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ACS752 Current Sensor ICs Frequently Asked Questions 
- What are the differences between the –100 and –050 versions of the ACS752?
- Can the ACS752 family be applied to both DC and AC currents?
- Can the ACS752 be applied to 0 to 200 A as well as ±100 A?
- What does "ratiometric" mean?
- What external components are required?
- Is there any way to adjust the gain of the ACS752?
- How small of a current can the ACS752 resolve?
- Can Allegro bend the leads under the package or outward, so that I can surface-mount the ACS752?
- How should I solder the ACS752 onto my board?
- Do you have a recommended footprint for the ACS752 (CA package)?
- Can I get the Gerber files for your evaluation board?
- I can't use Gerber files; is any other format available?
- Are there any other design guidelines for applying the ACS752?
- What is the inductance of the ACS752 (CA package)?
- What is the overcurrent handling capability of the ACS752?
- Does the ACS752 contain lead?
- What is the high-current leadframe made of?
- How susceptible is the ACS752 to stray magnetic fields?
- What safety certifications does the ACS752 have?
- What is the behavior of the ACS752 output during a slow ramp-up of VCC?
- How soon after the application of power will a valid signal be available from the ACS752?
- How will capacitive coupling between the current path in the ACS752 and the Hall plate effect the sensor IC output?
- What happens if I try to drive more than the specified 10 nF maximum capacitance with the output of the sensor IC?
- What happens if I try to drive less than the specified 4.7 kΩ minimum resistance with the output of the sensor IC?
- What is the ESD tolerance of the ACS752?
What are the differences between the –100 and –050 versions of the ACS752?
The only difference between the two versions of the device is the sensitivity. For the -050 version, sensitivity is set to 40 mV per ampere, while the -100 version is set to 20 mV per ampere.
Can the ACS752 family be applied to both DC and AC currents?
The ACS752 family uses Hall effect technology, which is affected by electrical currents having both DC and AC components. As the datasheet states, the bandwidth of the ACS752 is 50 kHz typical. There is usually a phase lag of at least 45º on the output for ac currents at frequencies exceeding 50 kHz. For transient current signals, the response time can be expected to be ~8 µs.
Can the ACS752 be applied to 0 to 200 A as well as ±100 A?
No, the maximum current for the ACS752 is an absolute current of 100 A. The magnetic circuit within the ACS752 package will not provide a linear output above field levels generated by 100 A.
This feature is particularly valuable when using the ACS752 with an analog-to-digital converter. A/D converters typically derive their LSB from a reference voltage input. If the reference voltage varies, the LSB will vary proportionally. The ratiometric feature of the ACS752 means its gain and offsets are proportional to its supply voltage, VCC. If the reference voltage and the supply voltage for the ACS752 are derived from the same source, the ACS752 and the A/D converter will both track those variations, and such variations will not be a source of error in the analog-to-digital conversion of the ACS752’s output.
What external components are required?
Allegro recommends the use of a 0.1 µF bypass capacitor between the Vcc pin and the GND pin. The capacitor should be located as close as practical to the ACS752 package body.
Is there any way to adjust the gain of the ACS752?
No, the ACS752 sensitivity and 0-ampere quiescent voltage level are programmed at the factory.
How small of a current can the ACS752 resolve?
Without filtering, the ACS752 50 A version can resolve a change in current level of ~3.6% of full scale, at 25ºC, through its primary conductor leads. The 100A version can resolve ~2.7%. At these levels, the amount of magnetic field coupled into the linear Hall Effect IC is just above its noise floor. However, depending on the temperature, 0-ampere offset error, and the dc current level, the percentage error of the current sensor IC output will often be greater than this minimum resolvable current.
The resolution can be increased by filtering the ACS752 output. A 50 kHz filter on the output improves the resolvable current resolution in the 50 A device to ~1.5% of full scale, and to ~1% of full scale for the 100 A version. Resolution can be further enhanced by lowering the filter value below 50 kHz, although the effective bandwidth of the sensor IC is reduced by filter values less than 50 kHz.
The following oscilloscope plots present performance characteristics:
ACS752-050 output with no filtering, ac coupled  |
ACS752-050 output with 50 kHz filter (R= 320 Ohm,
C=0.01 µF), ac coupled  |
ACS752-100 output with no filtering, ac coupled  |
ACS752-100 output with 50 kHz filter (R= 320 Ohms,
C=0.01 µF), ac coupled  |
Can Allegro bend the leads under the package or outward, so that
I can surface-mount the ACS752?
