Current Limit Click is a compact add-on board that contains a low-voltage, P-channel MOSFET power switch intended for high-side load switching applications. This board features the MAX890L, a low-resistance power switch with the adjustable, accurate current limit system, and thermal shutdown from Analog Devices. Its internal current-limiting circuitry protects the input supply against overload, while thermal protection limits power dissipation. The maximum current limit is 1.2A and can be programmed through a digital potentiometer MAX5401. The quiescent supply current has a low value of 10μA in the active state, while in its off state the supply current decreases to 0.1μA. This Click board™ is suitable for applications in some portable equipment, access bus slots, or with power supplies, protecting them in cases of a short circuit or other overload conditions.
Current Limit Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.
Current Limit Click is based on the MAX890L, a high-side low-resistance P-channel switch with the adjustable, accurate current limit system, and thermal shutdown from Analog Devices. The MAX890L limits the output current to a programmed level. When the output current is increased beyond the programmed current limit (1.2A), the current also increases through the internal replica amplifier along with the resistance applied on the SET pin. The current-limit error amplifier compares the voltage across the SET pin resistance to the internal +1.24V reference and regulates the current back to the lesser of the programmed limit (1.2A). This switch is not bidirectional, which means the input voltage must be higher than the output voltage.
The current-limit switch is virtually ubiquitous in system control, and provide a safe means for regulating the current delivered to a load circuit. It allows the load current to increase to a programmed limit but no higher. Typically, the current limit is a function of the voltage across an external resistor, and this voltage serves as the reference for an internal current-limiting amplifier. By replacing the resistor with a digital potentiometer, you can easily program the current limit as performed on this Click board™. For this purpose, the digital potentiometer MAX5401 from Analog Devices that communicates with the MCU via 3-Wire SPI serial interface is used to set the resistance on the SET pin of the MAX890L, and thus adjust the current limit for the switch.
The MAX890L provides an open-drain fault output with a red color LED, labeled as FAULT used to indicate when current reaches its limit or when the temperature exceeds +135°C. Besides the fault-indicator pin, the MAX890L also has an active-low Switch-On pin labeled as ON pin of the mikroBUS™ socket used to enable and turn the switch on.
This Click board™ is designed to be operated with both 3.3V and 5V logic voltage levels that can be selected via the VCC SEL jumper. Additionally, there is a possibility in this selection that as a source of logical voltage level, a voltage from an external input terminal in the range from 2.7 to 5.5V can be used. In this way, whether using a logic voltage level from mikroBUS™ or an external voltage supply, this allows for both 3.3V and 5V capable MCUs to use the SPI communication lines properly.
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