Ultra-Precise, Current-Sense Amplifier

 

 

This circuit uses Texas Instruments' ultra-precise current-sense amp, which can measure voltage drops across shunt resistors over a wide common-mode range from 2.7 V to 120 V. The amp is available in a highly space-efficient SC-70 package with a PCB footprint of 2.0 mm x 2.1 mm. It achieves ultra-precise current measurement accuracy due to its ultra-low offset voltage of ±12 µV (maximum), a small gain error of ±0.1% (maximum), and a high DC CMRR of 160 dB.

Designed for DC current measurement and high-speed applications (such as fast overcurrent protection), this amp has a high bandwidth of 1 MHz (at a gain of 20 V/V) and an 85 dB AC CMRR (at 50 kHz). It operates from a single 2.7 V to 20 V supply, drawing a 370 µA supply current (typical). The amp is available with five gain options including 20 V/V, 50 V/V, 100 V/V, 200 V/V, and 500 V/V. Its low offset of the zero-drift architecture enables current-sensing with low ohmic shunts over the extended operating temperature range of -40°C to +125°C.

Driving a Bicolor LED from a Single Output Pin

 

This circuit showcases the control of a bi-colour LED from a single output pin using two PNP transistors. You can access the Java Script simulation link here: 

                                   👉  https://tinyurl.com/22y3w9er                                  

The circuit comprises two NPN transistors for switching, one bi-colour LED, two resistors for base current control, another two resistors for collector current setting for each transistor, and two voltage sources. The first voltage source at the top outputs 24V to drive the LEDs, while the second voltage source supplies 3.3V at the base of the transistors to simulate logic control output from microcontrollers.

In the OFF position of the switch, both transistors are in the OFF state, and the LED on the right side is ON via a 10k resistor with an LED driving current of 2.2mA. When the switch is ON, both transistors are in the ON state, driving the LED on the left side, while the other LED is switched off because the transistor on the right side is on, pulling down the LED anode voltage.

Protecting Microcontroller Input TINA (TI) Simulation

Over Current Protection at Output Stage/ Pins

 

The purpose of this circuit is to restrict the output current to less than 20mA, and this limit can be adjusted using resistors R1 and R8. Furthermore, the circuit also can disconnect the input/output when the output short circuits to a high positive or negative voltage by limiting the current. 

Additionally, the diode D1, located at the output and the 5V0 pin, serves to suppress the kick-back voltage from an inductive load. This occurs when the drivers are deactivated (stop sinking) and the stored energy in the coils causes a reverse current to flow into the coil supply through the kick-back diode.

How to use MOSFET for Hide Side Switching

 

I've crafted a circuit designed for high-voltage (up to 100V) and high-current (up to 33.6A) applications, specifically for switching loads on the high side. The carefully selected P-Channel MOSFET, Q1, boasts low ON resistance. To safeguard against exceeding the maximum gate-source voltage (VGS), I've incorporated R1 and R2. Another option involves including a Zener diode across the Gate and Source. In addition, a small signal N-Channel MOSFET, Q2, effectively controls the ON/OFF switching of the N-Channel MOSFET. When the ON/OFF control is low, Q2 remains OFF. Conversely, when it's high, Q2 activates, thereby reducing the P-Channel gate voltage via R2 and effectively limiting the current.

Overvoltage Protection

 

This circuit monitors the input voltage (VIN) and safeguards the output voltage using a series-connected transistor (Q14). In the event of over-voltage conditions, Q14B is activated, which in turn causes Q14A to disconnect the output from VIN. The desired overvoltage limit is established by the combination of D10 and the voltage across the base emitter (VBE) of Q14. For instance, if the required cutout voltage is 12V, the Zener voltage of D10 should be 11.4V (12V - 0.6V). 

You can view a simulation of the above circuit in the video below.