In order to safely conduct 100 A currents, the power leadframe in the ACS752 has been constructed with a relatively heavy gauge. Because of this heavy gauge, the terminal leads are not very flexible. If the ACS752 is surface-mounted, small amounts of board flex, or the action over time of thermal expansion and contraction, would break the IC off the board. Allegro does not believe surface-mounting is practical for this device.
How should I solder the ACS752 onto my board?
To ensure a robust joint to the board, Allegro recommends adding a ring of through-holes in the solder pad area around each of the two broad terminals that carry the current being sampled. These holes are shown in the diagram in the FAQ "Do you have a recommended footprint for the ACS752 (CA package)?". General soldering recommendations for the CA package, which is used for the ACS752, have been added to the application note Soldering Methods for Allegro Products (SMD and Through-Hole), which is on the Allegro website at www.allegromicro.com/en/Products/Design/an/an26009.pdf. The application note Guidelines for Designing Subassemblies Using Hall-Effect Devices contains signal lead welding recommendations and temperature guidelines.
Do you have a recommended footprint for the ACS752 (CA package)?
Yes, the following shows the recommended footprint.
Can I get the Gerber files for your evaluation board?
Yes, contact your Allegro sales representative.
I can't use Gerber files; is any other format available?
Yes, an AutoCAD 2004 .DXF file can be downloaded from: http://www.allegromicro.com/en/Products/Part_Numbers/0752/Allegro_CA_CB_EvalBoardDXF.zip.
The copper areas are defined as "regions" in these files.
Are there any other design guidelines for applying the ACS752?
Care should be taken to minimize the inductance of the current path to be measured. Also, attention should be paid to minimizing the contact/connection resistance of any connections in that path.
What is the inductance of the ACS752 (CA package)?
Typical measured inductance versus test signal frequency are:
- 40 nH at 10 kHz
- 35 nH at 100 kHz
- 33 nH at 200 kHz
What is the overcurrent handling capability of the ACS752?
Bench testing indicates the following typical, 1-second overcurrent tolerances for the CA package at a 1% duty cycle (1 second duration, repeated every 100 seconds)
- 25°C at 800 A
- 85°C at 600 A
- 150°C at 425 A
No, the ACS752 family is lead-free. All leads are coated with 100% matte tin, and there is no lead inside the package.
What is the high-current leadframe made of?
The heavy gauge leadframe is made of oxygen-free copper.
How susceptible is the ACS752 to stray magnetic fields?
The ACS752 contains a ferrite core that acts not only as a concentrator of the flux lines generated by Iprimary, but also as a shield to protect the sensor IC from ambient common-mode fields (typical rejection of common mode fields is -32 dB). The results are detailed in the following chart, which compares the output voltages, Vout, of an unshielded linear Hall effect sensor IC with that of the ACS752. The devices have the same gain, and are exposed to the same magnetic field, applied in an air core through the top of the package.
What safety certifications does the ACS752 have?
The ACS752 is UL94V-0 compliant. The ACS752 family also has been certified by TÜV America to the following standards:
- UL 60950-1:2003
- EN 60950-1:2001
- CAN/CSA C22.2 No. 60950-1:2003
What is the behavior of the ACS752 output during a slow ramp-up of Vcc?
The typical output behavior of the ACS752xCA-050 during a 500 ms ramp-up of Vcc is shown for both 0 A and 50 A in the following two charts:
How soon after the application of power will a valid signal be available from the ACS752?
The typical time to valid output is given in the following table and charts.
IP = 0 A |
IP = 50 A |
15 μs |
20 μs |
Startup of ACS752 with 0 amperes applied, then a VCC step from 0 to 5 V
Startup of ACS752 with 50 amperes applied, then a VCC step from 0 to 5 V
How will capacitive coupling between the current path in the ACS752 and the Hall plate effect the sensor IC output?
The typical capacitive coupling of a 20 V peak-to-peak signal on the current path is given in the following table.
| Noise Frequency |
Passed-Through Signal Magnitude |
Attenuation |
|---|---|---|
10 MHz |
270 mV/20 V |
–37.4 dB |
5 MHz |
65 mV/20 V |
–49.8 dB |
1 MHz |
30 mv/20 V |
–56.4 dB |
What happens if I try to drive more than the specified 10 nF maximum capacitance with the output of the sensor IC?
The output of the sensor IC may oscillate.
What happens if I try to drive less than the specified 4.7 kΩ minimum resistance with the output of the sensor IC?
The sensor IC may not produce an output, as its output driver will not be able to supply sufficient current.
What is the ESD tolerance of the ACS752?
Typical ESD tolerance is 6 kV human body model, 600 V machine model.