addition to the ADT7460 being able to monitor
THERM
as
an input, the ADT7460 can optionally drive
THERM
low as an
output. The user can preprogram system critical thermal limits.
If the temperature exceeds a thermal limit by 0.25
°
C,
THERM
will assert low. If the temperature is still above the thermal limit
on the next monitoring cycle,
THERM
will stay low.
THERM
will remain asserted low until the temperature is equal to or
below the thermal limit. Since the temperature for that channel
is only measured every monitoring cycle, once
THERM
asserts
it is guaranteed to remain low for at least one monitoring cycle.
The
THERM
pin can be configured to assert low if the Remote 1,
Local, or Remote 2 Temperature
THERM
Limits get exceeded
by 0.25
°
C. The
THERM
Limit Registers are at locations 0x6A,
0x6B, and 0x6C respectively. Setting Bit 3 of Registers 0x5F,
0x60, and 0x61 enables the
THERM
output feature for the
Remote 1, Local, and Remote 2 Temperature channels, respec-
tively. Figure 27 shows how the
THERM
pin asserts low as an
output in the event of a critical overtemperature.
THERM LIMIT
+0.25 C
THERM LIMIT
TEMP
THERM
ADT7460
MONITORING
CYCLE
Figure 27. Asserting
THERM
as an Output, Based on
Tripping
THERM
Limits
FAN DRIVE USING PWM CONTROL
The ADT7460 uses Pulsewidth Modulation (PWM) to control
fan speed. This relies on varying the duty cycle (or on/off ratio)
of a square wave applied to the fan to vary the fan speed. The
external circuitry required to drive a fan using PWM control is
extremely simple. A single NMOSFET is the only drive device
required. The specifications of the MOSFET depend on the
maximum current required by the fan being driven. Typical
notebook fans draw a nominal 170 mA, and so SOT devices can
be used where board space is a concern. In desktops, fans can
typically draw 250 mA–300 mA each. If you drive several fans
in parallel from a single PWM output or drive larger server fans,
the MOSFET will need to handle the higher current requirements.
The only other stipulation is that the MOSFET should have a
gate voltage drive, V
GS
< 3.3 V for direct interfacing to the
PWM_OUT pin. V
GS
can be greater than 3.3 V as long as the
pull-up on the gate is tied to 5 V. The MOSFET should also
have a low on resistance to ensure that there is not significant
voltage drop across the FET. This would reduce the voltage
applied across the fan and therefore the maximum operating
speed of the fan.
Figure 28 shows how a 3-wire fan may be driven using PWM
control.
ADT7460
TACH/AIN
PWM
4.7k
10k
10k
10k
3.3V
12V
12V
12V
FAN
Q1
NDT3055L
TACH
1N4148
Figure 28. Driving a 3-Wire Fan Using an
N-Channel MOSFET
Figure 28 uses a 10 k
pull-up resistor for the TACH signal. This
assumes that the TACH signal is open-collector from the fan. In
all cases, the TACH signal from the fan
must
be kept below 5 V
maximum to prevent damaging the ADT7460. If in doubt as to
whether the fan used has an open-collector or totem pole
TACH output, use one of the input signal conditioning circuits
shown in the Fan Speed Measurement
section of the data sheet.
Figure 29 shows a fan drive circuit using an NPN transistor
such as a general-purpose MMBT2222. While these devices are
inexpensive, they tend to have much lower current handling
capabilities and higher on-resistance than MOSFETs. When
choosing a transistor, care should be taken to ensure that it
meets the fan’s current requirements.
Ensure that the base resistor is chosen such that the transistor is
saturated when the fan is powered on.
ADT7460
TACH/AIN
PWM
4.7k
10k
10k
470
3.3V
12V
12V
12V
FAN
Q1
MMBT2222
1N4148
TACH
Figure 29. Driving a 3-Wire Fan Using an NPN Transistor
Driving Two Fans from PWM3
Note that the ADT7460 has four TACH inputs available for fan
speed measurement, but only three PWM drive outputs. If a
fourth fan is being used in the system, it should be driven from
the PWM3 output in parallel with the third fan. Figure 30 shows
how to drive two fans in parallel using low cost NPN transistors.
Figure 31 is the equivalent circuit using the NDT3055L
MOSFET. Note that since the MOSFET can handle up to 3.5 A,
it is simply a matter of connecting another fan directly in parallel
with the first.
相關(guān)PDF資料
PDF描述
ADT7460ARQ dB COOL?? Remote Thermal Controller and Fan Controller
ADT7461 【1∑C Temperature Monitor with Series Resistance Cancellation
ADT7461AR 【1∑C Temperature Monitor with Series Resistance Cancellation
ADT7461AR-REEL 【1∑C Temperature Monitor with Series Resistance Cancellation
ADT7461AR-REEL7 【1∑C Temperature Monitor with Series Resistance Cancellation
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
ADT7460ARQ 功能描述:IC REMOTE THRML/FAN CTRLR 16QSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 熱管理 系列:dBCool® 標(biāo)準(zhǔn)包裝:1 系列:- 功能:溫度監(jiān)控系統(tǒng)（傳感器） 傳感器類(lèi)型:內(nèi)部和外部 感應(yīng)溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠(yuǎn)程（最大值） 拓?fù)?ADC，比較器，寄存器庫(kù) 輸出類(lèi)型:2 線(xiàn) SMBus? 輸出警報(bào):無(wú) 輸出風(fēng)扇:無(wú) 電源電壓:2.7 V ~ 5.5 V 工作溫度:-40°C ~ 125°C 安裝類(lèi)型:表面貼裝 封裝/外殼:SOT-23-8 供應(yīng)商設(shè)備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱(chēng):296-22675-6
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ADT7460ARQ-REEL7 功能描述:IC SENSOR TEMP FAN-CTRL 16QSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 熱管理 系列:dBCool® 標(biāo)準(zhǔn)包裝:1 系列:- 功能:溫度監(jiān)控系統(tǒng)（傳感器） 傳感器類(lèi)型:內(nèi)部和外部 感應(yīng)溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠(yuǎn)程（最大值） 拓?fù)?ADC，比較器，寄存器庫(kù) 輸出類(lèi)型:2 線(xiàn) SMBus? 輸出警報(bào):無(wú) 輸出風(fēng)扇:無(wú) 電源電壓:2.7 V ~ 5.5 V 工作溫度:-40°C ~ 125°C 安裝類(lèi)型:表面貼裝 封裝/外殼:SOT-23-8 供應(yīng)商設(shè)備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱(chēng):296-22675-6
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ADT7460ARQZ-R7 制造商:ON Semiconductor 功能描述:Temp Sensor Digital Serial (3-Wire) 16-Pin QSOP T/R
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