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零件编号 | ADC0805 | ||
描述 | 8-Bit uP Compatible A/D Converters | ||
制造商 | National Semiconductor | ||
LOGO | |||
1 Page
November 1999
ADC0801/ADC0802/ADC0803/ADC0804/ADC0805
8-Bit µP Compatible A/D Converters
General Description
The ADC0801, ADC0802, ADC0803, ADC0804 and
ADC0805 are CMOS 8-bit successive approximation A/D
converters that use a differential potentiometric
ladder — similar to the 256R products. These converters are
designed to allow operation with the NSC800 and INS8080A
derivative control bus with TRI-STATE® output latches di-
rectly driving the data bus. These A/Ds appear like memory
locations or I/O ports to the microprocessor and no interfac-
ing logic is needed.
Differential analog voltage inputs allow increasing the
common-mode rejection and offsetting the analog zero input
voltage value. In addition, the voltage reference input can be
adjusted to allow encoding any smaller analog voltage span
to the full 8 bits of resolution.
Features
n Compatible with 8080 µP derivatives — no interfacing
logic needed - access time - 135 ns
n Easy interface to all microprocessors, or operates “stand
alone”
n Differential analog voltage inputs
n Logic inputs and outputs meet both MOS and TTL
voltage level specifications
n Works with 2.5V (LM336) voltage reference
n On-chip clock generator
n 0V to 5V analog input voltage range with single 5V
supply
n No zero adjust required
n 0.3" standard width 20-pin DIP package
n 20-pin molded chip carrier or small outline package
n Operates ratiometrically or with 5 VDC, 2.5 VDC, or
analog span adjusted voltage reference
Key Specifications
n Resolution
n Total error
n Conversion time
8 bits
±1⁄4 LSB, ±1⁄2 LSB and ±1 LSB
100 µs
Connection Diagram
ADC080X
Dual-In-Line and Small Outline (SO) Packages
Ordering Information
TEMP RANGE
±1⁄4 Bit Adjusted
ERROR
±1⁄2 Bit Unadjusted
±1⁄2 Bit Adjusted
±1Bit Unadjusted
PACKAGE OUTLINE
DS005671-30
See Ordering Information
0˚C TO 70˚C
ADC0802LCWM
ADC0804LCWM
M20B — Small
Outline
0˚C TO 70˚C
−40˚C TO +85˚C
ADC0801LCN
ADC0802LCN
ADC0803LCN
ADC0804LCN
ADC0805LCN/ADC0804LCJ
N20A — Molded DIP
TRI-STATE® is a registered trademark of National Semiconductor Corp.
Z-80® is a registered trademark of Zilog Corp.
© 1999 National Semiconductor Corporation DS005671
www.national.com
Typical Applications (Continued)
Absolute with a 2.500V Reference
Absolute with a 5V Reference
*For low power, see also LM385–2.5
DS005671-55
Zero-Shift and Span Adjust: 2V ≤ VIN ≤ 5V
DS005671-56
Span Adjust: 0V ≤ VIN ≤ 3V
DS005671-57
DS005671-58
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Typical Applications (Continued)
Sampling an AC Input Signal
DS005671-78
Note 11: Oversample whenever possible [keep fs > 2f(−60)] to eliminate input frequency folding (aliasing) and to allow for the skirt response of the filter.
Note 12: Consider the amplitude errors which are introduced within the passband of the filter.
70% Power Savings by Clock Gating
(Complete shutdown takes ≈ 30 seconds.)
DS005671-79
Power Savings by A/D and VREF Shutdown
*Use ADC0801, 02, 03 or 05 for lowest power consumption.
Note: Logic inputs can be driven to VCC with A/D supply at zero volts.
Buffer prevents data bus from overdriving output of A/D when in shutdown mode.
Functional Description
1.0 UNDERSTANDING A/D ERROR SPECS
A perfect A/D transfer characteristic (staircase waveform) is
shown in Figure 1. The horizontal scale is analog input volt-
age and the particular points labeled are in steps of 1 LSB
(19.53 mV with 2.5V tied to the VREF/2 pin). The digital out-
put codes that correspond to these inputs are shown as D−1,
D, and D+1. For the perfect A/D, not only will center-value
DS005671-80
(A−1, A, A+1, . . . . ) analog inputs produce the correct out-
put digital codes, but also each riser (the transitions between
adjacent output codes) will be located ±1⁄2 LSB away from
each center-value. As shown, the risers are ideal and have
no width. Correct digital output codes will be provided for a
range of analog input voltages that extend ±1⁄2 LSB from the
ideal center-values. Each tread (the range of analog input
voltage that provides the same digital output code) is there-
fore 1 LSB wide.
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页数 | 30 页 | ||
下载 | [ ADC0805.PDF 数据手册 ] |
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