欢迎访问ic37.com |
会员登录 免费注册
发布采购

CS5460A-BS 参数 Datasheet PDF下载

CS5460A-BS图片预览
型号: CS5460A-BS
PDF下载: 下载PDF文件 查看货源
内容描述: 单相双向功率/电能IC [Single Phase Bi-Directional Power/Energy IC]
分类和应用:
文件页数/大小: 54 页 / 879 K
品牌: CIRRUS [ CIRRUS LOGIC ]
 浏览型号CS5460A-BS的Datasheet PDF文件第29页浏览型号CS5460A-BS的Datasheet PDF文件第30页浏览型号CS5460A-BS的Datasheet PDF文件第31页浏览型号CS5460A-BS的Datasheet PDF文件第32页浏览型号CS5460A-BS的Datasheet PDF文件第34页浏览型号CS5460A-BS的Datasheet PDF文件第35页浏览型号CS5460A-BS的Datasheet PDF文件第36页浏览型号CS5460A-BS的Datasheet PDF文件第37页  
CS5460A  
The  
voltage/current-channel  
inputs  
have  
to avoid using values for the protection resistors  
that are excessively high. A typical value for RV+  
would be 470 .  
surge-current limits of 100 mA. This applies to brief  
voltage/current spikes (<250 ms). The limit is  
10 mA for DC input overload situations. To prevent  
permanent damage to the CS5460A, the designer  
must include adequate protection circuitry in the  
power meter design, to insure that these pin cur-  
rent limits are never exceeded, when CS5460A is  
operating in the intended power-line metering envi-  
ronment.  
The VIN- pin should also have a protection resistor  
(called RV- in Figure 7). To maintain symmetry, the  
value of RV- should be made equal to RV+.  
For the current channel inputs (Iin+ and Iin-), if the  
maximum current rating (Imax) for this power line is  
30 A (RMS), then a suitable turns ratio for the cur-  
rent-sense transformer might be 200:1. Since the  
maximum load for a 120 VAC line rated at 30 A  
would be 4 (for unity power factor), a brief 8 kV  
surge across “L” and “N” could generate as much  
as 2000 A (RMS) of current through the primaries  
of the current-sense transformer. This can in turn  
generate as much as 10 V across the secondaries  
of the current-sense transformer. This voltage is  
high enough to turn on one or more of the internal  
protection diodes located off of the Iin+/Iin- pins.  
Therefore, the value of the protection resistor that  
will limit the current flow to less than 100 mA would  
be (10 V - 7 V) / 100 mA = 30 . In order to pro-  
vide some margin and to use the same resistor val-  
ues that are used on the Vin+/Vin- pins, a 470 Ω  
resistor can be used as a lower limit for the RI+ and  
RI- resistors shown in Figure 7.  
Focusing specifically on Figure 7, which shows  
how voltage/current transformers can be used to  
sense the line-voltage/line-current, suppose for ex-  
ample that the requirements for a certain 120 VAC  
power system require that the power meter must  
be able to withstand up to a 8 kV voltage spike on  
the power line during normal operating conditions.  
To provide a suitable sensor voltage input level to  
the voltage channel input pins of the CS5460A, the  
turns ratio of the voltage-sense transformer should  
be chosen such that the ratio is, for example, on  
the order of 1000:1. A voltage-sense transformer  
with a 1000:1 turns ratio will provide a 120 mV  
(rms) signal to the CS5460A’s differential voltage  
channel inputs, when the power line voltage is at  
the nominal level of 120 VAC. Therefore, a brief  
8 kV surge would be reduced to a 8 V surge across  
RV+.  
Referring to the circuit implementations shown in  
Figures 6, 8, and 9, note that when resistor-divider  
configurations are used to provide the voltage  
channel sense voltage, the VIN+ pin does not need  
an additional, separate, dedicated protection resis-  
tor. This is because the resistive voltage-divider al-  
ready provides the series resistance that is needed  
for this protection resistance (from R1 and R2).  
(And note in Figure 8 that this is true for both the  
VIN+ pin and the VIN- pin.) In Figure 7, a voltage  
transformer is used as the voltage sensor. When  
any type of transformer is used as the sensor de-  
vice for voltage (or current) channel, a dedicated  
protection resistor RV+ should be installed in series  
with the VIN+ pin, and similarly, a resistor (RV-)  
should be installed in series to the VIN- input pin.  
What happens when 8 volts (common-mode) is  
present across one of the analog input pins of the  
CS5460A? The Vin+/Vin- and Iin+/Iin- pins of the  
CS5460A are equipped with internal protection di-  
odes. If a voltage is presented to any of these pins  
that is larger than approximately 7 V (with respect  
to VA- pin) these protection diodes will turn on in-  
side the CS5460A. But in order to prevent exces-  
sive current levels from flowing through the device,  
the value of RV+ must be large enough that when a  
8V surge is present across the secondaries of the  
voltage-sense transformer, the brief surge current  
through RV+ should not be any greater than  
100 mA. Therefore, a minimum value for RV+  
would be (8 V - 7 V) / 100 mA = 10 . This value  
may be increased as needed, to easily obtain the  
desired cutoff frequency of the anti-aliasing filter on  
the voltage channel (described later), and also to  
provide some margin. But the designer should try  
Additional considerations/techniques regarding  
the protection of the analog input pins against sud-  
den high-frequency, high-level voltage/current  
surges are discussed in Section 3.14.  
33