Realization of Simple High Voltage Current Detection

High Voltage Tolerance, Flexibility and Accuracy

LT6100 and LTC6101 are high voltage, accurate, high voltage side current detection amplifiers. Their simple architecture allows flexibility and ease of use, while their careful design makes them reliable and robust.

Key features include high power range, user configurable gain, low input current, high PSRR, and low misalignment voltage. These features make LT6100 and LTC6101 the perfect choice for precise industrial and automotive sensing applications and current overload protection circuits.

The LT6100 operates at a voltage of up to 48V, is simpler to use than LTC6101, requires little external components, absorbs very little power, and can withstand abnormal conditions such as separate input, power outage and battery reversal.

LTC6101 is the faster of the two devices, can work at a voltage of up to 70V, is more flexible, and has an external resistor for setting gain. Both devices can be packaged in a variety of small packages.

Working principle of current detection

There are two common methods for current detection. One method utilizes the principle of magnetism, which is constructed by coupling a magnetic field to a coil or Hall-effect sensor using a magnetic conductive material. There is no need to plug directly into the circuit under test, and coil pickup inherently does not provide any DC information (but it is possible to use a special "magnetic flux gate" technology), and Hall sensors often lack accuracy and sensitivity for most DC measurements.

Another method is to place a known "detection" resistance on the load path, which results in a small voltage drop proportional to the load current. Generally speaking, the preferred connection method for detecting resistors is to place them on the power side of the circuit so that the common grounding method can be maintained and load faults can be detected. In the case of positive power potentials, this connection is often referred to as a "high voltage side" detection configuration, as shown in Figure 1. This means that from the point of view of the detection amplifier, the detection voltage is a small difference signal on a large common-mode signal, which puts forward unique requirements for the implementation scheme to maintain accuracy and dynamic range.

Traditional "self-contained" solutions use operational amplifiers or instrumentation amplifiers, but these amplifiers often have limitations in the voltage range at which they operate and/or require the use of many additional components to perform voltage transformations to produce a geographically benchmarked read-out signal. LT6100 and LTC6101 are much better and simpler solutions to meet most high voltage side current detection requirements.

Pay close attention to the source of current detection error

As with all sensor designs, there are several potential sources of error that need to be considered. The accuracy of the circuit largely depends on the known resistance value of the detecting resistor. The detection resistor itself defines tolerances and temperature dependencies that cause errors. Stray resistance or large dI/dt loops in the measurement path can also cause errors to increase. It is important to correctly implement Kelvin connections to the detection resistor to minimize these effects by 1.

In addition to detecting resistors, the most notable source of error is detecting the voltage misalignment of the amplifier, which creates a level-independent uncertainty in the measurement. This is particularly important for maintaining accuracy at current levels that are far below the design values. In some applications, it is desirable to remove the static component of the item by calibration (e.g., using software), but this method is sometimes not feasible.

Another source of error to consider is the tolerances of all resistors, which may be required in setting the scale factor. This affects the full scale uncertainty along with the detection resistor and Kelvin connection tolerance. For LT6100, the regulator resistors are integrated on the chip, so the tolerance is defined and described in the product data table specification. For LTC6101, the adjustment accuracy is strictly set by the resistor selected by the user, thus allowing optimizations for specific requirements...