FAQ - AK31 系列

AK31 Series

[Q0464]
・Are there any precautions when using this product for the first time?
A.
・The Zero-Current Output of the AK310x may drift over time within the values defined in datasheet Section 14.
Therefore, in order to minimize this drift, we recommend calibrating the Zero-Current Output by software after the power-up time of the system when the measured current is zero.
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[Q0475]
・Is it possible to sense both DC current and AC current?
A.
・It is possible to sense both DC current and AC current.
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[Q0476]
・What is the difference between maximum primary current and linear sensing range?
A.
・Maximum primary current indicates the current value which can be applied for a long time in a current sensor and depends on the cross-sectional area of the primary conductor.
AK310x can be damaged when they have been used for a long time over the maximum effective current value. If current flows at a short period within msec order, such as an over current, AK310x is not damaged.
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[Q0477]
・How much current can be flown in AK310x?
A.
・It is possible to flow current of up to 20Arms in AK310x.
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[Q0478]
・Can AK310x detect unipolar current?
 (ex. Current detection of 0 to 21A)
A.
・AK310x can not detect unipolar current.
However, the customized products are possible depending on quantity conditions and requirement.
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[Q0479]
・How small current can the AK310x resolve?
A.
・The current resolution is determined by its output noise voltage.
The current resolution can be increased by applying a noise filtering circuit.
(a) 1μF bypass capacitor should be placed close to VDD and VSS pins of AK310x.
(b) Add a low-pass filter if it is necessary. 
The C1 values should be fixed in consideration of load conditions.
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[Q0480]
・How much is the temperature drift of the primary conductor resistance of AK310x?
A.
・The temperature drift of the primary conductor resistance of AK310x is shown in Figure 1.
Figure1. AK310x Tempetature Drift of the Primary Conductor Resistance (normalized at 25℃)
Figure1. AK310x Tempetature Drift of the Primary Conductor Resistance (normalized at 25℃)
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[Q0481]
・What is the variation in primary conductor resistance?
A.
・The primary conductor resistance of AK310x varies from 1.2 to 2.1mΩ (reference) at 25°C.
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[Q0482]
・What is the inductance of the primary conductor?
A.
・The Primary Conductor Inductance of AK310x is about 2.7nH (reference) at 25°C.
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[Q0483]
・What does "ratiometric" mean?
A.
・The AK310x has a ratiometric output. This means that the output of the current sensor changes proportionally to the supply power voltage. A ratiometric output is suitable for applications where the output is converted to digital using an A/D converter and where fluctuation of the power supply voltage causes reference error of the A/D converter.   
[Q0502] External Circuit Case 1) shows an example of the external circuit where a 5V A/D converter is connected. [Q0502] External Circuit Case 2) shows the case where a 3V A/D is used. The supply voltage of the AK310x and the reference voltage of A/D converter fluctuate at the same ratio. This will avoid the effects of the fluctuation of the power supply to the A/D converter output.
 Figure 2 shows the output voltage of the AK3103 (Sensitivity Vh=60mV/A) as an example ratiometric output.
Figure 2. Output voltage of the AK3103 vs Input Current with different VDD.
Figure 2. Output voltage of the AK3103 vs Input Current with different VDD.
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[Q0485]
・What is the frequency characteristics of AK310x?
A.
・The graph in Figure 3 shows the typical frequency characteristics of the AK310x.
The plot on the top shows the amplitude and the plot on the bottom shows the phase delay.
Figure 3. Frequency Response of the AK310x
Figure 3. Frequency Response of the AK310x
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[Q0486]
・What is the response time?
A.
・Response time is TYP 2.0μs.(In the case of load capacity of 100pF)
Figure 4 shows the rise response and fall response waveform of AK310x.
Figure 4. Rise response waveform (left), fall response waveform (right).
Figure 4. Rise response waveform (left), fall response waveform (right).
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[Q0487]
