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參數(shù)資料
| 型號： | MC14489DW |
| 廠商： | MOTOROLA INC |
| 元件分類： | 顯示驅動器 |
| 英文描述： | Digital Signal Processor 181-CPGA -55 to 125 |
| 中文描述： | LED DISPLAY DRIVER, PDSO20 |
| 封裝： | SOP-20 |
| 文件頁數(shù)： | 18/20頁 |
| 文件大?。?/td> | 303K |
| 代理商： | MC14489DW |
MC14489
18
MOTOROLA
THERMAL CONSIDERATIONS
The MC14489 is designed to operate with a
chip–junction
temperature (TJ) ranging from – 40 to 130
°
C, as indicated in
the electrical characteristics tables. The
ambient
operating
temperature range (TA) is dependent on R
θ
JA, the internal
chip current, how many anode drivers are used, the number
of bank drivers used, the drive current, and how the package
is cooled. The maximum ratings table gives the thermal re-
sistance, junction–to–ambient, of the MC14489 mounted on
a pc board using natural convection to be 90
°
C per watt for
the plastic DIP. The SOG thermal resistance is 100
°
C per
watt.
The following general equation (1) is used to determine the
power dissipated by the MC14489.
PT = PD + PI
(1)
where
PT= Total power dissipation of the MC14489
PD= Power dissipated in the driver circuitry (mW)
PI= Power dissipated by the internal chip
circuitry (mW)
The equations for the two terms of the general equation
are:
PD = (iOH) (N)(VDD – VLED)(B/5)
(2)
(3)
PI = (1.5 mA)(VDD) + IRx(VDD – IRxRx)
where
iOH= Peak anode driver current (mA)
IRx= iOH /10, with iOH = the peak anode driver current
(mA) when the dimmer bit is high
N = Number of anode drivers used
B = Number of bank drivers used
Rx = External resistor value (k
)
VDD= Maximum supply voltage, referenced to VSS
(volts)
VLED= Minimum anticipated voltage drop across the
LED
1.5 mA = Operating supply current of the MC14489
The following two examples show how to calculate the
maximum allowable ambient temperature.
Worst–Case Analysis Example 1:
5–digit display with decimals (5 banks and 8 anode drivers)
DIP without heat sink on PC board
iOH= 20 mA max
VLED= 1.8 V min
VDD= 5.25 max
PD = (20)(8)(5.25 – 1.8)(5/5) = 552 mW
Ref. (2)
PI = (1.5)(5.25) + 2[5.25 – 2(2)] = 10 mW
Ref. (3)
Therefore, PT = 552 + 10 = 562 mW
and
Tchip = R
θ
JAPT = (90
°
C/W)(0.562) = 51
°
C
Finally, the maximum allowable
TA = TJmax –
Tchip = 130 – 51 = 79
°
C
That is, if TA = 79
°
C, the maximum junction temperature is
130
°
C. The chip’s average temperature for this example is
lower than 130
°
C because all segments are usually not illu-
minated simultaneously for an indefinite period.
Ref. (1)
Worst–Case Analysis Example 2:
16 lamps (4 banks and 4 anode drivers)
SOG without heat sink on PC board
iOH= 30 mA max
VLED= 1.8 V min
VDD= 5.5 max
PD = (30)(4)(5.5 – 1.8)(4/5) = 355 mW
PI = (1.5)(5.5) + 3[5.5 – 3(1.0)] = 16 mW
Ref. (2)
Ref. (3)
Therefore, PT = 355 + 16 = 371 mW
and
Tchip = R
θ
JAPT = (100
°
C/W)(0.371) = 37
°
C
Finally, the maximum allowable
TA = TJmax –
Tchip = 130 – 37 = 93
°
C
Ref. (1)
To extend the allowable ambient temperature range or to
reduce TJ, which extends chip life, a heat sink such as
shown in Figure 20 can be used in high–current applications.
Alternatively, heat–spreader techniques can be used on the
PC board, such as running a wide trace under the MC14489
and using thermal paste. Wide, radial traces from the
MC14489 leads also act as heat spreaders.
AAVID #5804 or equivalent
(Tel. 603/524–4443, FAX 603/528–1478)
Motorola cannot recommend one supplier over another and
in no way suggests that this is the only heat sink supplier.
Figure 20. Heat Sink
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相關代理商/技術參數(shù) |
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|---|---|
| MC14489P | 制造商:Motorola Inc 功能描述: |
| MC14490DW | 功能描述:算數(shù)邏輯單元 - ALU LOG CMOS 3-18V HEX BOUNCE ELIMINATOR RoHS:否 制造商:ON Semiconductor 高電平輸出電流: 低電平輸出電流: 傳播延遲時間: 電源電壓-最大:18 V 電源電壓-最小:3 V 封裝 / 箱體:SOIC-16 Wide 最大工作溫度:+ 125 C 封裝:Reel |
| MC14490DWG | 功能描述:算數(shù)邏輯單元 - ALU LOG CMOS 3-18V HEX BOUNCE ELIMINATOR RoHS:否 制造商:ON Semiconductor 高電平輸出電流: 低電平輸出電流: 傳播延遲時間: 電源電壓-最大:18 V 電源電壓-最小:3 V 封裝 / 箱體:SOIC-16 Wide 最大工作溫度:+ 125 C 封裝:Reel |
| MC14490DWG | 制造商:ON Semiconductor 功能描述:Gate / Inverter Logic IC Package/Case:16 |
| MC14490DWR2 | 功能描述:算數(shù)邏輯單元 - ALU LOG CMOS 3-18V HEX BOUNCE ELIMINATOR RoHS:否 制造商:ON Semiconductor 高電平輸出電流: 低電平輸出電流: 傳播延遲時間: 電源電壓-最大:18 V 電源電壓-最小:3 V 封裝 / 箱體:SOIC-16 Wide 最大工作溫度:+ 125 C 封裝:Reel |
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