SP8510KN データシートの表示（PDF） - Signal Processing Technologies

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SP8510KN

12-Bit Sampling A/D Converters

Signal Processing Technologies 

FEATURES...

The SP85XX Series are specified at sampling

rates of 333kHz (SP8503), 200kHz (SP8505) or

100kHz (SP8510). Conversion times are factory

set for 2.70µs, 4.7µs and 9.7µs maximum, re-

spectively, over temperature, and the high-

speed sampling input stage insures a total acqui-

sition and conversion time of 3µs, 5µs and 10µs

maximum, respectively, over temperature. Pre-

cision, laser-trimmed scaling resistors provide

industry–standard input ranges of ±5V or ±10V.

The 28-pin SP85XX Series are available in

narrow body plastic DIP, and SOIC packages

and it operates from a single +5V supply.

The SP85XX Series are available in grades

specified over the 0°C to +70°C commercial

temperature ranges.

OPERATION

Basic Operation

Figure 1 shows the simple hookup circuit required

to operate the SP85XX Series in a ±10V range in

the Convert Mode. A convert command arriving

on R/C puts the SP85XX Series in the HOLD

mode, and a conversion is started. This pulse must

be LOW for a minimum of 40ns. Because this

pulse establishes the sampling instant of the A/D,

it must have very low jitter. BUSY will be held

LOW during the conversion, and rises only after

the conversion is completed and the data has been

transferred to the output drivers. Thus, the rising

Input

1 N.C.

2 IN 1

3 IN 2

N.C. 28

+5V

+5V 27

+5V 26

6.8µF +

0.1µF

4 VREF

N.C. 25

5 AGND BUSY 24

6 D11 (MSB) CS 23

Busy

7 D10

8 D9

R/C 22

HBE 21

Convert

Command

9 D8 D0 (LSB) 20

10 D7

D1 19

11 D6

D2 18

12 D5

D3 17

D11

(MSB)

13 D4

14 N.C.

DGND 16

N.C. 15

Data

Out

D0

(LSB)

Figure 1. Basic ±10V Operation

edge can be used to read the data from the conver-

sion. Also, during conversion, the BUSY signal

puts the output data lines in Hi-Z states and inhibits

the input lines. This means that pulses on R/C are

ignored, so that new conversions cannot be initi-

ated during a conversion, either as a result of

spurious signals or to short-cycle the SP85XX

Series.

In the Read Mode, the input to R/C is kept nor-

mally LOW, and a HIGH pulse is used to read data

and initiate a conversion. In this mode, the rising

edge of R/C will enable the output data pins, and

the data from the previous conversion becomes

valid. The falling edge then puts the SP85XX

Series in a hold mode, and initiates a new conver-

sion.

The SP85XX Series will begin acquiring a new

sample just prior to the BUSY output rising, and

will track the input signal until the next conversion

is started.

For use with an 8-bit bus, the data can be read out in two

bytes under the control of HBE. With a LOW input

on HBE, at the end of a conversion, the 8 LSBs of data

are loaded into the output drivers on D7 through D4 and

D3 through D0. Taking HBE HIGH then loads the 4

MSBs on D3 through D0, with D7 through D4 being

forced LOW.

Analog Input Ranges

The SP85XX Series offers two standard bipolar

input ranges: ±10V and ±5V. If a ±10V range is

required, the analog input signal should be con-

nected to pin 2. A signal requiring a ±5V range

should be connected to pin 3. In either case, the

other pin of the two must be grounded or connected

to the adjustment circuits described in the section

on calibration.

Controlling The SP85XX Series

The SP85XX Series can be easily interfaced to most

microprocessor-based and other digital systems. The

microprocessor may take full control of each conver-

sion, or the SP85XX Series may operate in a stand-

alone mode, controlled only by the R/C input. Full

control consists of initiating the conversion and read-

ing the output data at user command, transmitting data

either all 12-bits in one parallel word, or in two 8-bit

bytes. The three control inputs (CS, R/C and HBE) are

47

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