Current sensing is a common requirement in all types of motors, power supplies, and power systems. For current sensing above 50A, there are relatively more factors to consider, such as heat dissipation, the footprint of the detection scheme, and the possible isolation voltage requirements. Traditional shunt resistors plus op amps may have large heat losses and may also have high requirements for the common mode range of op amps if they are detected on the high side; if there is a need for isolation, optocoupler devices must be added. For current transformers, they are large and prone to magnetic saturation problems.
The Hall current sensor chip with isolated integration and built-in small magnetic ring can effectively deal with these problems, providing users with miniaturized, high-precision, and easy-to-design solutions.
Product Introduction
Ch704 series products are isolated integrated current sensing chips developed by Eri for high-current sensing applications above 50A, which have the advantages of high accuracy, enhanced insulation withstand voltage, high reliability and low power consumption. The chip integrates a precision programmable linear Hall chip, a small polymagnetic ring, and a copper row with a 0.1m on-resistance to achieve +/-50A, +/-100A, +/-150A, +/-200A current sensing, and factory pre-programmed to measure up to 400A surge current. The internal low-offset, chopper-stabilized linear Hall chip combines a unique temperature compensation circuit design to achieve good temperature consistency over the ch704 over the full temperature range (-40°C to 150°C). The chip is calibrated for sensitivity and quiescent (zero-current) output voltage before leaving the factory, providing typical accuracy of ±1% over temperature.
Main parameters
Dielectric strength test voltage: 4800Vac
Basic isolation working voltage: 1187Vdc / 840Vac; reinforced insulation working voltage: 672Vdc / 475Vac
AEC-Q100 Automotive Grade Chip Certification (CH704A)
The output voltage is proportional to the current: +/- 50A, +/- 100A, +/-150A, +/- 200A
It can measure 200 ADc (85°C ambient temperature); up to 400A of inrush current
5V power supply, bandwidth 180kHz, response time
The internal integrated magnetic ring effectively resists stray magnetic field interference and residual magnetism
Operating temperature range: -40°C to 150°C
Scenarios
Automotive electronics: OBC, DC-DC, EPS motors, etc
Industrial control: uninterruptible power supply (UPS), welding machine / mobile communication equipment and other power supply power supply
High-power motors: balance car/unicycle controller, heat pump/ice machine, etc
Energy: such as process control, battery detection, energy measurement, etc
Application example 1 – UNinterruptible power supply UPS
In a UPS system, all power supplied to the load undergoes a dual conversion of rectifier/charger and inverter (i.e. AC-DC-AC). The rectifier floats the battery to keep it fully charged. When the limit is exceeded or the mains power is blackout, the UPS turns on the battery discharge work, and the inverter and battery are continuously put into power for the load. When the UPS internal fault or load current transient or artificially stop the inverter, the load can be switched to the bypass AC input without interruption (start bypass operation).
Hall current sensors are used to control the floating charge source to ensure that the battery is working properly. Ch704 is responsive (
Figure 3: Application of CH704 in UPS uninterruptible power supply systems
Application example 2 – Motor phase current sensing
The output torque control of the motor is the key to the motor control system. Taking the PMSM motor FOC control algorithm as an example, its output torque is the following formula. Among them, the red box out of the part is the three-phase current collected by the current sensor. The accuracy and delay of the sensor directly affect the calculation of torque accuracy.
For motors of different power, the magnitude of the phase current and the threshold of overcurrent detection are also different. Eri's different current sensor products can cover the range of 5A to thousands of amps (single-chip solutions or equipped with magnetic ring solutions). For 50-200A (or transient currents up to 400A), the CH704 can achieve a typical detection accuracy of 1% over the full temperature range, as well
Application example 3 – Automotive OBC, DCDC
The current sensing requirements on automotive OBC and DCDC systems are related to the specific OBC architecture and model. A typical OBC (shown in Figure 6) consists of multiple cascaded stages, including a power factor correction PFC, a DC-DC converter, secondary rectification, auxiliary power supplies, control, and drive circuitry. Both the PFC input (AC) and the OPC output (DC) require a current sensor chip. Currently popular OBC power ratings are 3.3kW, 6.6kW, 11kW and 22kW; depending on the design, it can be powered by single- or three-phase power supplies. Taking the 6.6kW single-phase 220V/30A AC power supply as an example, considering the overcurrent threshold of 2.5-3 times, the +/-100A specification of CH704 can be used to detect the PFC input; at the OBC output, considering the between 100 volts and 800V on the high-voltage DC bus, the DC current is not large, and the +/-50A specification of CH704 can be used.
Figure 6: Application of CH704 in automotive OBC, DC-DC
Pin definition and model
The CH704 is available in a 5-PIN CFF package with a pinout as shown in Figure 7 and operates from a single supply of 5V. Pins 4 and 5 are current sense, pins 3 and 2 represent output and ground, respectively, and pin 1 is the chip supply terminal. The CH704 series has a total of 8 product models, and the naming rules and specific models are shown in Figures 8 and 9.
Figure 7: CH704 pin distribution
Figure 8: CH704 model naming conventions
Figure 9: Ch704 model list