RENESAS Technology has introduced the RNA50C27AUS, the industry's first reset IC that incorporates a core power-on control function, for microcontrollers that operate core logic circuits from a 1.8V power supply and input/output (I/O) peripheral circuits from a 3.3V supply.
Available through Hitachi , the new reset IC eliminates the complicated power-on timing aspect of power-supply system design needed to prevent these dual-power-supply microcontrollers from going into a runaway (fault) condition.
It simplifies the electronics by eliminating the external transistor switch and timing circuit that would be necessary if a traditional reset IC was used. Also, the RNA50C27AUS helps ensure reliable system operation by monitoring both supply voltages and generating a reset if either one falls below a critical level.
Finally, the device eases system design by providing a control function for turning the core power supply on or off.
To ensure proper operation, the 1.8V and 3.3V supplies of dual-power-supply microcontrollers must be turned on in the proper sequence - first the 1.8V supply, then the 3.3V supply - and then only when those supply voltages are above critical thresholds.
Further, after a system reset is initiated, the release time of that signal must be at least a certain minimum length, a time delay that is determined by the application.
The new RNA50C27AUS reset IC delivers all these capabilities and more. The device's external resistor and capacitor determine the reset signal release time. The reset output signal has fast (10ns) rise and fall times.
To accommodate different applications, an open-drain output or CMOS output can be selected for the reset output signal. Using the CMOS output allows a direct connection to a microcontroller's reset pin.
The precision with which the dual-voltage reset IC detects abnormalities in the voltages of the core and I/O power supplies is ±1 percent (maximum) - the same high degree of precision provided by conventional reset ICs.
Package for the RNA50C27AUS is an 8-pin SSOP-8 with a small body size (2.2mm x 2.4mm, excluding pins) and lead-free specifications.