- 您现在的位置：买卖IC网 > PDF目录22190 > LTC1968CMS8#PBF (Linear Technology)IC CONVERTER RMS-DC PREC 8MSOP PDF资料下载
参数资料
| 型号： | LTC1968CMS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 20/28页 |
| 文件大小： | 296K |
| 描述： | IC CONVERTER RMS-DC PREC 8MSOP |
| 标准包装： | 50 |
| 电流 - 电源： | 2.3mA |
| 电源电压： | 5.0V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 8-MSOP |
| 包装： | 管件 |
| 产品目录页面： | 1338 (CN2011-ZH PDF) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页当前第20页第21页第22页第23页第24页第25页第26页第27页第28页
20
LTC1968
1968f
V
OUT
= ((5mV AC)
2
+ (0.4mV DC)
2
) " 1.001 + 0.2mV
= 5.221mV
= 5mV + 4.42%
As can be seen, the gain term dominates with large inputs,
while the offset terms become significant with smaller
inputs. In fact, 5mV is the minimum RMS level needed to
keep the LTC1968 calculation core functioning normally,
so this represents the worst-case of usable input levels.
Using the worst-case values of the LTC1968 static errors,
the total conversion error is:
V
OUT
= ((500mV AC)
2
+ (1.5mV DC)
2
) " 1.003 + 0.75mV
= 502.25mV
= 500mV + 0.45%
V
OUT
= ((50mV AC)
2
+ (1.5mV DC)
2
) " 1.003 + 0.75mV
= 50.923mV
= 50mV + 1.85%
V
OUT
= ((5mV AC)
2
+ (1.5mV DC)
2
) " 1.003 + 0.75mV
= 5.986mV
= 5mV + 19.7%
These static error terms are in addition to dynamic error
terms that depend on the input signal. See the Design
Cookbook for a discussion of the DC conversion error with
low frequency AC inputs. The LTC1968 bandwidth limita-
tions cause additional errors with high frequency inputs.
Another dynamic error is due to crest factor. The LTC1968
performance versus crest factor is shown in the Typical
Performance Characteristics.
Output Errors Versus Frequency
As mentioned in the design cookbook, the LTC1968 per-
forms very well with low frequency and very low frequency
inputs, provided a large enough averaging capacitor is used.
However, the LTC1968 will have additional dynamic errors
as the input frequency is increased. The LTC1968 is de-
signed for high accuracy RMS-to-DC conversion of sig-
nals up to 100kHz. However, the switched capacitor cir-
cuitry samples the inputs at a modest 2MHz nominal. The
response versus frequency is depicted in the Typical Per-
formance Characteristics titled Input Signal Bandwidth.
APPLICATIO S I FOR ATIO
U
U
U
Although there is a pattern to the response versus fre-
quency that repeats every sample frequency, the errors
are not overwhelming. This is because LTC1968 RMS
calculation is inherently wideband, operating properly with
minimal oversampling, or even undersampling, using sev-
eral proprietary techniques to exploit the fact that the RMS
value of an aliased signal is the same as the RMS value of
the original signal. However, a fundamental feature of the
?modulator is that sample estimation noise is shaped
such that minimal noise occurs with input frequencies
much less than the sampling frequency, but such noise
peaks when input frequency reaches half the sampling
frequency. Fortunately the LTC1968 output averaging fil-
ter greatly reduces this error, but the RMS-to-DC topology
frequency shifts the noise to low (baseband) frequencies.
See Output Noise vs Input Frequency in the Typical Perfor-
mance Characteristics.
Input Impedance
The LTC1968 true RMS-to-DC converter utilizes a 0.8pF
capacitor to sample the input at a nominal 2MHz sample
frequency. This accounts for the 1.2M& input impedance.
See Figure 20 for the equivalent analog input circuit. Note
however, that the 1.2M& input impedance does not di-
rectly affect the input sampling accuracy. For instance, if
a 15.5k source resistance is used to drive the LTC1968, the
sampling action of the input stage will drag down the
voltage seen at the input pins with small spikes at every
sample clock edge as the sample capacitor is connected to
be charged. The time constant of this combination is
small, 0.8pF " 15.5k& = 12.5ns, and during the 125ns
period devoted to sampling, ten time constants elapse.
Figure 20. LTC1968 Equivalent Analog Input Circuit
IN1
V
DD
V
DD
V
SS
V
SS
R
SW
(TYP)
2k
C
EQ
0.8pF
(TYP)
C
EQ
0.8pF
(TYP)
I
IN1
IN2
I
IN2
1968 F20
R
SW
(TYP)
2k
IIN
V V
R
IIN
V V
R
R
M
AVG
IN IN
EQ
AVG
IN IN
EQ
EQ
1
2
1.2
1 2
2 1
( )
=
( )
=
=
&
相关PDF资料 |
PDF描述 |
|---|---|
| RAC20-05DA | CONV AC/DC 2A 6.5-18VIN 3.0-5.5V |
| 1N5398S-T | DIODE STD REC 1.5A 800V DO-41 |
| NCP612SQ28T2G | IC REG LDO 2.8V .2A SC70-5 |
| GCM06DSEI-S243 | CONN EDGECARD 12POS .156 EYELET |
| V150B48C250BL2 | CONVERTER MOD DC/DC 48V 250W |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1968IMS8 | 功能描述:IC CONVERTER RMS-DC PREC 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| LTC1968IMS8#PBF | 功能描述:IC CONVERTER RMS-DC PREC 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| LTC1968IMS8#TR | 功能描述:IC CONVERTER RMS-DC PREC 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| LTC1968IMS8#TRPBF | 功能描述:IC CONVERTER RMS-DC PREC 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| LTC1980EGN | 功能描述:IC PWM BATT CHARGER/CONV 24-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 功能:电池监控器 电池化学:碱性，锂离子，镍镉，镍金属氢化物 电源电压:1 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-6 供应商设备封装:SOT-6 包装:带卷 (TR) |
发布紧急采购，3分钟左右您将得到回复。