ALLEGRO ACSEVB-CB5-SMT CB Current Sensor Evaluation Board User Guide
- June 17, 2024
- ALLEGRO
Table of Contents
ALLEGRO ACSEVB-CB5-SMT CB Current Sensor Evaluation Board User Guide
ACSEVB-CB5-SMT
CB (SMT) Package Generic Evaluation Board User Guide
DESCRIPTION
Generic evaluation boards offer a method for quickly evaluating Allegro current sensors in a lab environment without needing a custom circuit board. This document describes the use of the CB Current Sensor Evaluation Board. This evaluation board (ACSEVB-CB5-SMT, TED-0004118) is intended for use with any CB package (five-pin custom Allegro current sensor package).
FEATURES
- Enhanced thermal performance:
- Six-layer PCB with 2 oz copper weight on all layers
- Nonconductive, filled via-in-pad used
- High-performance FR4 material with 180°C glass transition temperature
- Flexible instrument connection:
- Standard Keystone test points; SMA/SMB connector or two-pin header options are provided
- Sensor-integrated current-loop resistance can be measured directly on the evaluation board; voltage drop can be measured for approximating power loss in the package
EVALUATION BOARD CONTENTS
-
Bare printed circuit board without populated components
NOTE: It is up to the user to assemble the board with the desired current sensor. This board does not come populated with an Allegro current sensor. -
Recommended bill of materials (BOM) for all compatible current sensors are listed in the Bill of Materials section.
USING THE EVALUATION BOARD
Evaluation Board Components
- U1 is a CB package footprint (Pin 1 is on bottom left side, see the small white dot)
- U1 pins allow the option to connect:
- RPU: Pull-up resistor to VCC
- RPD: Pull-down resistor to GND
- C: Decoupling or load capacitor to GND
- All passive components are 0603 package size
- Keystone 5005 test points (e.g., Digikey# 36-5005-ND)
- Standard SMB/SMA connector (e.g., Digikey# 1868-1429- ND)
- Two-pin, 100 mil header connector option NOTE: Either SMB or header can be assembled
- Primary current cables mounting positions (positive current flow direction is left to right)
- Two-pin, 100 mil header connector for voltage-drop measurement across the integrated current loop of the current sensor
- RB1, RB2, RB3, and RB4: rubber bumper mounting positions (e.g., Digikey# SJ61A6-ND)
Evaluation Board Procedure
CONNECTING TO THE EVALUATION BOARD
The best way to connect measurement instruments to the evaluation board is to use SMB/SMA or Two-pin header connectors along with coaxial cables. This configuration is most resilient to external coupling and is the preferred measurement method, e.g., for high speed dI/dt transients.
Keystone test points are convenient for connection of any instrument; however, this method is recommended for DC setups only.
EVALUATION BOARD PERFORMANCE DATA
Thermal Rise vs. Primary Current
Self-heating due to the flow of current in the package IP conductor should be considered during the design of any current sensing system. The sensor, printed circuit board (PCB), and contacts to the PCB generate heat and act as a heat sink as current moves through the system.
The thermal response is highly dependent on PCB layout, copper thickness, cooling techniques, and profile of the injected current. The current profile includes peak current value, current “ontime,” and duty cycle.
Placing vias under the copper pads of the Allegro current sensor evaluation board minimizes the current path resistance and improves heat-sinking to the PCB, while vias outside of the pads limit the current path to the top of the PCB trace and have worse heat-sinking capability when placed under the part (see Figure 4 and Figure 5). The ACSEVB-CB5 includes in-pad vias and is recommended to improve thermal performance.
NOTE: Designs with in-pad vias provides better thermal performance than without in-pad vias. The ACSEVB-CB5 uses in-pad vias.
The thermal capacity of the CB package should be verified by the end user in application-specific conditions. The maximum junction temperature, TJ(max) (165℃), should not be exceeded. The temperature measured at the top of the package closely approximates the temperature of the die.
SCHEMATIC
LAYOUT
The CB current sensor evaluation board features test points that allow the current-sensor integrated current-loop resistance to be measured directly from the evaluation board. The voltage-drop sensing is routed in the first internal layer (as to not reduce the isolation specification of the package). As a consequence, the voltage drop includes the parasitic resistance of the vias between the top layer and the first interior layer.
BILL OF MATERIALS
Components listed are based on the typical application circuit given in the respective device datasheet.
Table 1: Evaluation Board Bill of Materials
CB-PACKAGE [1] ASSEMBLY VARIANT
RELATED LINKS AND APPLICATION SUPPORT
Table 2: Related Documentation and Application Support
REVISION HISTORY
Copyright 2023, Allegro MicroSystems.
Allegro MicroSystems 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 MicroSystems 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.
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