- 您現(xiàn)在的位置：買賣IC網 > PDF目錄384736 > MIC502 (Micrel Semiconductor,Inc.) FPGA - 100000 SYSTEM GATE 2.5 VOLT - NOT RECOMMENDED for NEW DESIGN PDF資料下載
參數(shù)資料
| 型號： | MIC502 |
| 廠商： | Micrel Semiconductor,Inc. |
| 元件分類： | FPGA |
| 英文描述： | FPGA - 100000 SYSTEM GATE 2.5 VOLT - NOT RECOMMENDED for NEW DESIGN |
| 中文描述： | 范進展信息管理IC |
| 文件頁數(shù)： | 10/11頁 |
| 文件大?。?/td> | 130K |
| 代理商： | MIC502 |
MIC502
Micrel
MIC502
172
May 1999
Referring to the “Typical Application,” the following approach
can be used to design the required thermistor interface
network:
Let
R1 =
∞
R
T1
= 13.6k
and
V
T
= 0.7V
DD
(70% of V
DD
)
Since
(at 70
°
C)
V =
V
R2
R
(
||R1+R2
DD
T1
×
)
0.7 =
R2
+R2
T1
R
(
)
0.7R
T1
+ 0.7R2 = R2
0.7R
T1
= 0.3R2
and
R2 = 2.33R
T1
= 2.33
×
13.6k = 31.7k
≈
33k
Let’s continue by determining what the temperature-propor-
tional voltage is at 25
°
C.
Let
R1 =
∞
and
R
T1
= 100k
From
(at 25
°
C).
V =V
R2
R
(
+R2
DD
T1
×
)
V =
V
100k+33k
(
V
T
= 0.248V
DD
Recalling from above discussion that the desired V
T
for 25
°
C
should be about 40% of V
DD
, the above value of 24.8% is far
too low. This would produce a voltage that would stop the fan
(recall from the above that this occurs when V
T
is about 30%
of V
DD
. To choose an appropriate value for R1 we need to
learn what the parallel combination of R
T1
and R1 should be
at 25
°
C:
Again
33k
DD
×
)
V =
V
R2
R
(
||R1+R2
DD
T1
×
)
0.4 =
R2
||R1+R2
R
(
T1
)
0.4(R
T1
|| R1) + 0.4R2 = R2
0.4(R
T1
|| R1) = 0.6R2
and
R
T1
|| R1 = 1.5R2 = 1.5
×
33k = 49.5k
Since
R
T1
= 100k
and
RT1 || R1 = 49.5k
≈
50k
let
R1 = 100k
While that solves the low temperature end of the range, there
is a small effect on the other end of the scale. The new value
of V
T
for 70
°
C is 0.734, or about 73% of V
DD
. This represents
only a 3% shift from the design goal of 70% of V
DD
. In
summary, R1 = 100k, and R2 = 33k. The candidate thermistor
used in this design example is the RL2010-54.1K-138-D1,
manufactured by Keystone Thermometrics.
The R25 resistance (100k
) of the chosen thermistor is
probably on the high side of the range of potential thermistor
resistances. The result is a moderately high-impedance
network for connecting to the V
T1
and/or V
T2
input(s). Be-
cause these inputs can have up to 1
μ
A of leakage current,
care must be taken if the input network impedance becomes
higher than the example. Leakage current and resistor accu-
racy could require consideration in such designs. Note that
the V
SLP
input has this same leakage current specification.
Secondary Fan-Control Input
The above discussions also apply to the secondary fan-
control input, VT2, pin 5. It is possible that a second ther-
mistor, mounted at another temperature-critical location out-
side the power supply, may be appropriate. There is also the
possibility of accommodating the NLX “FanC” signal via this
input. If a second thermistor is the desired solution, the VT2
input may be treated exactly like the VT1 input. The above
discussions then apply directly. If, however, the NLX FanC
signal is to be incorporated into the design then the operating
voltage (V
DD
= 5V vs. V
DD
= 12V) becomes a concern. The
FanC signal is derived from a 12V supply and is specified to
swing at least to 10.5V. A minimum implementation of the
FanC signal would provide the capability of asserting full-
speed operation of the fan; this is the case when 10.5V
≤
FanC
≤
12V. This FanC signal can be applied directly to the
VT2 input of the MIC502, but only when its V
DD
is 12V. If this
signal is required when the MIC502 V
DD
= 5V a resistor
divider is necessary to reduce this input voltage so it does not
exceed the MIC502 V
DD
voltage. A good number is 4V
(80%V
DD
).
Because of input leakage considerations, the impedance of
the resistive divider should be kept at
≤
100k
. A series
resistor of 120k
driven by the Fan C signal and a 100k
shunt resistor to ground make a good divider for driving the
V
T2
input.
Transistor and Base-Drive Resistor Selection
The OUT motor-drive output, pin 7, is intended for driving a
medium-power device, such as an NPN transistor. A rather
ubiquitous transistor, the 2N2222A, is capable of switching
up to about 400mA. It is also available as the PN2222A in a
plastic TO-92 package. Since 400mA is about the maximum
current for most popular computer power supply fans (with
many drawing substantially less current) and since the MIC502
provides a minimum of 10mA output current, the PN2222A,
with its minimum
β
of 40, is the chosen motor-drive transistor.
相關PDF資料 |
PDF描述 |
|---|---|
| MIC502BM | Replaced by PTN78060W,PTN78060H : |
| MIC502BN | Replaced by PTN78060W,PTN78060H : |
| mic5205 | 150mA Low-Noise LDO Regulator(輸出電流150mA低噪聲低壓差穩(wěn)壓器) |
| mic5210 | Dual 150mA LDO Regulator(輸出電流150mA 低壓差雙穩(wěn)壓器) |
| MIC5213-3.0BC5 | Teeny⑩ SC-70 レCap Low-Dropout Regulator Advance Information |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MIC502_06 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Fan Management IC |
| MIC502_11 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Fan Management IC |
| MIC5020 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Current-Sensing Low-Side MOSFET Driver |
| MIC5020_05 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Current-Sensing Low-Side MOSFET Driver |
| MIC5020BM | 功能描述:IC DRIVER MOSF LO SIDE HS 8-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - MOSFET，電橋驅動器 - 外部開關 系列:- 標準包裝:50 系列:- 配置:高端 輸入類型:非反相 延遲時間:200ns 電流 - 峰:250mA 配置數(shù):1 輸出數(shù):1 高端電壓 - 最大（自引導啟動）:600V 電源電壓:12 V ~ 20 V 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:8-DIP（0.300"，7.62mm） 供應商設備封裝:8-DIP 包裝:管件 其它名稱:*IR2127 |
發(fā)布緊急采購，3分鐘左右您將得到回復。