HT4278
Features
• Output voltage tolerance ≤ ± 2%, 4% • Very low current consumption
• Separated reset and watchdog output
• Low-drop voltage
• Watchdog
• Adjustable watchdog activating threshold
• Adjustable reset threshold
• Overtemperature protection
• Reverse polarity protection
• Short-circuit proof
• Suitable for use in automotive electronics
• Wide temperature range
Functional Description
The HT4278 is a monolithic integrated low-drop fixed-voltage regulator which can supply loads up to 200 mA. The device is available in the 14-SOP-225 package. It is designed to supply microprocessor systems under the severe conditions of automotive applications and therefore equipped with additional protection functions against over load, short circuit and over temperature. Of course the HT4278 can also be used in other applications where a stabilized voltage is required.
An input voltage VI in the range of 6V ≤ VI ≤ 28V is regulated to VQ,nom = 5 V with an
accuracy of ± 2%.
An input voltage VI in the range of 28V ≤ VI ≤ 45 V is regulated to VQ,nom = 5 V with an
accuracy of ± 4%.
The device operates in the wide temperature range of Tj = – 40 to 12 5 °C.
Two additional features are implemented in the HT4278 a load dependent watchdog
function as well as a sophisticated reset function including power on reset, under voltage reset, adjustable reset delay time and adjustable reset switching threshold. The watchdog function monitors the microcontroller, including time base failures. In case of a missing rising edge within a certain pulse repetition time the watchdog output is set to LOW. Programming of the max. repetition time can be done easily by an external reset delay capacitor. To prevent a reset in case of missing pulses, the watchdog output WO is separate from the reset output RO for the HT4278