RoadTest: RoadTest Review the TI LMZ36002EVM
Author: Former Member
Evaluation Type: Evaluation Boards
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: LM22677
What were the biggest problems encountered?:
Hello, and welcome to my review of the LMZ36002 Evaluation Module. I will be comparing the LMZ36002 to the LM22677, which I have used in designs at work. Some things to take into account when reading this review are the fact that I am testing the LMZ36002 at home with limited equipment so most of my content will come from a comparison of features presented in the datasheets(I don't have an adjustable power supply or fancy scope.), and my experience with the LM22677 is limited to the 5V version, whereas the LMZ36002 is adjustable. Towards the end of my review I will explain how I modified my evaluation board to control the output voltage with a potentiometer like an adjustable bench-top power supply.
First off, I'd like to talk specifically about the evaluation board. This is an awesome evaluation board. There are plenty of test rings to hook scopes on that I wish I had better tools to take advantage of. There is a way to latch on to pretty much every signal used or generated by the power controller. Also, kind of funny, but you will notice someone mislabeled the input terminals on the silkscreen and they had to cover it with a printed label.
These are the main differences I noticed when comparing the datasheets for the two controllers. Now, what do they mean? Well, for starters, if you need >42V in or >2A out you are pretty limited on choices. The LMZ36002 has a maximum operating temperature that is 20°C lower than the LM22677, however it is more heat efficient, and has a lower maximum output current to begin with, so in most environments this will never be an issue. The LMZ36002 will also shut off if the output current goes over what it can supply or the controller reaches an unsafe temperature.This is a huge advantage over the LM22677 in many situations, as it prevents these events from permanently damaging the controller, and possibly the output device depending on the nature of the event. I personally tested the over-current feature with an adjustable current sink, and found that I could actually get a couple hundred milliamps over 2A, but it is much safer to assume you are limited to 2A in your application.
When I applied for this road test I wasn't planning on modifying it at all. I thought I'd just use it with the predetermined output values, and call it a day. I didn't think of how interesting and simple this would be until reading the datasheet after receiving the evaluation board. The discovery that made this so appealing is that the range in Rset values in the table on page 13 of the datasheet is roughly 10kΩ. I don't know about anyone else, but I had a couple 10kΩ pot(entiometer)s laying around waiting for a use. According to the table the lower the resistance the higher the output voltage, with the maximum being 7.5V. From this we get two great pieces of information: where we should tie in with the pot (We'll use the jumper pins for the 7.5V setting.), and which leads on the pot to use to ensure intuitive use (We'll use pins 2 and 3 of the pot, so that the resistance decreases and the output voltage increases as the knob is turned clockwise.). You can see my modifications in the attached images.
Things to consider: