Adjustable Voltage Regulator with Digital Interface???.........

[Smokey]

I'm looking for a switching voltage regulator with an adjustable output that I can control digitally.  Something like I2C is perfect.  SPI is acceptable.  1Wire if I had to.  A DAC controlling a regulator with a feedback pin is an absolute last resort.

Specs:
>15V input voltage
Up to 5.5V output voltage
>=500mA output current
Cheap as possible.
No BGA if possible.

Hits?

[ajb]

Have you looked at PMICs meant to be used with microprocessors (core voltage regs, etc)?  That's where you're most likely to find a digital interface, but not sure if you'll hit your output voltage spec in that application space. 

[jitter]

Yeah, something similar to TI's TPS65233.

[Smokey]

That TPS65233 looks killer, and not bad at $2.74USD in 1s...
But the output voltage is only 13.1V to 13.7V or 18.2V to 19V.  Can't get it down to around 5V.

[Euphyllia]

  A DAC controlling a regulator with a feedback pin is an absolute last resort.

Why the kibosh on this? Seems like a low-passed PWM output summed into the feedback pin would work fine unless you have some other requirements.

[technix]

You can also cook up your own regulator by controlling a Buck converter using a microcontroller with PWM output and ADC input, preferrably using a few spare PWM and ADC pins on your main application processor to reduce part count.

For the simplest design you can use the traditional Buck circuit with a PMOS, a Schottky diode and an L/C filter. If your MCU supports complimentary PWM with dead-zone configuration you can use some advanced control mechanisms like synchronous NMOS buck converter (using two NMOS, a gate driver chip like IR2110 and a L/C filter).

[tszaboo]

So something, like LTC3883?
The hard part, your requirement is too small current. Most of these power supplies with I2C interface are for high power/current, with discrete FETs and stuff. I would take a look at Linear technology. Also, On semi is huge in the computing business for core voltage regulators.

[technix]

At least to me, for small-scale projects, I often use ATtiny85 as PMIC. Those small microcontrollers are often cheaper than those dedicated digital PMICs (usually requires external MOSFETs anyway) and have a 64MHz timer with bipolar PWM mode which allows me to use smaller inductors and synchronous rectifying if I find the need to do so.