參數(shù)資料
型號(hào)： LTC1966MPMS8#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)： 3/38頁(yè)
文件大小： 387K
代理商： LTC1966MPMS8#PBF
LTC1966
11
1966fb
applicaTions inForMaTion
How an RMS-to-DC Converter Works
Monolithic RMS-to-DC converters use an implicit com-
putation to calculate the RMS value of an input signal.
The fundamental building block is an analog multiply/
divide used as shown in Figure 3. Analysis of this topol-
ogy is easy and starts by identifying the inputs and the
output of the lowpass filter. The input to the LPF is the
calculation from the multiplier/divider; (VIN)2/VOUT. The
lowpass filter will take the average of this to create the
output, mathematically:
V
so
V
and
VV
or
VV
RMS V
OUT
IN
OUT
IN
OUT
IN
OUT
IN
OUT
IN
= ()
()
=
()
=
()
() = ()
=
() =
()
2
22
2
,
Because V
is DC,
V
OUT
IN
How the LTC1966 RMS-to-DC Converter Works
The LTC1966 uses a completely new topology for RMS-
to-DC conversion, in which a
S modulator acts as the
divider,andasimplepolarityswitchisusedasthemultiplier
as shown in Figure 4.
Figure 3. RMS-to-DC Converter with Implicit Computation
Unlike the prior generation RMS-to-DC converters, the
LTC1966 computation does NOT use log/antilog circuits,
whichhaveallthesameproblems,andmore,oflog/antilog
multipliers/dividers, i.e., linearity is poor, the bandwidth
changes with the signal amplitude and the gain drifts with
temperature.
Figure 4. Topology of LTC1966
The
S modulator has a single-bit output whose average
duty cycle (D) will be proportional to the ratio of the input
signal divided by the output. The
Sisa2ndordermodula-
tor with excellent linearity. The single bit output is used to
selectively buffer or invert the input signal. Again, this is a
circuit with excellent linearity, because it operates at only
two points: ±1 gain; the average effective multiplication
over time will be on the straight line between these two
points.Thecombinationofthesetwoelementsagaincreates
a lowpass filter input signal proportional to (VIN)2/VOUT,
which, as shown above, results in RMS-to-DC conversion.
The lowpass filter performs the averaging of the RMS
function and must be a lower corner frequency than the
lowest frequency of interest. For line frequency measure-
ments, this filter is simply too large to implement on-chip,
but the LTC1966 needs only one capacitor on the output
to implement the lowpass filter. The user can select this
capacitor depending on frequency range and settling time
requirements, as will be covered in the Design Cookbook
section to follow.
This topology is inherently more stable and linear than
log/antilog implementations primarily because all of the
signalprocessingoccursincircuitswithhighgainopamps
operating closed loop.
VIN
VOUT
1966 F03
× ÷
LPF
V
IN
OUT
()2
–∑
REF
VIN
VOUT
LPF
±1
D
V
IN
OUT
α
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參數(shù)描述
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LTC1967CMS8#PBF 功能描述:IC CONVERTER RMS-DC PREC 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
LTC1967CMS8#TR 功能描述:IC CONVERTER RMS-DC PREC 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
LTC1967CMS8#TRPBF 功能描述:IC CONVERTER RMS-DC PREC 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
LTC1967CMS8PBF 制造商:Linear Technology 功能描述:RMS-DC converter, LTC1967 40kHz MSOP
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