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參數(shù)資料
| 型號： | TC670ECH |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | Tiny Predictive Fan Failure Detector |
| 中文描述： | 微型風扇故障檢測預測 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 469K |
| 代理商： | TC670ECH |
TC670
DS21688B-page 6
2002 Microchip Technology Inc.
The design of the proper input SENSE circuitry is a
matter of scaling R
SENSE
to provide the necessary
amount of gain and proper selection of the sensing
capacitor. The following table (Table 4-1) lists some
recommended values for R
SENSE
according to the
nominal operating current of the fan. Please note that
the current draw specified by the fan manufacturer may
not be the fan’s nominal operating current, but a worst-
case rating. If the fan current falls between two of the
values listed, it is recommended that the higher value
resistor is used.
TABLE 4-1:
RECOMMENDED VALUES
FOR R
SENSE
PER FIGURE 4-2
A 0.1
μ
F ceramic capacitor is recommended for
C
SENSE
. Smaller capacitor values will require larger
sense resistors whereas larger capacitors are more
expensive and occupy more board space.
4.2
THRESHOLD Input
The voltage at the THRESHOLD input sets the
equivalent minimum allowable fan speed for the appli-
cation. As shown in Section 3.0 typical performance
curves, the relationship between the THRESHOLD
voltage and minimum fan speed is also power supply
and temperature dependant.
All the values for the THRESHOLD voltage that are
shown in these graphs represent typical numbers and
might not be optimized for all fans in all applications. To
ensure accurate fan speed monitoring of a specific fan
in a specific application, the user must perform a one-
time correlation check with the prototype.
There are two techniques that can be used to calibrate
the system. One approach is to find the fan’s full scale
capability and mathematically estimate the minimum
acceptable speed of the fan. A second technique is to
identify the fan’s minimum speed and calibrate the
THRESHOLD voltage accordingly.
4.2.1
THRESHOLD CALIBRATION USING
FAN’S FULL SCALE SPEED
The fan should first be run at full speed. At full speed
the THRESHOLD voltage level should be adjusted until
the ALERT output is asserted. With this full scale value
of the THRESHOLD voltage, the value can be scaled
down to the Fan Fault speed as a percentage of the full
speed. For example, if the fan full speed THRESHOLD
voltage is 1.5V, then the Fan Fault THRESHOLD
voltage at 30% of full speed would be 30% x 1.5V =
0.45V.
4.2.2
THRESHOLD CALIBRATION USING
FAN’S MINIMUM ALLOWABLE
SPEED ESTIMATE
For a more exact Fan Fault trip point, the user can run
the fan at its minimum allowed speed. At this speed, the
THRESHOLD voltage can be adjusted until the ALERT
output is asserted.
4.3
CLEAR Input
The CLEAR input allows the user to reset the ALERT
pin to a high status. This is an active HIGH input.
Consequently, as long as CLEAR is HIGH, ALERT will
always be HIGH as well. To allow ALERT to operate
correctly CLEAR must be held LOW. This feature can
be implemented so that false Fan Fault conditions do
not initiate system shutdown.
4.4
ALERT Output
The ALERT output is an open drain output capable of
sinking 2.5mA (typ). The ALERT output is asserted
whenever the detected fan speed equals or falls below
the equivalent voltage set at the THRESHOLD pin. The
ALERT output is only deactivated once the CLEAR pin
is brought to a HIGH state. Although the absolute
maximum output current of this pin is 25mA, it is
recommended that this current sinking into the ALERT
Output does not exceed 20mA.
4.5
Power Supply Input, V
DD
To assure proper operation of the TC670 in a noisy
environment where the fans are running, the V
DD
pin
(Pin 4) must be decoupled with a 0.1
μ
F capacitor as
shown in Figure 4-1. This capacitor should be located
as close to the TC670 V
DD
pin as possible as well being
promptly terminated to the ground plane. A Ceramic
capacitor is recommended.
4.6
Ground Terminal, GND
The GND pin (Pin 2) of the TC670 should be connected
directly to the analog ground plane of the circuit board.
Care should be taken in circuit layout to keep this pin
away from switching signals, such as the fan excitation
signals in order to avoid false signals on the SENSE
pin.
Nominal Fan Current
(mA)
R
SENSE
(
)
100
200
300
400
500
600
4.7
2.4
1.8
1.3
1.0
0.8
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| TC670ECHTR | 功能描述:馬達/運動/點火控制器和驅(qū)動器 Predictive Fan Failure Det RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| TC670ECHTR | 制造商:Microchip Technology Inc 功能描述:IC CONTROLLER FAN MANAGEMENT 制造商:Microchip Technology Inc 功能描述:IC, CONTROLLER, FAN MANAGEMENT |
| TC670ECHTR | 制造商:Microchip Technology Inc 功能描述:Fan Management Controller IC Package/Cas |
| TC670ECHTR-CUT TAPE | 制造商:Microchip 功能描述:TC670 Series 3 to 5.5 V Tiny Predictive Fan Failure Detector - SOT-23-6 |
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