參數(shù)資料
型號(hào)： AD7859BSZ
廠商： Analog Devices Inc
文件頁數(shù)： 8/28頁
文件大?。?/td> 0K
描述： IC ADC 12BIT 8CHAN LP 44-MQFP
標(biāo)準(zhǔn)包裝： 1
位數(shù)： 12
采樣率（每秒）： 200k
數(shù)據(jù)接口： 并聯(lián)
轉(zhuǎn)換器數(shù)目： 2
功率耗散（最大）： 30mW
電壓電源： 模擬和數(shù)字
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 44-QFP
供應(yīng)商設(shè)備封裝： 44-MQFP（10x10）
包裝： 托盤
輸入數(shù)目和類型： 8 個(gè)單端，單極；8 個(gè)單端，雙極；4 個(gè)偽差分，單極；4 個(gè)偽差分，雙極
AD7859/AD7859L
REV. A
–16–
Transfer Functions
For the unipolar range the designed code transitions occur mid-
way between successive integer LSB values (i.e., 1/2 LSB,
3/2 LSBs, 5/2 LSBs . . . FS –3/2 LSBs). The output coding is
straight binary for the unipolar range with 1 LSB = FS/4096 =
3.3 V/4096 = 0.8 mV when VREF = 3.3 V. Figure 12 shows the
unipolar analog input configuration. The ideal input/output
transfer characteristic for the unipolar range is shown in
Figure 14.
1LSB =
FS
4096
OUTPUT
CODE
111...111
111...110
111...101
111...100
000...011
000...010
000...001
000...000
0V 1LSB
+FS –1LSB
VIN = (AIN(+) – AIN(–)), INPUT VOLTAGE
Figure 14. AD7859/AD7859L Unipolar Transfer
Characteristic
Figure 13 shows the AD7859/AD7859L’s
±V
REF/2 bipolar ana-
log input configuration. AIN(+) cannot go below 0 ,V so for
the full bipolar range, AIN(–) should be biased to at least
+VREF/2. Once again the designed code transitions occur mid-
way between successive integer LSB values. The output coding
is 2s complement with 1 LSB = 4096 = 3.3 V/4096 = 0.8 mV.
The ideal input/output transfer characteristic is shown in Fig-
ure 15.
1LSB =
FS
4096
FS = VREFV
OUTPUT
CODE
011...111
011...110
000...001
111...111
000...010
000...001
000...000
+FS –1LSB
VIN = (AIN(+) –AIN(–)), INPUT VOLTAGE
000...000
0V
VREF/2
(VREF/2) +1LSB
(VREF/2) –1LSB
Figure 15. AD7859/AD7859L Bipolar Transfer Characteristic
IC1
+3V TO +5V
10k
10k
10k
V+
V–
10k
50
AD820
AD820-3V
VIN
(–VREF/2 TO +VREF/2)
VREF/2
10F
0.1F
10nF
(NPO)
TO AIN(+) OF
AD7854/AD7854L
Figure 11. Analog Input Buffering
Input Ranges
The analog input range for the AD7859/AD7859L is 0 V to
VREF in both the unipolar and bipolar ranges.
The difference between the unipolar range and the bipolar range
is that in the bipolar range the AIN(–) should be biased up to at
least +VREF/2 and the output coding is 2s complement (See
Table VI and Figures 14 and 15).
Table VI. Analog Input Connections
Analog Input
Input Connections
Connection
Range
AIN(+)
AIN(–)
Diagram
0 V to VREF
1
VIN
AGND
Figure 12
±V
REF/2
2
VIN
VREF/2
Figure 13
NOTES
1Output code format is straight binary.
2Range is
±V
REF/2 biased about VREF/2. Output code format is 2s complement.
Note that the AIN(–) channel on the AD7859/AD7859L can be
biased up above AGND in the unipolar mode, or above VREF/2
in bipolar mode if required. The advantage of biasing the lower
end of the analog input range away from AGND is that the ana-
log input does not have to swing all the way down to AGND.
Thus, in single supply applications the input amplifier does not
have to swing all the way down to AGND. The upper end of the
analog input range is shifted up by the same amount. Care must
be taken so that the bias applied does not shift the upper end of
the analog input above the AVDD supply. In the case where the
reference is the supply, AVDD, the AIN(–) should be tied to
AGND in unipolar mode or to AVDD/2 in bipolar mode.
TRACK AND HOLD
AMPLIFIER
AIN(+)
AIN(–)
DB0
DB15
VIN = 0 TO VREF
AD7859/AD7859L
STRAIGHT
BINARY
FORMAT
Figure 12. 0 to VREF Unipolar Input Configuration
TRACK AND HOLD
AMPLIFIER
AIN(+)
AIN(–)
DB0
DB15
VIN = 0 TO VREF
AD7859/AD7859L
2'S
COMPLEMENT
FORMAT
VREF/2
Figure 13.
±V
REF/2 about VREF/2 Bipolar Input Configuration
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD7859L 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V to 5 V Single Supply, 200 kSPS 8-Channel, 12-Bit Sampling ADCs
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AD7859LAS3 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V to 5 V Single Supply, 200 kSPS8-Channel, 12-Bit Sampling ADCs
AD7859LAS-REEL 制造商:Analog Devices 功能描述:ADC Single SAR 100ksps 12-bit Parallel 44-Pin MQFP T/R
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