參數(shù)資料
型號(hào)： EVAL-AD7715-5EB
廠商： Analog Devices, Inc.
英文描述： 3 V/5 V, 450 uA 16-Bit, Sigma-Delta ADC
中文描述： 3伏/ 5伏，450微安16位Σ-Δ模數(shù)轉(zhuǎn)換器
文件頁(yè)數(shù)： 15/31頁(yè)
文件大小： 474K
代理商： EVAL-AD7715-5EB
AD7715
–15–
REV. C
C
SAMP
must be charged through R
SW
and through any external
source impedances every input sample cycle. Therefore, in
unbuffered mode, source impedances mean a longer charge time
for C
SAMP
, and this may result in gain errors on the part. Table
XIV shows the allowable external resistance/capacitance values,
for unbuffered mode, such that no gain error to the 16-bit level
is introduced on the part. Note that these capacitances are total
capacitances on the analog input, external capacitance plus
10 pF capacitance from the pins and lead frame of the device.
Table XIV. External R, C Combination for No 16-Bit Gain
Error (Unbuffered Mode Only)
Gain
External Capacitance (pF)
10
152 k
53.9 k
31.4 k
8.4 k
75.1 k
26.6 k
15.4 k
4.14 k
2.36 k
670
16.7 k
5.95 k
3.46 k
924
16.7 k
5.95 k
3.46 k
924
50
100
500
1000
4.76 k
1.36 k
5000
1
2
32
128
526
526
150
150
In buffered mode, the analog inputs look into the high imped-
ance inputs stage of the on-chip buffer amplifier. C
SAMP
is
charged via this buffer amplifier such that source impedances do
not affect the charging of C
SAMP
. This buffer amplifier has an
offset leakage current of 1 nA. In this buffered mode, large
source impedances result in a small dc offset voltage developed
across the source impedance but not in a gain error.
Input Sample Rate
The modulator sample frequency for the AD7715 remains at
f
CLKIN
/128 (19.2kHz @ f
CLK IN
= 2.4576MHz) regardless of
the selected gain. However, gains greater than 1 are achieved by
a combination of multiple input samples per modulator cycle
and a scaling of the ratio of reference capacitor to input capaci-
tor. As a result of the multiple sampling, the input sample rate
of the device varies with the selected gain (see Table XV). In
buffered mode, the input is buffered before the input sampling
Table XV. Input Sampling Frequency vs. Gain
Gain
Input Sampling Freq (f
S
)
f
CLK IN
/64 (38.4kHz @ f
CLK IN
= 2.4576MHz)
2
f
CLK IN
/64 (76.8kHz @ f
CLK IN
= 2.4576MHz)
8
×
f
CLK IN
/64 (307.2kHz @ f
CLK IN
= 2.4576MHz)
8
×
f
CLK IN
/64 (307.2kHz @ f
CLK IN
= 2.4576MHz)
capacitor. In unbuffered mode, where the analog input looks
directly into the sampling capacitor, the effective input imped-
ance is 1/C
SAMP
×
f
S
where C
SAMP
is the input sampling capaci-
tance and f
S
is the input sample rate.
Bipolar/Unipolar Inputs
The analog input on the AD7715 can accept either unipolar or
bipolar input voltage ranges. Bipolar input ranges do not imply
that the part can handle negative voltages on its analog input
since the analog input cannot go more negative than –30mV to
ensure correct operation of the part. The input channel is fully
differential. As a result, the voltage to which the unipolar and
bipolar signals on the AIN(+) input are referenced is the voltage
on the respective AIN(–) input. For example, if AIN(–) is
+2.5V and the AD7715 is configured for unipolar operation
1
2
32
128
SCLK
MCLK IN
DGND
DV
DD
MCLK OUT
DIN
DOUT
AGND
AIN(+)
AIN(–)
REF IN(+)
REF IN(–)
AV
DD
AD7715
0.1
m
F
ANALOG
GROUND
DIFFERENTIAL
ANALOG INPUT
DIGITAL
GROUND
0.1
m
F
10
m
F
V
OUT
V
IN
GND
AD780
ANALOG
+5V SUPPLY
DATA READY
RECEIVE (READ)
SERIAL DATA
SERIAL CLOCK
CRYSTAL OR
CERAMIC
RESONATOR
+5V
0.1
m
F
10
m
F
ANALOG
+5V SUPPLY
RESET
CS
DRDY
Figure 2. AD7715-5 Basic Connection Diagram
ANALOG INPUT
Analog Input Ranges
The AD7715 contains a differential analog input pair AIN(+)
and AIN(–). This input pair provides a programmable-gain,
differential input channel which can handle either unipolar or
bipolar input signals. It should be noted that the bipolar input
signals are referenced to the respective AIN(–) input of the
input pair.
