Half Bridge Driver (IR2184) Question - Page 1
Forum section: electronics / beginners

author: TheAdmiralty
author_rank: Contributor
timestamp: October 30, 2016, 10:52:42 pm
content: Evening, everyone!Back with another quick question on power delivery. I'm working on making a simple power delivery board for two brushed DC motors that will draw a significant amount of current; suitable monolithic full bridges are prohibitively expensive, and so I've been shopping around for a simple high+low side driver IC.IR's IR21xx series, specifically the IR2184, seems to fit the bill perfectly but I've got a question for anyone who's implemented it before. This is going into a mobile platform with battery power anywhere between +12V and +24V depending on the configuration. I've got +5V and +3V3 rails regulated for all of the digital control and MCU stuff, and would like to avoid having a third +10V rail if at all possible. The IR2184 recommends +10V for its low-side supply voltage, and -0.3V as an absolute things-start-igniting minimum. In short, has anyone operated this particular IC on +5V? I'm asking because the FETs I've specced can provide more than enough current at Vgs = 5V with minimal power dissipation, but I'm not sure whether the +10V rating on the IR2184 is more of a safety margin for any diode drops and/or the fact that most FETs do perform best at higher thresholds than what I'm working with, or if it actually just doesn't function at lower voltages.Any thoughts? I figured I'd ask around here first before I order in a small bag of various drivers for validation.Much appreciated!-M

author: Ammar
author_rank: Regular Contributor
timestamp: October 31, 2016, 01:36:34 am
content: How much current are we talking?Also, if I understand correctly you intend to drive the motors off a 5v supply?

author: TheAdmiralty
author_rank: Contributor
timestamp: October 31, 2016, 02:12:07 am
content: I'm looking at around 20-30A rated dead stall current on each motor; regular operation will only be on the order of a few amps, but the system's going to be set up in a way that it should be able to drive the motors at full stall current for some period of time before either a thermal interlock breaks the circuit or the MCU decides there's a problem and kills output.Not quite, the motors will be driven by either +12V or +24V straight from the battery. What I meant is that I need a single control unit which will be able to handle either of these two configurations; I have a board already half laid out with +5V readily accessible... I could pack a local +10V regulator in there, but I'm shooting for as few components as possible. My main question is whether the 'recommended' 10V to 20V Vccshown inthis datasheetis a hard limit, or if it's a case of the mfr taking into account typical applications and speccing accordingly.Sincethisis the FET I'm hoping to use for switching, 5V VGSwould be enough voltage for what I'm using it for, even with a diode drop, but I don't know if the IR2184 will work on that supply. Hopefully that clears things up a bit?Have done a lot of embedded work but am relatively new to power stuff, just trying to get the hang of things.

author: Ammar
author_rank: Regular Contributor
timestamp: October 31, 2016, 03:01:03 am
content: Okay, so it looks like it will come down to timing.The absolute maximum ratings suggest that what you want to do is fine.However, the recommended operating conditions have a caveat that says if you want the timing diagrams specified in the data sheet to apply, you need to meet the recommended operating conditions.This makes sense since turning switches on and off in this IC means charging and discharging capacitances. If you want to know more, read about bootstrap drivers. You want the difference in potential in the recommended operating conditions to allow for quicker charging/discharging and hence, quicker switching.Your best bet would be to try one out and see if it works and meets your timing requirements for switching.