・What is the recovery time from a fully saturated output?
A.
・The AK310x VOUT response time from deep saturation was measured at less than 3.0 µs. Figure 5 shows the oscilloscope plot of AK3101 transient response waveform.
Figure 5.  The AK3101 Transient Response Waveform from the VOUT Deep Saturation. Test conditions:for saturation, IIN=15A; for linear VOUT, IIN=0A.
Figure 5. The AK3101 Transient Response Waveform from the VOUT Deep Saturation. Test conditions:for saturation, IIN=15A; for linear VOUT, IIN=0A.
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[Q0488]
・What happens if a load capacitance over 100pF is inserted to the AK310x VOUT?
A.
・AK310x does not output the correct value because of the oscillation of output.
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[Q0489]
・What happens if a load current over +/-0.5mA is applied to AK310x VOUT?
A.
・In this case the AK310x does not output the correct value.
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[Q0490]
・Does AK310x show magnetic hysteresis?
A.
・No, because AK310x does not contain magnetic material.
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[Q0491]
・What safety standards AK310x have?
A.
・AK310x have been certified with IEC/UL-60950 and UL1577 by the international certification association.
・IEC/UL 60950-1 – Information Technology Equipment – Edition 2. (File No.E359197)
・CSA C22.2 NO. 60950-1-07 – Information Technology Equipment – Edition 2. (File No. E359197)
・UL1577 -Optical Isolators-Edition 5.(File No. E499004)
・IEC/UL62368-1 -Audio/video, Information and Communication Technology Equipment- 2nd Ed,(File No.E359197) 
・CAN/CSA C22.2 No.62368-1-14 -Audio/video, Information and Communication Technology Equipment- 2nd Ed,(File No.E359197)
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[Q0492]
・What is the clearance distance and the creepage distance?
A.
・The clearance distance and the creepage distance are both over 5.0mm.
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[Q0493]
・What is the CTI of the package?
A.
・The Comparative Tracking Index (CTI) of the AK310x package resin is 600V. The Material Group is I.
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[Q0494]
・How much is the working voltage of AK310x?
A.
・AK310x can be used under the following conditions.
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[Q0495]
・Is it allowable to use this device over the rating isolation voltage of the data-sheet?
A.
・The device should be used within a recommended condition.
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[Q0496]
・What is the voltage noise rejection ratio?
A.
・The Voltage Noise Rejection Ratio of the Primary Conductor was calculated by measuring the output while a high frequency sine wave voltage was applied as the input noise to the primary conductor.
Table 3 shows the AK310x series having a strong voltage noise rejection ratio.
Figure 6. shows the frequency dependency of the voltage noise rejection ratio.
Table 3. Typical Capacitive Coupling of 20 Vp-p Signal on the Sensed Current Path
Table 3. Typical Capacitive Coupling of 20 Vp-p Signal on the Sensed Current Path
Figure 6. AK310x noise rejection versus noise frequency
Figure 6. AK310x noise rejection versus noise frequency
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[Q0497]
・What are the constant parameters of RC?
A.
・Please decide the parameters considering the requirement of output resolution and response time (Please refer to [Q0479]).
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[Q0498]
・How should I solder the AK310x to the board?
A.
・Please refer to "Soldering condition" described in Important notices page.
Click here for details
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[Q0499]
・Is there the recommended land pattern?
A.
・Yes. The recommended land pattern is shown in Figure 7
Figure 7. Recommended Land Pattern of AK310x
Figure 7. Recommended Land Pattern of AK310x
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[Q0500]
・Are there any other board layout guidelines of AK310x?
A.
・Please see the application notes (2. Board Design Guidelines) here.
Click here for details
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[Q0501]
・Is gerber file of the evaluation board provided?
A.
・Yes, please download from: Gerber Files.
Click here for details
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[Q0502]
・What is the recommended circuit diagram to use the AK310x?
A.
・In this subsection, we show three examples of the external circuit when using AK310x.
These are just examples and there are other possible circuits. Please evaluate your external circuit by yourself.

