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參數(shù)資料
| 型號(hào)： | ADS7835 |
| 英文描述： | 12-Bit, High-Speed, Low Power Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 12位，高速，低功耗采樣模擬到數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 9/13頁 |
| 文件大?。?/td> | 169K |
| 代理商： | ADS7835 |
9
ADS7835
clock cycle is the first of the conversion.)
In addition, if CONV is completely asynchronous to CLK
and CLK is continuous, there is the possibility that CLK will
transition just prior to CONV going LOW. If this occurs
faster than the 10ns indicated by t
CKCH
, there is a chance that
some digital feedthrough may be coupled onto the hold
capacitor. This could cause a small offset error for that
particular conversion.
Thus, there are two basic ways to operate the ADS7835.
CONV can be synchronous to CLK and CLK can be con-
tinuous. This would be the typical situation when interfacing
the converter to a digital signal processor. The second
method involves having CONV asynchronous to CLK and
gating the operation of CLK (a non-continuous clock). This
method would be more typical of an SPI-like interface on a
microcontroller. This method would also allow CONV to be
generated by a trigger circuit and to initiate (after some
delay) the start of CLK. These two methods are covered
under the DSP Interfacing and SPI Interfacing sections of
this data sheet.
POWER-DOWN TIMING
The conversion timing shown in Figure 3 does not result in
the ADS7835 going into the power-down mode. If the
conversion rate of the device is high (approaching 500kHz),
there is very little power that can be saved by using the
power-down mode. However, since the power-down mode
incurs no conversion penalty (the very first conversion is
valid) at lower sample rates, significant power can be saved
by allowing the device to go into power-down mode be-
tween conversions.
Figure 4 shows the typical method for placing the A/D into
the power-down mode. If CONV is kept LOW during the
conversion and is LOW at the start of the 13th clock cycle,
the device enters the power-down mode. It remains in this
mode until the rising edge of CONV. Note that CONV must
be HIGH for at least t
ACQ
in order to sample the signal
properly as well as to power-up the internal nodes.
There are two different methods for clocking the ADS7835.
The first involves scaling the CLK input in relation to the
conversion rate. For example, an 8MHz input clock and the
timing shown in Figure 3 results in a 500kHz conversion
rate. Likewise, a 1.6MHz clock would result in a 100kHz
conversion rate. The second method involves keeping the
clock input as close to the maximum clock rate as possible
and starting conversions as needed. This timing is similar to
that shown in Figure 4. As an example, a 50kHz conversion
rate would require 160 clock periods per conversion instead
of the 16 clock periods used at 500kHz.
The main distinction between the two is the amount of time
that the ADS7835 remains in power-down. In the first mode,
the converter only remains in power-down for a small
number of clock periods (depending on how many clock
periods there are per each conversion). As the conversion
rate scales, the converter always spends the same percentage
of time in power-down. Since less power is drawn by the
digital logic, there is a small decrease in power consump-
tion, but it is very slight. This effect can be seen in the
FIGURE 3. Basic Conversion Timing.
D11
(MSB)
DATA
NOTES: (1) Clock periods 14 and 15 are shown for clarity, but are not required for proper operation of the ADS7835, provided that the
minimum t
time is met. The CLK input may remain HIGH or LOW during this period. (2) The transition from sample mode to hold
mode occurs on the falling edge of CONV. This transition is not dependent on CLK. (3) The device remains fully powered when
operated as shown. If the sample time is longer than 3 clock periods, power consumption can be reduced by allowing the device to
enter a power-down mode. See the Power-Down Timing section for more information.
HOLD
CONVERSION IN PROGRESS
IDLE
IDLE(3)
SAMPLE
SAMPLE
(2)
(1)
HOLD
CLK
1
2
3
4
11
12
13
14
15
14
15
16
16
1
CONV
SAMPLE/HOLD
MODE
INTERNAL
CONVERSION
STATE
D10
D9
D2
D1
D0
(LSB)
t
CKDE
t
CVHD
t
CONV
t
ACQ
t
CKCS
t
CKCH
t
CKSP
t
CVL
t
CKDD
t
CVCK
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS7835E | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ADS7835E/250 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit High Speed Low Power Sampling 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 |
| ADS7835E/250G4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit High Speed Low Power Sampling 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 |
| ADS7835E/2K5 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit High Speed Low Power Sampling 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 |
| ADS7835E/2K5G4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit High Speed Low Power Sampling 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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