IC selection

[sbkenn]

Hi. I have been looking for a multi-phase (3 or 4) controller for a DC-DC application, which has SPI, I2C, or other serial interface so that I can control the duty cycle (PWM) and read back outpt voltage and current. I need the supply voltage to be 18-40v (with different inductors for the higher range), o/p 14-18v, and external switches for high current.

Does anyone know of a suitable device ?
Failing that, I will use a PIC.

Thanks
Shane

 

[LiteYear]

If I understand you correctly, it sounds like about 100 different microcontrollers will do. Many of them have multiple PWM outputs that can be used to drive the switching element in a DC-DC converter. SPI and I2C is pretty standard, so that doesn't narrow it down much. A PIC may do, as would an AVR, or an MCF from Freescale or an LPC from NXP. If you need to narrow your search, you'll need to find some other constraints!

 

[sbkenn]

Thanks for your input. I hope to find a DC-DC controller to do it, rather than programming a uC. There are a few devices that have 2-phase outputs, but that isn't really enough for 18V to energise the choke to the high energy transfer that I need. There are ones for computer PSU's, but they all seem to have parallel-input control, and the high power outputs are 2.7, 3.3, or a few, 5V. Very few have a serial port through which to progran the power/PWM characteristics or to read the output current/voltage back to a master controller/display. I could use a pair of 2-channel controllers, if I an find ones that facilitate synchronisation.
For this application, I want the power stuff in one place, with remote monitoring (Arduino or Pi) and variance of power transfer.

 

[LiteYear]

Ah okay. As I'm sure you've realised, you're working a fine line between standard off-the-shelf behaviour and full blown uC custom development! I think you're quickly going to exhaust what dedicated function chips can do, but I understand that even the simplest uC requires quite some configuration work.

Perhaps change your search from "DC-DC controller" to "DC-DC converter". Converters are single function chips - they have a certain Vin range and a certain Vout range, but for the most part you have control over the switching device and output inductor. Typically they're designed for fixed output voltage, variable output power, but if you want variable output voltage then you can indirectly control the duty cycle by using a variable resistance feedback circuit. For serial interface monitoring, add an ADC.

If you really want to go down the controller route, with direct control over the PWM, maybe look at the Texas Instruments motor drive chips. They're obviously designed for motor control rather than DC/DC, but the switching function is actually quite similar. Start with the DRV8307. You supply the PWM signal (from your Arduino/Pi) and it drives external FETs. Instead of arranging them in half bridge, arrange them in a three phase buck converter configuration (three output inductors feeding one output capacitor). There'll be a lot of details to sort out, but maybe it's a worthy route.

 

[IRstuff]

A SPI interface does not come for free. That overhead is generally high enough that you want to put something more useful that a brick with an absurdly tiny set of commands, for which someone has to program at least an FPGA to make it worthwhile

TTFN
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[sbkenn]

Thanks for that insight. I guess I will have to bite the bullet and go with a PIC, probably a 16F1614. I am WAY out of practice at that level, and never really was a programmer anyway. Good tools these days though, and looking at the CCS compiler/debugger.