- 您现在的位置：买卖IC网 > Sheet目录1194 > ADT7490ZEVB (ON Semiconductor)BOARD EVALUATION FOR ADT7490
ADT7490
12 V
12 V
3.3 V
TACH
ADT7490
PWM
10 k W
10 k W
TACH
4.7 k W
3.3 V
2 k W
12 V, 4-WIRE FAN
V CC
TACH
PWM
TACH4
ADT7490
TACH3
10 k W
TYP
3.3 V
10 k W
TYP
3.3 V
3.3 V
TACH
3.3 V
+V
5V
or
12 V
FAN
TACH
+V
5V
or
12 V
FAN
Figure 38. Driving a 4-wire Fan
Driving Two Fans from PWM3
PWM3
10 k W
TYP
Q1
NDT3055L
The ADT7490 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 39 shows how to drive two fans in parallel using
low cost NPN transistors. Figure 40 shows the equivalent
circuit using a MOSFET.
Because the MOSFET can handle up to 3.5 A, it is simply
a matter of connecting another fan directly in parallel with
Figure 40. Interfacing Two Fans in Parallel to the
PWM3 Output Using a Single N-channel MOSFET
Laying Out 3-wire Fans
Figure 41 shows how to lay out a common circuit
arrangement for 3-wire fans.
12 V or 5 V
the first. Care should be taken in designing drive circuits
with transistors and FETs to ensure the PWM outputs are not
required to source current, and that they sink less than the
5 mA maximum current specified in the data sheet.
Driving up to Three Fans from PWM3
TACH measurements for fans are synchronized to
particular PWM channels; for example, TACH1 is
TACH
R1
R2
R3
1N4148
3.3 V or 5 V
R4
Q1
MMBT2222
PWM
synchronized to PWM1. TACH3 and TACH4 are both
synchronized to PWM3, so PWM3 can drive two fans.
Alternatively, PWM3 can be programmed to synchronize
TACH2, TACH3, and TACH4 to the PWM3 output. This
allows PWM3 to drive two or three fans. In this case, the
drive circuitry looks the same, as shown in Figure 39 and
Figure 40. The SYNC bit in Register 0x62 enables this
function.
Synchronization is not required in high frequency mode
when used with 4-wire fans.
SYNC, Enhanced Acoustics Register 1 (Register 0x62)
Bit 4 (SYNC) = 1, synchronizes TACH2, TACH3, and
TACH4 to PWM3.
Figure 41. Planning for 3-wire Fans on a PCB
TACH Inputs
Pin 9, Pin 11, Pin 12, and Pin 14 (when configured as
TACH inputs) are high impedance inputs intended for fan
speed measurement.
Signal conditioning in the ADT7490 accommodates the
slow rise and fall times typical of fan tachometer outputs. The
maximum input signal range is 0 V to 3.6 V, even though V CC
is 3.3 V. In the event that these inputs are supplied from fan
outputs that exceed 0 V to 3.6 V, either resistive attenuation
of the fan signal or diode clamping must be included to keep
inputs within an acceptable range.
Figure 42 to Figure 45 show circuits for the most common
3.3 V
ADT7490
PWM3
3.3 V
1 k W
TACH3
3.3 V
Q1
12 V
TACH4
3.3 V
fan TACH outputs.
If the fan TACH output has a resistive pullup to V CC , it can
12 V V CC
2.2 k W
MMBT3904
Q2
PULLUP
10 k W
10 k W
MMBT2222
Q3
MMBT2222
4.7 k W
TYP
TACH
OUTPUT
TACH
ADT7490
FAN SPEED
COUNTER
Figure 39. Interfacing Two Fans in Parallel to the
PWM3 Output Using Low Cost NPN Transistors
http://onsemi.com
29
Figure 42. Fan with TACH Pullup to V CC
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
ADZS-21262-1-EZEXT
BOARD DAUGHTER FOR ADSP-21262
ADZS-BF-EZEXT-1
BOARD DAUGHTER ADSP-BF533/561KIT
ADZS-BFAV-EZEXT
BOARD DAUGHT ADSP-BF533,37,61KIT
ADZS-BFSHUSB-EZEXT
BOARD DAUGHTER EZ EXTENDER
ADZS-BRKOUT-EX3
ADZS-BRKOUT-EX3
ADZS-SHAUDIO-EZEXT
SHARC AUDIO EZ-EXTENDER
ADZS-WVGALCD-EX3
BOARD EXTENDER WVGA/LCD EI3
AGA-3
FUSE 3A 125VAC 1AG FAST
相关代理商/技术参数
ADT75
制造商:AD 制造商全称:Analog Devices 功能描述:+-1∑C Accurate, 12-Bit Digital Temperature Sensor
ADT7516
制造商:AD 制造商全称:Analog Devices 功能描述:SPI/I2C Compatible, Temperature Sensor, Four Channel ADC and Quad Voltage Output DAC
ADT7516_06
制造商:AD 制造商全称:Analog Devices 功能描述:SPI-/I2C-Compatible, Temperature Sensor,4-Channel ADC and Quad Voltage Output
ADT7516ARQ
功能描述:IC TEMP SNSR QUAD DAC 16-QSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 热管理 系列:- 标准包装:2,500 系列:SilentSense™ 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:-55°C ~ 125°C，外部传感器 精确度:±2°C 本地（最大），±3°C 远程（最大） 拓扑:ADC（三角积分型），比较器，寄存器库 输出类型:I²C?/SMBus? 输出警报:是 输出风扇:是 电源电压:2.7 V ~ 5.5 V 工作温度:-55°C ~ 125°C 安装类型:表面贴装 封装/外壳:8-TSSOP，8-MSOP（0.118"，3.00mm 宽） 供应商设备封装:8-MSOP 包装:带卷 (TR) 其它名称:MIC284-2BMMTRMIC284-2BMMTR-ND
ADT7516ARQ-REEL
制造商:Analog Devices 功能描述:Temp Sensor Digital Serial (4-Wire, SPI, I2C) 16-Pin QSOP T/R 制造商:Analog Devices 功能描述:TEMP SENSOR DGTL SERL (4-WIRE, SPI) 16QSOP - Tape and Reel
ADT7516ARQ-REEL7
制造商:Analog Devices 功能描述:Temp Sensor Digital Serial (4-Wire, SPI, I2C) 16-Pin QSOP T/R 制造商:Analog Devices 功能描述:TEMP SENSOR DGTL SERL (4-WIRE, SPI) 16QSOP - Tape and Reel
ADT7516ARQZ
功能描述:IC TEMP SNSR QUAD DAC 16-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热管理 系列:- 标准包装:3,000 系列:- 功能:温度开关 传感器类型:内部 感应温度:85°C 分界点 精确度:±6°C（最小值） 拓扑:ADC（三角积分型），比较器，寄存器库 输出类型:开路漏极 输出警报:是 输出风扇:是 电源电压:2.7 V ~ 5.5 V 工作温度:-55°C ~ 125°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:带卷 (TR) 其它名称:ADT6501SRJZP085RL7-ND
ADT7516ARQZ-REEL
制造商:Analog Devices 功能描述:Temp Sensor Digital Serial (4-Wire, SPI, I2C) 16-Pin QSOP T/R