42V Power Management ICs have a built-in window or battery voltage detection

42V Power Management ICs have a built-in window or battery voltage detection

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By Nick Flaherty

Microcontroller processors often require a precise power supply in order to operate properly. To improve the reliability of a design, additional power management ICs (PMICs) are used to check if the power supply operates within the narrow safety margins. If the supply voltage exceeds the safety margins, the microcontroller must be reset to prevent its operation from working improperly.

The R5116 and R5117 both have a 500mA voltage regulator and supervisory circuits embedded in a single package which saves valuable circuit board space and additional wiring between the components, providing the designer a cost effective solution with minimal external components. Target applications are devices with a direct 12 V battery connection, ECUs, Infotainment, Security System, Dashboard Systems, Remote Keyless Entry, Immobilizer, Gateway and ADAS Drive Safety Systems.

The main differences between the R5116 and R5117 are the supervisory circuits that provide an active low reset signal when the regulator output falls out of regulation or when the input voltage falls below a minimum.. The R5116 has a 500mA Voltage Regulator and monitors the output voltage for both over- and undervoltage, while the R5117 monitors both the input voltage and output voltage for undervoltage. The circuit monitoring the output voltage has an independent sense pin which can be connected to the regulator output or directly to the microcontroller supply voltage pin for improving the measurement accuracy. All settings for the output voltage and supervisory thresholds are internally fixed by laser trimming and have a high accuracy level, making the product suitable as a power source with high reliability.

The CMOS-based devices are robust enough to survive in harsh conditions, operating up to 42 V and even tolerates load dump surge peak voltages of 60 V with a duration of less than 200 ms. The minimum operating voltage starts at 3.5 V, which makes the products suitable to use even at severe cranking conditions. The product will be available in separate versions for the consumer, industrial and automotive markets with customised operating temperature ranges of -40 to 105°C, -50 to 125°C and -40 to 125°C. The automotive version is scheduled to become AEC-Q100 compliant soon.

The voltage regulator has a ripple rejection ratio of 70dB at 1kHz so that a change on the input or load results in only a small signature on the output voltage, preventing false supervisory signals, while the total current consumption is typically 25 to 35 µA in operation and 1.5 to 10 µA in standby by controlling the chip disable pin.

The outputs have an N-Channel open drain and require an external pull-up resistor to define its logic high state, each supervisory circuit has its own output and can be combined together or connected individually to the microcontroller. An external capacitor is used to specify the active reset period and power on reset time, it should be set long enough in order to reset the processor properly.

The devices have over-current protection, reducing the output current when overloaded, as well as short protection via an embedded fold-back short current limit circuit that detects a short circuit and decreases the output current to a safe level of 105 mA. After removing the short the regulator resumes to normal operation automatically. Thermal protection turns the regulator off when an over-temperature of 175°C is detected and allows it to resume normal operation as soon a temperature of 145°C is reached.

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