ALLEGRO micro Systems CT428-20AC Xtreme Sense Isolated Current Sensor
DESCRIPTION
The Allegro Micro Systems CTD428-20AC evaluation board contains the CT428—Xtreme Sense™ tunnel magnetoresistance (TMR) integrated circuit (IC). This user guide describes the operation and use of the evaluation board as an engineering tool for evaluating the CT428 IC performance in application.
FEATURES
- Integrated current-carrying conductor
- Linear analog output voltage
- Response time: ~300 ns
- Low noise
- Filter function to reduce noise on output pin
- Immunity to common mode fields: –54 dB
- Overcurrent detection
- Supply voltage: 3 V to 3.6 V
EVALUATION BOARD CONTENTS
- CT428-20AC evaluation board
Table 1: CT428-20AC Evaluation Board Configurations
| Configuration Name | Part Number | Sensitivity | Bandwidth |
| CT428-20AC Evaluation Board | CTD428-HSN820MR | 20 mV/V | 1 MHz |
Table 2: General Specifications
| Specification | Min | Nom | Max | Units |
| Input Operating Temperature | –40 | – | 125 | ºC |
| Input Operating Current | –20 | – | 20 | A |
USING THE EVALUATION BOARD
Introduction
The CT428 is a high-bandwidth and ultra-low-noise integrated contact current sensor that uses Allegro-patented Xtreme Sense™ TMR technology to enable high-accuracy current measurements for many consumer, enterprise, and industrial applications. The device supports eight current ranges where the integrated current-carrying conductor (CCC) handles up to 65 A of current and generates a current measurement as a linear analog output voltage. The device achieves a total output error of less than ±1% full-scale (FS).The device has a 300 ns output response time when the current consumption is ~6 mA, and it is immune to common-mode fields. The CT428 has an integrated overcurrent detection (OCD) circuit to identify out-of-range currents (OCD), and the result is output to the fault-bar (FLT) pin.
The FLT is an open-drain, active-low digital signal that is activated by the CT428 to alert the microcontroller that a fault condition has occurred. The CT428 is offered in an industry-standard 8-lead small-outline integrated circuit (SOIC) package that is green and Restriction of Hazardous Substances (RoHS) compliant.
This section provides an overview of the connections and configuration options of the CT428 evaluation board. The proper configuration is highlighted and detailed in Figure 2. The CT428 datasheet contains detailed information about the use and functionality of each pin and detailed specifications about the sensor. For more detailed information, refer to the product datasheet.
Power Input
The two large connectors (with screws) are used to connect and drive the external current to be measured. Due to the PCB trace thermal limitation of the CT428 evaluation board, do not exceed 20 APK.
Board Configuration
A fully assembled evaluation board is illustrated in Figure 1 and Figure 2. The current to be measured is connected to the screw connectors located on the right side of the PCB. These connectors are galvanically isolated from the rest of the PCB. The CT428 can be biased by applying a 3.3 V bias voltage between the VDD and GND pins on the PCB and its output can be measured either from the VOUT SMA connector or the VOUT header pin on the PCB.
SCHEMATIC
The schematic of the CT428-20AC evaluation board is shown in Figure 3.
LAYOUT
The top and bottom layers of the CT428-20AC evaluation board are shown in Figure 4 and Figure 5, respectively.
BILL OF MATERIALS
| Designator | Quantity | Description | Manufacturer | Manufacturer Part Number |
| PCB | 1 | CT428-20AC evaluation board | Allegro Micro Systems | – |
| U1 | 1 | CT428 sensor | Allegro Micro Systems | – |
| C1 | 1 | 1.0 µF, X5R or better SMD Capacitor 0603 | TDK | CGA3E1X7R1E105K080AC |
| R2 | 1 | 10 kΩ, ±10% or better SMD Resistor 0603 | Panasonic, AVX, Yageo | ERJ-3GEYJ103V |
| R1 | 1 | 100 kΩ, ±10% or better SMD Resistor 0603 | Yageo | RC0603FR-07100KL |
| Vout | 1 | SMA Connector | Clinch Connectivity | 142-0701-201 |
| J1, J2 | 2 | Screw Connectors | Keystone, Blockmaster | 534-7701 |
| J2 | 1 | M3 Terminal Screw Red | Keystone | 36-7701-2 |
| J1 | 1 | M3 Terminal Screw Black | Keystone | 36-7701-3 |
| GND, FLTB_ VDD, FLTB, VDD, P2 | 5 | Male Header Connectors – Single pin | Wurth Elektronik | 732-5334-ND |
CT428 product page:
For samples or applications support contact, visit https://www.allegromicro.com/en/about-allegro/contact-us/technical-assistance and navigate to the appropriate region.
Revision History
| Number | Date | Description |
| – | August 7, 2024 | Initial release |
CUSTOMER SUPPORT
Copyright 2024, Allegro Micro Systems.
Allegro Micro Systems reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current.
Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro Micro Systems assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use.
Copies of this document are considered uncontrolled documents.
Allegro Micro Systems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Documents / Resources
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ALLEGRO micro Systems CT428-20AC Xtreme Sense Isolated Current Sensor [pdf] User Guide CT428-20AC, CTD428-HSN820MR, CT428-20AC Xtreme Sense Isolated Current Sensor, CT428-20AC, Xtreme Sense Isolated Current Sensor, Isolated Current Sensor, Current Sensor, Sensor |
