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參數(shù)資料
| 型號： | ZN449 |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | TV 53C 40#22D 9#16 4#12 PIN RE |
| 中文描述： | 8位微處理器兼容AD轉換器 |
| 文件頁數(shù)： | 5/18頁 |
| 文件大?。?/td> | 289K |
| 代理商： | ZN449 |
ZN448/9
5
If a free-running conversion is required, then the converter can
be made to cycle by inverting the
BUSY
output and feeding it
to
WR
. To ensure that the converter starts reliably after power-
up an initial start pulse is required. This can be ensured by
using a NOR gate instead of an inverter and feeding it with a
positive-going pulse which can be derived from a simple RC
network that gives a single pulse when power is applied, as
shown in Fig.4a.
The ADC will complete a conversion on every eighth clock
pulse, with the
BUSY
output going high for a period
determined by the propagation delay of the NOR gate, during
which time the data can be stored in a latch. The time available
for storing data can be increased by inserting delays into the
inverter path.
A timing diagram for the continuous conversion mode is
shown in Fig.3b.
As the
BUSY
output uses a passive pull-up the rise time of this
output depends on the RC time constant of the pull-up resistor
and load capacitance. In the continuous conversion mode the
use of a 4k7 external pull-up resistor is recommended to
reduce the risetime and ensure that a logic 1 level is reached.
Fig.4b Timing for continuous conversion
DATA OUTPUTS
The data outputs are provided with three-state buffers to allow
connection to a common data bus. An equivalent circuit is
shown in Fig.5. Whilst the
RD
input is high both output
transistors are turned off and the ZN448/9 presents only a high
impedance load to the bus.
When
RD
is low the data outputs will assume the logic states
present at the outputs of the successive register.
A test circuit and timing diagram for the output enable/disable
delays are given in Fig.6.
Fig.4a Circuit for continuous conversion
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ZN449D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-BIT MICROPROCESSOR COMPATIBLE A-D CONVERTER |
| ZN449E | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-BIT MICROPROCESSOR COMPATIBLE A-D CONVERTER |
| ZN449J | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Converter IC |
| ZN450CJ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:VOLTMETER CIRCUIT|DIP|40PIN|CERAMIC |
| ZN450E | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Converter IC |
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