 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ADT7462ACPZ-R7 Datasheet(PDF) 28 Page - ON Semiconductor |
|
|
|||||||||||||||||||||||||||||
ADT7462ACPZ-R7 Datasheet(HTML) 28 Page - ON Semiconductor |
|
|
28 / 81 page  ADT7462 http://onsemi.com 28 Figure 42. Interfacing Two Fans in Parallel to a PWM Output Using a Single N−Channel MOSFET ADT7462 PWM3 TACH3 TACH7 3.3 V 3.3 V 3.3 V +V +V TACH TACH Q1 NDT3055L 1N4148 5.0 V or 12 V FAN 5.0V or 12 V FAN 10 kΩ TYPICAL 10 kΩ TYPICAL 10 kΩ TYPICAL Fan Speed Measurement and Control TACH Inputs Pin 1, Pin 2, Pin 3, Pin 4, Pin 7, Pin 8, Pin 21, and Pin 22 are TACH inputs intended for fan speed measurement. Signal conditioning in the ADT7462 accommodates the slow rise and fall times typical of fan tachometer outputs. The maximum input signal range is 0 V to 5.0 V, even when VCC is less than 5.0 V. In the event that these inputs are supplied from fan outputs that exceed 0 V to 5.0 V, either resistive attenuation of the fan signal or diode clamping must be included to keep inputs within an acceptable range. Figure 43 to Figure 46 show circuits for most common fan TACH circuits. If the fan TACH output has a resistive pullup to VCC, it can be connected directly to the fan input, as shown in Figure 43. Figure 43. Fan with TACH Pullup to VCC 12 V VCC PULLUP TYPICAL TACH OUTPUT FAN SPEED COUNTER TACH ADT7462 4.7 kΩ If the fan output has a resistive pullup to 12 V (or other voltage greater than 5.0 V), the fan output can be clamped with a Zener diode, as shown in Figure 44. The Zener diode voltage should be chosen so that it is greater than VIH of the TACH input but less than 5.0 V, allowing for the voltage tolerance of the Zener diode. A value of between 3.0 V and 5.0 V is suitable. Figure 44. Fan with TACH Pullup to Voltage > 5.0 V, (Example 12 V) Clamped with Zener Diode 12 V VCC PULLUP TYPICAL TACH OUTPUT FAN SPEED COUNTER TACH ADT7462 ZD1* *CHOOSE ZD1 VOLTAGE APPROXIMATELY 0.8 y VCC. 4.7 kΩ If the fan has a strong pullup (less than 1 k W) to 12 V or a totem−pole output, a series resistor can be added to limit the Zener current, as shown in Figure 45. Alternatively, a resistive attenuator can be used, as shown in Figure 46. R1 and R2 should be chosen such that: 2.0 V < VPULLUP × R2/(RPULLUP + R1 + R2) < 5.0 V The fan inputs have an input resistance of nominally 160 k W to ground, so this should be taken into account when calculating resistor values. With a pullup voltage of 12 V and a pullup resistor of less than 1 k W, suitable values for R1 and R2 would be 100 kW and 47 k W. This gives a high input voltage of 3.83 V. Figure 45. Fan with Strong TACH Pullup to >VCC or Totem−Pole Output, Clamped with Zener Diode and Resistor 5.0 V or 12 V VCC PULLUP TYP or TOTEM POLE TACH OUTPUT FAN SPEED COUNTER TACH ADT7462 ZD1 ZENER* FAN *CHOOSE ZD1 VOLTAGE APPROXIMATELY 0.8 y VCC. < 1 kΩ R1 10 kΩ Figure 46. Fan with Strong TACH Pullup to >VCC or Totem−Pole Output, Attenuated with R1/R2 12 V VCC TACH OUTPUT FAN SPEED COUNTER TACH ADT7462 R2* *SEE TEXT R1* < 1 kΩ Fan Speed Measurement The method of fan speed measurement when using 3−wire fans differs from that used with 4−wire fans. When 3−wire |
|
Link URL |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link to Datasheet | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
British ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
