參數(shù)資料
型號(hào)： LTC1966HMS8#PBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 模擬專用變換器
英文描述： RMS TO DC CONVERTER, PDSO8
封裝： LEAD FREE, PLASTIC, MSOP-8
文件頁(yè)數(shù)： 21/38頁(yè)
文件大小： 387K
代理商： LTC1966HMS8#PBF
LTC1966
28
1966fb
applicaTions inForMaTion
Interfacing with an ADC
The LTC1966 output impedance and the RMS averaging
ripple need to be considered when using an analog-to-
digitalconverter(ADC)todigitizetheLTC1966RMSresult.
The simplest configuration is to connect the LTC1966
directly to the input of a type 7106/7136 ADC as shown
in Figure 25a. These devices are designed specifically for
DVM/DPM use and include display drivers for a 3 1/2 digit
LCD segmented display. Using a dual slope conversion,
the input is sampled over a long integration window, which
resultsinrejectionoflinefrequencyripplewhenintegration
time is an integer number of line cycles. Finally, these parts
have an input impedance in the GΩ range, with specified
input leakage of 10pA to 20pA. Such a leakage, combined
with the LTC1966 output impedance, results in just 1V
to 2V of additional output offset voltage.
for are the input impedance, and any input sampling cur-
rents. The input sampling currents drawn by ∑ ADCs
often have large spikes of current with short durations
that can confuse some op amps, but with the large CAVE
needed by the LTC1966 these are not an issue.
The average current is important, as it can create LTC1966
errors; if it is constant it will create an offset, while aver-
age currents that change with the voltage level create gain
errors. Some converters run continuously, others only
sample upon demand, and this will change the results in
ways that need to be understood. The LTC1966 output
impedance has a loose tolerance relative to the usual re-
sistors and the same can be true for the input impedance
of ∑ ADC, resulting in gain errors from part-to-part. The
system calibration techniques described in the following
section should be used in applications that demand tight
tolerances.
One example of driving an oversampling ∑ ADC is shown
in Figure 25b. In this circuit, the LTC2420 is used with a
1V VREF. Since the LTC1966 output voltage range is about
1V, and the LTC2420 has a ±12.5% extended input range,
this configuration matches the two ranges with room to
spare. The LTC2420 has an input impedance of 16.6MΩ,
resulting in a gain error of –0.4% to –0.6%. In fact, the
LTC2420 DC input current is not zero at 0V, but rather at
one half its reference, so both an output offset and a gain
error will result. These errors will vary from part to part,
but with a specific LTC1966 and LTC2420 combination,
the errors will be fixed, varying less than ±0.05% over
temperature. So a system that has digital calibration can
be quite accurate despite the nominal gain and offset error.
With 20 bits of resolution, this part is more accurate than
the LTC1966, but the extra resolution is helpful because
it reduces nonlinearity at the LSB transitions as a digital
gain correction is made. Furthermore, its small size and
ease of use make it attractive.
Figure 25a. Interfacing to DVM/DPM ADC
Figure 25b. Interfacing to LTC2420
Another type of ADC that has inherent rejection of RMS
averagingrippleisanoversampling∑.Withmost,butnot
all, of these devices, it is possible to connect the LTC1966
output directly to the converter input. Issues to look out
CAVE
LTC1966
OUTPUT
OUT RTN
7106 TYPE
IN HI
IN LO
5
6
31
1966 F25a
30
CAVE
LTC1966
OUTPUT
OUT RTN
LTC2420
VIN
SERIAL
DATA
DIGITALLY CORRECT
LOADING ERRORS
GND
SDO
SCK
CS
5
6
3
1966 F25b
4
VREF
2
1V
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1966IMS8 功能描述:IC PREC RMS/DC CONV MCRPWR 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - RMS 至 DC 轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:46 系列:- 電流 - 電源:1.2mA 電源電壓:±18 V，36 V 安裝類型:表面貼裝 封裝/外殼:16-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC W 包裝:管件
LTC1966IMS8#PBF 功能描述:IC PREC RMS/DC CONV MCRPWR 8MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - RMS 至 DC 轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:46 系列:- 電流 - 電源:1.2mA 電源電壓:±18 V，36 V 安裝類型:表面貼裝 封裝/外殼:16-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC W 包裝:管件
LTC1966IMS8#TR 功能描述:IC PREC RMS/DC CONV MCRPWR 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - RMS 至 DC 轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:46 系列:- 電流 - 電源:1.2mA 電源電壓:±18 V，36 V 安裝類型:表面貼裝 封裝/外殼:16-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC W 包裝:管件
LTC1966IMS8#TRPBF 功能描述:IC PREC RMS/DC CONV MCRPWR 8MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - RMS 至 DC 轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:46 系列:- 電流 - 電源:1.2mA 電源電壓:±18 V，36 V 安裝類型:表面貼裝 封裝/外殼:16-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC W 包裝:管件
LTC1966IMS8PBF 制造商:Linear Technology 功能描述:RMS-to-DC Converter Prec. uPower MSOP8
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