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參數(shù)資料
| 型號： | AD7859BSZ |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 11/28頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC ADC 12BIT 8CHAN LP 44-MQFP |
| 標準包裝： | 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 |
| 供應商設備封裝： | 44-MQFP（10x10） |
| 包裝： | 托盤 |
| 輸入數(shù)目和類型： | 8 個單端，單極；8 個單端，雙極；4 個偽差分，單極；4 個偽差分，雙極 |
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AD7859/AD7859L
REV. A
–19–
POWER VS. THROUGHPUT RATE
The main advantage of a full power-down after a conversion is
that it significantly reduces the power consumption of the part
at lower throughput rates. When using this mode of operation,
the AD7859/AD7859L is only powered up for the duration of
the conversion. If the power-up time of the AD7859/AD7859L
is taken to be 5
s and it is assumed that the current during
power up is 4.5 mA/1.5 mA typ, then power consumption as a
function of throughput can easily be calculated. The AD7859
has a conversion time of 4.6
s with a 4 MHz external clock and
the AD7859L has a conversion time of 9
s with a 1.8 MHz
clock. This means the AD7859/AD7859L consumes 4.5 mA/
1.5 mA typ for 9.6
s/14 s in every conversion cycle if the parts
are powered down at the end of a conversion. The two graphs,
Figure 24 and Figure 25, show the power consumption of the
AD7859 and AD7859L for VDD = 3 V as a function of through-
put. Table VIII lists the power consumption for various
throughput rates.
Table VIII. Power Consumption vs. Throughput
Power
Throughput Rate
AD7859
AD7859L
1 kSPS
130
W65 W
10 kSPS
1.3 mW
650
W
20 kSPS
2.6 mW
1.25 mW
50 kSPS
6.48 mW
3.2 mW
1.8MHz
OSCILLATOR
AVDD DVDD
AIN(+)
AIN(–)
CREF1
CREF2
SLEEP
DB15
DB0
CONVST
AGND
DGND
CLKIN
REFIN/REFOUT
AD7859L
ANALOG
SUPPLY
+3V
0.1F
10F
0.1F
0.01F
CONVERSION
START SIGNAL
0.1F
CAL
0V TO 2.5V
INPUT
OPTIONAL
EXTERNAL
REFERENCE
CS
RD
WR
W/B
BUSY
DVDD
REF192
CURRENT,
I = 1.5mA TYP
LOW
POWER
C/P
Figure 23. Typical Low Power Circuit
CONVST
BUSY
5s
4.6s
tCONVERT
START CONVERSION ON RISING EDGE
POWER UP ON FALLING EDGE
POWER-UP
TIME
NORMAL
OPERATION
FULL
POWER-DOWN
POWER-UP
TIME
Figure 21. Using the CONVST Pin to Power Up the AD7859
for a Conversion
Using The Internal (On-Chip) Reference
As in the case of an external reference, the AD7859/AD7859L
can power up from one of two conditions, power-up after the
supplies are connected or power-up from hardware/software
power-down.
When using the on-chip reference and powering up when AVDD
and DVDD are first connected, it is recommended that the
power-up calibration mode be disabled as explained above.
When using the on-chip reference, the power-up time is effec-
tively the time it takes to charge up the external capacitor on the
REFIN/REFOUT pin. This time is given by the equation:
tUP = 9
× R × C
where R
≈ 150K and C = external capacitor.
The recommended value of the external capacitor is 100 nF;
this gives a power-up time of approximately 135 ms before a
calibration is initiated and normal operation should commence.
When CREF is fully charged, the power-up time from a hardware
or software power-down reduces to 5
s. This is because an in-
ternal switch opens to provide a high impedance discharge path
for the reference capacitor during power-down—see Figure 22.
An added advantage of the low charge leakage from the refer-
ence capacitor during power-down is that even though the refer-
ence is being powered down between conversions, the reference
capacitor holds the reference voltage to within 0.5 LSBs with
throughput rates of 100 samples/second and over with a full
power-down between conversions. A high input impedance op
amp like the AD707 should be used to buffer this reference
capacitor if it is being used externally. Note, if the AD7859/
AD7859L is left in its powered-down state for more than
100 ms, the charge on CREF will start to leak away and the
power-up time will increase. If this long power-up time is a
problem, the user can use a partial power-down for the last con-
version so the reference remains powered up.
BUF
ON-CHIP
REFERENCE
TO OTHER
CIRCUITRY
SWITCH OPENS
DURING POWER-DOWN
REFIN/OUT
EXTERNAL
CAPACITOR
Figure 22. On-Chip Reference During Power-Down
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相關代理商/技術參數(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 |
| AD7859LAS | 制造商:Analog Devices 功能描述:ADC Single SAR 100ksps 12-bit Parallel 44-Pin MQFP 制造商:Rochester Electronics LLC 功能描述:12-BIT 8 CH.PARALLEL 100 KSPS I.C. - Bulk 制造商:Analog Devices 功能描述:IC 12-BIT ADC |
| 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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