HI5805 데이터 시트보기 (PDF) - Renesas Electronics
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HI5805 Datasheet PDF : 12 Pages
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HI5805
TABLE 1.
CODE CENTER
DESCRIPTION
DIFFERENTIAL
INPUT VOLTAGE† MSB
(USING INTERNAL
REFERENCE)
D11 D10 D9
OFFSET BINARY OUTPUT CODE
LSB
D8 D7 D6 D5 D4 D3 D2 D1 D0
+Full Scale (+FS) - 1/4 LSB +1.99976V
1
1
1
1
1
1
1
1
1
1
1
1
+FS - 11/4 LSB
1.99878V
1
1
1
1
1
1
1
1
1
1
1
0
+ 3/4 LSB
732.4V
1
0
0
0
0
0
0
0
0
0
0
0
- 1/4 LSB
-244.1V
0
1
1
1
1
1
1
1
1
1
1
1
-FS + 13/4 LSB
-1.99829V
0
0
0
0
0
0
0
0
0
0
0
1
-Full Scale (-FS) + 3/4 LSB -1.99927V
0
0
0
0
0
0
0
0
0
0
0
0
† The voltages listed above represent the ideal center of each offset binary output code shown.
Analog Input, Differential Connection
The analog input to the HI5805 can be configured in various
ways depending on the signal source and the required level of
performance. A fully differential connection (Figure 15) will give
the best performance for the converter.
VIN
VIN+
HI5805
VDC
-VIN
VIN-
FIGURE 15. AC COUPLED DIFFERENTIAL INPUT
Since the HI5805 is powered off a single +5V supply, the
analog input must be biased so it lies within the analog input
common mode voltage range of 1.0V to 4.0V. The
performance of the ADC does not change significantly with the
value of the analog input common mode voltage.
A 2.3V DC bias voltage source, VDC, half way between the top
and bottom internal reference voltages, is made available to
the user to help simplify circuit design when using a differential
input. This low output impedance voltage source is not
designed to be a reference but makes an excellent bias source
and stays within the analog input common mode voltage range
over temperature.
The difference between the converter’s two internal voltage
references is 2V. For the AC coupled differential input,
(Figure 15), if VIN is a 2VP-P sinewave with -VIN being 180
degrees out of phase with VIN , then VIN+ is a 2VP-P
sinewave riding on a DC bias voltage equal to VDC and VIN-
is a 2VP-P sinewave riding on a DC bias voltage equal to
VDC . Consequently, the converter will be at positive full
scale, all 1s digital data output code, when the VIN+ input is
at VDC +1V and the VIN- input is at VDC -1V (VIN+ - VIN- =
2V). Conversely, the ADC will be at negative full scale, all 0s
digital data output code, when the VIN+ input is equal to VDC-
1V and VIN- is at VDC +1V (VIN+ - VIN- = -2V). From this, the
converter is seen to have a peak-to-peak differential analog
input voltage range of 2V.
The analog input can be DC coupled (Figure 16) as long as the
inputs are within the analog input common mode voltage range
(1.0V VDC 4.0V).
VIN
VDC
VDC
-VIN
VIN+
R
C
HI5805
VDC
R
VIN-
FIGURE 16. DC COUPLED DIFFERENTIAL INPUT
The resistors, R, in Figure 16 are not absolutely necessary but
may be used as load setting resistors. A capacitor, C,
connected from VIN+ to VIN- will help filter any high frequency
noise on the inputs, also improving performance. Values
around 20pF are sufficient and can be used on AC coupled
inputs as well. Note, however, that the value of capacitor C
chosen must take into account the highest frequency
component of the analog input signal.
Analog Input, Single-Ended Connection
The configuration shown in Figure 17 may be used with a
single ended AC coupled input. Sufficient headroom must be
provided such that the input voltage never goes above +5V or
below AGND.
FN3984 Rev 7.00
March 31, 2005
Page 9 of 12
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