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参数资料
| 型号： | MC74LCX2952SD |
| 厂商： | ON SEMICONDUCTOR |
| 元件分类： | 总线收发器 |
| 英文描述： | LVC/LCX/Z SERIES, 8-BIT REGISTERED TRANSCEIVER, TRUE OUTPUT, PDSO24 |
| 封装： | PLASTIC, SSOP-24 |
| 文件页数： | 33/43页 |
| 文件大小： | 383K |
| 代理商： | MC74LCX2952SD |
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Reliability Information
LCX DATA
BR1339 — REV 3
249
MOTOROLA
TJ = (ΘJA × PD) + TA
where:
TJ
= Junction Temperature (
°C)
ΘJA = Thermal Resistance (Junction–to–Ambient)
PD
= Power Dissipation at a TJ
TA
= Ambient Temperature (
°C)
Example of LCX TJ Calculation
1. Calculate Current Consumption:
For example, the LCX244’s CP is 25pF. Let VCC = 3V;
operating temperature = 85
°C; FOUT = 50MHz; for 4 outputs
switching; hold 2 inputs LOW and 2 inputs HIGH (at VCC –
0.6V); CL = 100pF; 500 pull–down; no pull–up.
25pF
3V
4
i
+1
50MHz
) 0.3mA(2)
12
=15mA + 0.6mA = 15.6mA
These unloaded terms contribute only 10% of the total ICC
current.
(2.8V
* 0.2V)
4
i
+1
100pF(50MHz)
)
6
i
+1
2.8V
500
W
34
= 52mA + 33.6mA = 85.6mA
In this example, terms three and four contribute over 55%
of the total ICC current. This part of ICC is entirely due to
external loading.
(2.8V
* 0.2V)
4
I
+1
100pF(50MHz)
)
6
I
+1
3V
* 0.2V
R
56
= 52mA + 0 = 52mA
These terms are not ICC currents, but rather currents
“sinked” by the lower structure of the device. The total current
from all terms is 153.2mA.
2. Finding PD (V x I)
When calculating the total power dissipation of the device,
the first two terms are multiplied by VCC, which in this
example is
3V(15.6mA) = 46.8mW
The third and fourth terms are multiplied by the voltage
drop across the upper structure of the device, VCC–VOH. This
is approximately 0.2V.
0.2V(85.6mA) = 17.1mW
The fifth and sixth terms are multiplied by the voltage drop
across the lower structure of the device, VOL.
0.2V(52mA) = 10.4mW
The total estimated power dissipation of an LCX 244 with 4
outputs switching, at 85
°C, with VCC=3V, with 2 outputs held
static Low, and 2 inputs at 2.4V with 100pF capacitive loads,
500
pull–downs, and 50MHz switching frequency is:
74.3 mW
3.
ΘJA Value
The
θJA for a 20–pin TSSOP is approximately 128°C/W.
4. Final Calculations for TJ for the LCX244
TJ = (PD × ΘJA) + TA = (0.0743W × 128°C/W) + 85°C =
94.5
°C. LCX runs cool — well below the point for reliability
worries. Using the Arrhenius Equation (Eq 1 on page 247),
the time to 0.1% bond failures is approximately 30 years.
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| MC74LCX32DR2 | 功能描述:逻辑门 2-3.6V Quad 2-Input RoHS:否 制造商:Texas Instruments 产品:OR 逻辑系列:LVC 栅极数量:2 线路数量（输入/输出）:2 / 1 高电平输出电流:- 16 mA 低电平输出电流:16 mA 传播延迟时间:3.8 ns 电源电压-最大:5.5 V 电源电压-最小:1.65 V 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:DCU-8 封装:Reel |
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