參數(shù)資料
型號(hào)： ADS8422IPFBT
英文描述： 16-BIT, 4-MSPS, PSEUDO-BIPOLAR, FULLY DIFFERENTIAL INPUT, MICROPOWER SAMPLING ANALOG-TO-DIGITAL CONVERTER WITH PARALLEL INTERFACE, REFERENCE
中文描述： 16位4 MSPS的，偽雙極，全差分輸入，微采樣模擬到數(shù)字轉(zhuǎn)換并行接口，參考
文件頁(yè)數(shù)： 21/25頁(yè)
文件大?。?/td> 816K
代理商： ADS8422IPFBT
www.ti.com
LAYOUT
For optimum performance, care should be taken with the physical layout of the ADS8422 circuitry.
ADS8422
SLAS512B–JUNE 2006–REVISED DECEMBER 2006
ADC powerdown is activated by asserting PD1 to 0 for longer than 1.5
μ
s. If the signal PD1 is asserted 0 for
less than 0.5
μ
s, the ADC is only reset and any ongoing conversion aborted. See
Figure 26
. ADC operation can
be resumed from ADC powerdown by de-asserting the PD1 pin. In ADC power-down mode, the analog outputs
from the ADC(COMMOUT, REFOUT) are not powered down thereby reducing the power-on time.
Full chip power-down is activated by turning off the power supply or by asserting both, PD1 = 0 and PD2 = 0 for
longer than 1.5
μ
s (see
Figure 27
). In this mode, even the analog outputs of the ADC (COMMOUT, REFOUT)
are powered down thereby giving maximum power saving. Device operation can be resumed from full chip
power-down by turning on the power supply or by deasserting both, PD1 = 1 and PD2 = 1.
Table 3. Effects of RESET, PD1, and PD2
COMMAND
RESET/PD1 = 0
PD1 = 0, PD2 = 1
PD1 = PD2 = 0
PD1 = 1, PD2 = 0
APPLICATION TIME
20 ns
1.5
μ
s
1.5
μ
s
POWER WHEN APPLIED
No change
17mW
40
μ
W
Reserved – Do not use this combination
RESUME TIME
20 ns
5
μ
s
25 ms
As the ADS8422 offers single-supply operation, it is often used in close proximity with digital logic,
microcontrollers, microprocessors, and digital signal processors. The more digital logic present in the design and
the higher the switching speed, the more difficult it is to achieve good performance from the converter.
The basic SAR architecture is sensitive to glitches or sudden changes on the power supply, reference, ground
connections, and digital inputs that occur just prior to latching the output of the analog comparator. Thus, driving
any single conversion for an n-clock SAR converter, there are n
windows
in which large external transient
voltages can affect the conversion result. Such glitches might originate from switching power supplies, nearby
digital logic, or high power devices. The 50 ns period before BUSY falls should be kept free of supply glitches.
The degree of error in the digital output depends on the reference voltage, layout, and the exact timing of the
external event.
On average, the ADS8422 draws very little current from an external reference as the reference voltage is
internally buffered. If the reference voltage is external and originates from an op amp, make sure that it can drive
the bypass capacitor or capacitors without oscillation. A 0.1-
μ
F bypass capacitor is recommended from pin 1
directly to REFM (pin 48). REFM and AGND should be shorted on the same ground plane underneath the
device.
The AGND, BDGND, and AGND pins should be connected to a clean ground point. In all cases, this should be
the
analog
ground. Avoid connections which are too close to the grounding point of a microcontroller or digital
signal processor. If required, run a ground trace directly from the converter to the power supply entry point. The
ideal layout consists of an analog ground plane dedicated to the converter and associated analog circuitry.
As with the AGND connections, +VA and +VAREG should be connected to their respective power supply planes
or traces that are separate from the connection for digital logic, until they are connected at the power entry point.
Power to the ADS8422 should be clean and well bypassed. A 0.1-
μ
F ceramic bypass capacitor should be placed
as close to the device as possible. See
Table 4
for capacitor placement. In addition, a 1-
μ
F to 10-
μ
F capacitor is
recommended. In some situations, additional bypassing may be required, such as a 100-
μ
F electrolytic capacitor
or even a
Pi
filter made up of inductors and capacitors — all designed to essentially low-pass filter the +5-V
supply, thus removing the high frequency noise.
Table 4. Power Supply Decoupling Capacitor Placement
POWER SUPPLY PLANE
SUPPLY PINS
CONVERTER
DIGITAL SIDE
CONVERTER ANALOG SIDE
Pin pairs that require shortest path to decoupling capacitors
(4,5), (9,8), (10,12), (13,15), (43,44), (46,45)
(24,25), (34,35)
21
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ADS8471 制造商:BB 制造商全稱:BB 功能描述:16-BIT, 1-MSPS, PSEUDO-BIPOLAR, FULLY DIFFERENTIAL INPUT, MICROPOWER SAMPLING ANALOG-TO-DIGITAL CONVERTER WITH PARALLEL INTERFACE, REFERENCE
ADS8471IBRGZR 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 16B 1MSPS Psuedo- Diff SAR ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
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ADS8471IBRGZT 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 16B 1MSPS Psuedo- Diff SAR ADC W/ Ref RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
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