MCU voltage regulator

Remember I'm a newbie for electronics and have only just started using PIC and Atmel microcontrollers in my simple learning projects, but a question. Why don't microcontrollers have a voltage regulator built into the chip? I have some old A3141 hall sensors that can take an input voltage of up to 24 volts because it has an internal voltage regulator, keeping the parts count down, But if I use a microcontroller in the same circuit I have to add the regulator and caps, so an MCU with a built in regulator would be very handy. There must be a valid reason why it's not so, it's just that I can't think what it could be.

why Honda Civic has no build in 10ft trailer? Because it make chip much more expensive and least versatile. Avr controllers van wok on voltages from 2 to 5 volts. Higher voltage - faster speed.

why Honda Civic has build in 10ft trailer?

LOL!

Lot's of IC's do not have built in voltage regulators! Actually it's quite rare to see chips that can handle voltages above 5V, apart from some CMOS logic IC's like gates or counters and analog circuits.

Most micro controllers, RAM, ROM, FLASH and most sensors that have a digital communication interface like UART, SPI or I2C, all of these usually have a 5V, 3.3V or even less maximum voltage rating.

Why? I don't know! It's probably something about the internal construction of the IC and higher voltage normally also means higher power consumption.

Why? I don't know! It's probably something about the internal construction of the IC and higher voltage normally also means higher power consumption.

Lots of reasons. ..heating dissipation for one and the need to control temperature rise.

kangyunmei: Remember I'm a newbie for electronics and have only just started using PIC and Atmel microcontrollers in my simple learning projects, but a question. Why don't microcontrollers have a voltage regulator built into the chip?

The In laws need jobs to.

Those simple microcontrollers does not need well stabilized voltage. It can run from a coin cell battery or 2 (3) alkaline/NiMH cells without any regulator at all. When you add a regulator you often add it for another part of the system or because you have too high supply voltage. But there is no one-size-fits-all regulator. Does it need to tolerate high input voltage? Is it required to be LDO? Or switching one? Step up, down or both? What current is needed?