Case 1) Connecting a 5V A/D converter in the subsequent stage
(a) 1.0μF bypass capacitor should be placed close to VDD and VSS pins of AK310x.
(b) Add a low-pass filter to VOUT pins if it is necessary. The R1 and C1 values should be fixed in consideration of the time constant of the filter and load conditions.

Case 2) Connecting a 3V A/D converter in the subsequent stage
(a) 1.0μF bypass capacitor should be placed close to VDD and VSS pins of AK310x.
(b) Add a low-pass filter to VOUT pins if it is necessary. The R1, R2 and C1 values should be fixed in consideration of the time constant and the resistive divider ratio.

Case 3) Connecting an amplifier to change the reference voltage
(a) 1.0μF bypass capacitor should be placed close to VDD and VSS pins of AK310x. 
(b) R1 and R2 are resistors that decides the gain. The R0 value should be fixed in consideration of the load condition. The R1 and R2 values should be fixed in consideration of the gain.
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[Q0503]
・I'm worried about the heat generated when applying a large current.
A.
・The AK310x is capable of 20Arms continuous current, even larger current in case of transitional. When AK310x is used under conditions compliant with the safety standard, please ensure the case temperature (Tc) is kept lower than 130℃ from heating by the primary current. Please refer to the Figure 8. for the position to measure Tc. 
If the heat dissipation is not enough, using thermal vias may help. These can increase heat dissipation without increasing the trace area by thermally connecting the primary conductors to an inner or outer thermal layer directly.
Figure 8. Position to measure package case temperature
Figure 8. Position to measure package case temperature
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[Q0504]
・What is the ESD tolerance?
A.
・AK310x has the ESD tolerance which is more than 2000V by human body model (HBM) and more than 200V by machine model (MM).
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[Q0505]
・How much does AK310x have influenced from the other current line?
A.
・The influence from other current lines, as shown in Figure 9, depends on the applied current of the other current lines and the distance between the AK310x and the other current lines.
For example, if you want to reduce the error within 400mA caused by the other line where 20A current flows, 
you need to  separate the other current line to the distance of 6mm or more as a distance A, 5mm or more as a distance B. 
Distance B is not only defined as the line on the left of AK310x package but also the line on the right of AK310x package.
Please do not place magnetic materials near the AK310x to avoid their influences.
Figure 9. Influence from other Current Line of AK310x
Figure 9. Influence from other Current Line of AK310x
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[Q0506]
・Is there a way to estimate the temperature of AK310x?
A.
・It is possible to estimate the internal temperature measuring the diode characteristics of the IC. (Technical Resource: Estimated method of the CQ-3 series IC internal temperature)
Click here for details
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[Q0507]
・What is the effect on the device characteristics with respect to temperature change?
A.
・The graphs below show the change in characteristics when the ambient temperature is changed from 25 to -40 ° C and 125 ° C.
Figure 10 shows temperature drift of sensitivity, Figure 11 shows temperature drift of zero-current output, and Figure 12 shows total accuracy.
All graphs show “Average” and “Average ±3σ” of the actual result in a certain lot.
Figure 10. Temperature Drift of Sensitivity (left), Figure 12.  Temperature dependency of Total Accuracy (right)
Figure 10. Temperature Drift of Sensitivity (left), Figure 12. Temperature dependency of Total Accuracy (right)
Figure 11. Temperature Drift of Zero-current Output
Figure 11. Temperature Drift of Zero-current Output
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[Q0508]
・What is the impact on output when the voltage or the current applied to the primary?
A.
・Figure 13. shows the dV/dt noise of AK310x output voltage (VOUT), when 1kV is applied to the primary conductor at the rise time of 1μs.
The yellow line shows the input voltage waveform and the green line shows the output voltage waveform.
The convergence time is as short as 3μs. It is easy to avoid this noise by adjusting the capture timing.

Figure 14. shows the output voltage (VOUT) of AK310x, when a 10A pulse is applied to the primary conductor with a pulse width of 1μs.
The yellow line shows the input current waveform and the green line shows the output voltage waveform.
The convergence time is as short as 3μs. It is easy to avoid this noise by adjusting the capture timing.
Figure 13. dV/dt noise waveform
Figure 13. dV/dt noise waveform
Figure 14. dI/dt noise waveform
Figure 14. dI/dt noise waveform
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[Q0509]
・Are AK310x halogen-free/RoHS?
A.
・AK310x are halogen-free/RoHS.
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[Q0510]
・Are AK310x Pb-free?
A.
・AK310x are Pb-free.
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[Q0511]
・What is the primary conductor made from?
A.
・The primary conductor is made from copper.
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[Q0512]
・Is it possible to use the internal EEPROM?
A.
・Sorry, internal EEPROM is not available.
Products will be shipped after the adjustment of EEPROM at factory test.
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[Q0513]
・Is it possible to order the customized products?
A.
・It is possible to customize depending on quantity conditions and requirement.
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[Q0514]
・Are there any precautions when using current sensors within the vacinity of stray magnetic fields/parts?
A.
・The AK310x output can be affected by magnetic devices (mechanical relays, transformers, etc.) that are nearby.
In the case where magnetic devices must be placed close to the AK310x, please check the effect on sensitivity or other characteristics and make sure any effects are understood and mitigated as much as possible.
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