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參數(shù)資料
| 型號： | AD7859BS |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 3 V to 5 V Single Supply, 200 kSPS 8-Channel, 12-Bit Sampling ADCs |
| 中文描述： | 8-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PQFP44 |
| 封裝： | PLASTIC, QFP-44 |
| 文件頁數(shù)： | 19/28頁 |
| 文件大小： | 535K |
| 代理商： | AD7859BS |
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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
μ
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
μ
s with a 4 MHz external clock and
the AD7859L has a conversion time of 9
μ
s with a 1.8 MHz
clock. This means the AD7859/AD7859L consumes 4.5 mA/
1.5 mA typ for 9.6
μ
s/14
μ
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 V
DD
= 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
AD7859
Power
AD7859L
Throughput Rate
1 kSPS
10 kSPS
20 kSPS
50 kSPS
130
μ
W
1.3 mW
2.6 mW
6.48 mW
65
μ
W
650
μ
W
1.25 mW
3.2 mW
1.8MHz
OSCILLATOR
AV
DD
DV
DD
AIN(+)
AIN(–)
C
REF1
C
REF2
SLEEP
DB15
DB0
CONVST
AGND
DGND
CLKIN
REF
IN
/REF
OUT
AD7859L
ANALOG
SUPPLY
+3V
0.1μF
0.1μF
10μF
0.1μF
0.01μF
CONVERSION
START SIGNAL
0.1μF
CAL
0V TO 2.5V
INPUT
OPTIONAL
EXTERNAL
REFERENCE
CS
RD
WR
W/B
BUSY
DV
DD
REF192
CURRENT,
I = 1.5mA TYP
LOW
POWER
μC/μP
Figure 23. Typical Low Power Circuit
CONVST
BUSY
5μs
4.6μs
t
CONVERT
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 AV
DD
and DV
DD
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
REF
IN
/REF
OUT
pin. This time is given by the equation:
t
UP
= 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 C
REF
is fully charged, the power-up time from a hardware
or software power-down reduces to 5
μ
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 C
REF
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
REF
IN/OUT
EXTERNAL
CAPACITOR
Figure 22. On-Chip Reference During Power-Down
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD7859L* | 5V Low Power RS232 Transceiver; Package: PDIP; No of Pins: 16; Temperature Range: 0°C to +70°C |
| AD7859LAS | 3 V to 5 V Single Supply, 200 kSPS 8-Channel, 12-Bit Sampling ADCs |
| AD7859L | 3 V to 5 V Single Supply, 200 kSPS 8-Channel, 12-Bit Sampling ADCs(單電源,200kSPS 8通道12位采樣A/D轉(zhuǎn)換器) |
| AD7859 | 3 V to 5 V Single Supply, 200 kSPS 8-Channel, 12-Bit Sampling ADCs(單電源,200kSPS 8通道12位采樣A/D轉(zhuǎn)換器) |
| AD7861AP | 11-Bit Resolution Simultaneous Sampling A/D Converter |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7859BSZ | 功能描述:IC ADC 12BIT 8CHAN LP 44-MQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1,000 系列:- 位數(shù):12 采樣率（每秒）:300k 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:75mW 電壓電源:單電源 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:24-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:24-SOIC 包裝:帶卷 (TR) 輸入數(shù)目和類型:1 個單端，單極；1 個單端，雙極 |
| 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 |
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