In unbuffered mode, the common-mode range of the input is
from AGND to AV
DD
provided that the absolute value of the
analog input voltage lies between AGND–30mV and
AV
DD
+30mV. This means that in unbuffered mode the part
can handle both unipolar and bipolar input ranges for all gains.
In buffered mode, the analog inputs can handle much larger
source impedances but the absolute input voltage range is re-
stricted to between AGND+ 50mV to AV
DD
– 1.5V which
also places restrictions on the common-mode range. This means
that in buffered mode there are some restrictions on the allow-
able gains for bipolar input ranges. Care must be taken in set-
ting up the common-mode voltage and input voltage range so
that the above limits are not exceeded, otherwise there will be a
degradation in linearity performance.
In unbuffered mode, the analog inputs look directly into the
input sampling capacitor, C
SAMP
. The dc input leakage current
in this unbuffered mode is 1nA maximum. As a result, the
analog inputs see a dynamic load that is switched at the input
sample rate (see Figure 3). This sample rate depends on master
clock frequency and selected gain. C
SAMP
is charged to AIN(+)
and discharged to AIN(–) every input sample cycle. The effec-
tive on-resistance of the switch, R
SW
, is typically 7k
.
HIGH
IMPEDANCE
1G
V
R
SW
(7k
V
TYP)
C
(10pF )
V
BIAS
SWITCHING FREQUENCY
DEPENDS ON
f
CLKIN
AND SELECTED GAIN
AIN(+)
AIN(–)
Figure 3. Unbuffered Analog Input Structure
相關(guān)PDF資料
PDF描述
EVAL-AD7716EB Evaluation Board For 22-Bit Data Acquisition System
EVAL-AD7719EB Connector Backshell
EVAL-AD7730LEB 10K RESISTOR 1/10 W
EVAL-AD7730EB Bridge Transducer ADC
EVAL-AD7731EB Low Noise, High Throughput 24-Bit Sigma-Delta ADC
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
EVAL-AD7716EB 制造商:Analog Devices 功能描述:LC2MOS 22-BIT DATA ACQUISITION SYSTEM 制造商:Analog Devices 功能描述:EVALUATION BOARD - Bulk
EVAL-AD7716EBZ 制造商:Analog Devices 功能描述:EVAL BRD AD7716 - Bulk
EVAL-AD7718EB 制造商:Analog Devices 功能描述:Evaluation Kit For 8-/10-Channel, Low Voltage, Low Power, Segma-Delta ADCs 制造商:Rochester Electronics LLC 功能描述:EVALUATION BOARD I.C. - Bulk
EVAL-AD7718EBZ 功能描述:BOARD EVALUATION FOR AD7718 RoHS:是 類(lèi)別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 模數(shù)轉(zhuǎn)換器 (ADC) 系列:- 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- ADC 的數(shù)量:1 位數(shù):12 采樣率（每秒）:94.4k 數(shù)據(jù)接口:USB 輸入范圍:±VREF/2 在以下條件下的電源（標(biāo)準(zhǔn)）:- 工作溫度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，軟件
EVAL-AD7719EB 制造商:Analog Devices 功能描述:Evaluation Board For Low Voltage, Low Power, Factory-Calibrated 16-/24-Bit Dual-ADC 制造商:Analog Devices 功能描述:EVALUATION BOARD I.C. - Bulk
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*