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參數(shù)資料
| 型號： | HI3-7159A-5Z |
| 廠商： | Intersil |
| 文件頁數(shù)： | 3/14頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC ADC 5-1/2 DIGIT 28-PDIP |
| 標準包裝： | 13 |
| 位數(shù)： | 5.5 位 |
| 采樣率（每秒）： | 200k |
| 數(shù)據(jù)接口： | 串行，并聯(lián) |
| 轉(zhuǎn)換器數(shù)目： | 1 |
| 電壓電源： | 單電源 |
| 工作溫度： | 0°C ~ 70°C |
| 安裝類型： | 通孔 |
| 封裝/外殼： | 28-DIP（0.600"，15.24mm） |
| 供應(yīng)商設(shè)備封裝： | 28-PDIP |
| 包裝： | 管件 |
| 輸入數(shù)目和類型： | 1 個差分，雙極 |
11
It may also be possible to directly program the host’s serial
hardware for operation at nonstandard baud rates, allowing
HI-7159A operation at any arbitrary frequency. For example:
50Hz AC rejection requires a 2MHz clock. At this frequency
the “9600” baud rate becomes 7812.5 baud. The host’s
UART must be programmed with the proper divider to
operate at this baud rate. The data clock (see Figure 2) is
dened as 16 times the baud rate, so the data clock of this
conguration would be 125kHz. The data clock can also be
determined by dividing the oscillator (clock) frequency by the
correct divider from Table 12.
The following equation determines the divider needed to
operate the HI-7159A at any given crystal frequency:
Once determined, the new divider must be written directly to
the Host’s UART. Most PC compatibles use an 8250 UART with
a 1.8432MHz crystal, so the proper divider for the 2MHz
example given above would be 15. Again, these considerations
apply only to Serial Modes 1 and 2. Parallel and Serial Mode 0
communication rates are independent of crystal frequency.
Conversion Time
The conversion time of the HI-7159A is a function of the
crystal frequency and the type of conversion being made.
The conversion times for fCLOCK = 2.4MHz are shown in
Table 13. At other clock frequencies the times may be
calculated from the following formula:
where the constant C is determined from Table 13.
Component Selection
Three external passive components must be chosen for the
HI-7159A: the integrating capacitor (CINT), the integrating
resistor (RINT), and the reference capacitor (CREF). They are
chosen based on the crystal frequency, the reference voltage
(VREF), and the desired integrating current. Figure 8 illustrates
the analog components necessary for the HI-7159A to function.
The reference capacitor and integrating components can
either be selected from Table 14, or calculated from the
following equations.
CREF acts as a voltage source at different times during a
conversion. Its value is determined by two considerations: it
must be small enough to be fully charged from its
discharged state at power-on; yet it also must be large
enough to supply current to the circuit during conversion
without significantly drooping from its initial value. For
2.4MHz operation, a 1
F capacitor is recommended. The
equation for other frequencies is:
The values of RINT and CINT are selected by choosing the
maximum integration current and the maximum integrator
output voltage swing. The maximum integration current and
voltage swing occurs when VIN = full scale = 2 X VREF. The
recommended integration current for the HI-7159A is
5mA - 10mA. This will help determine the value of RINT,
since:
where VIN = VIN HI - VIN LO = 2 x VREF.
TABLE 12. CRYSTAL DIVIDER RATIOS
BAUD RATE SELECTED
CRYSTAL DIVIDER
“300”
512
“1200”
128
“9600”
16
“19200”
8
TABLE 13. CONVERSION TIMES
CONVERSION TYPE
51/2
COMP
51/2
UNCOMP
41/2
COMP
41/2
UNCOMP
f = 2.4MHz
133ms
66.7ms
33.3ms
16.7ms
C
320,000
160,000
80,000
40,000
f
CLOCK 7159A
()
Divider 7159A
()
--------------------------------------------
f
CRYSTAL Host UART
()
Divider Host UART
()
----------------------------------------------------------------
Data Clock
==
t
CONV
C
f
CLOCK
---------------------
=
TABLE 14. RECOMMENDED COMPONENT VALUES vs
CLOCK FREQUENCY
fCLOCK
RINT
CINT
CREF
2.4MHz
400k
0.01
F
1.0
F
1.2MHz
360k
0.022
F
2.2
F
600kHz
330k
0.047
F
4.7
F
NOTE: CINT MUST be a high quality polypropylene capacitor or
performance may be degraded.
+5V
27
1
VCC
VEE
14
AGND
INT OUT
INT IN
BUF OUT
DGND
RINT
CINT
CREF-
CREF+
CREF
CREF+ GUARD
2
3
4
5
6
7
8
9
12
13
11
10
26
REFERENCE
CAPACITOR
GUARD
RINGS
DGND
AGND
VREF HI
REF LO
VIN HI
VIN LO
-5V
HI-7159A
CREF - GUARD
FIGURE 8. ANALOG COMPONENTS AND INPUTS
XTAL
C
REF
2.5
f
CLOCK
---------------------
=
I
INT
V
IN
R
INT
-------------
so
R
INT
V
IN
I
INT
-----------
,
==
HI-7159A
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