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| 型号： | MC74AC00DT |
| 厂商： | ON SEMICONDUCTOR |
| 元件分类： | 门电路 |
| 英文描述： | AC SERIES, QUAD 2-INPUT NAND GATE, PDSO14 |
| 封装： | PLASTIC, TSSOP-14 |
| 文件页数： | 27/45页 |
| 文件大小： | 434K |
| 代理商： | MC74AC00DT |
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37
TTL-Compatible CMOS Designs Require Delta ICC
Consideration
The FACT product line is comprised of two types of
advanced CMOS circuits: ‘AC and ‘ACT devices. ‘ACT
indicates an advanced CMOS device with TTL-type input
thresholds for direct replacement of LS and ALS circuits. As
this ‘ACT series is used to replace TTL, the Delta ICCT
specification must be considered; this spec may be
confusing and misleading to the engineer unfamiliar with
CMOS.
It is important to understand the concept of Delta ICCT and
how to use it with a design. First, consider where Delta ICCT
initiates. Most CMOS input structures are of the totem pole
type with an n-channel transistor in a series with a p-channel
transistor as illustrated below.
Figure 1–48. CMOS Input Structure
INPUT PAD
VCC
P CHANNEL
N CHANNEL
TO
INTERNAL
LOGIC
These two transistors can be modeled as variable resistors
with resistances varying according to the input voltage. The
resistance of an ON transistor is approximately 50 ohms
while the resistance of an OFF transistor is generally greater
than 5 Mohm. When the input to this structure is at either
ground or VCC, one transistor will be ON and one will be
OFF. The total series resistance of this pair will be the
combination of the two individual resistances, greater than
1
A. When the input is between ground and VCC, the
resistance of the ON transistor will increase while the
resistance of the OFF transistor will decrease. The net
resistance will drop due to the much larger value of the OFF
resistance. The total series resistance can be as low as 600
ohms. This reduction in series resistance of the input
structure will cause a corresponding increase in ICC as
current flows through the input structure. The following
graph depicts typical ICC variance with input voltage for an
‘ACT device.
Figure 1–49. ICC versus Input Voltage for
‘ACT Devices
1.000
0.0000
0.5000 V/DIV
5.000
VIN
0.1000
mA/DIV
ICC
The Delta ICC specification is the increase in ICC. For each
input at VCC–2.1 V, the Delta ICC value should be added to
the quiescent supply current to arrive at the circuit’s
worst-case static ICC value.
Fortunately, there are several factors which tend to reduce
the increase in ICC per input. Most TTL devices will be able
to drive FACT inputs well beyond the TTL output
specification due to FACT’s low input loading in a typical
system. FAST logic outputs can drive ‘ACT-type inputs
down to 200 mV and up to 3.5 V. Additionally, the typical
ICC increase per input will be less than the specified limit. As
shown in the graph above, the ICC increase at VCC–2.1 V is
less than 200
A in the typical system. Experiments have
shown that the ICC of an ‘ACT240 series device typically
increases only 200
A when all of the inputs are connected
to a FAST device instead of ground or VCC.
It is important when designing with FACT, as with any
TTL-compatible CMOS technology, that the Delta ICC
specification be considered. Designers should be aware of
the spec’s significance and that the data book specification
is a worst-case value; most systems will see values that are
much less.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC74AC00DTR2 | 功能描述:逻辑门 2-6V 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 |
| MC74AC00DTR2G | 功能描述:逻辑门 2-6V Quad 2-Input NAND 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 |
| MC74AC00M | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| MC74AC00MEL | 功能描述:逻辑门 2-6V 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 |
| MC74AC00MELG | 功能描述:逻辑门 2-6V Quad 2-Input NAND 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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