RoadTest: SIMPLE SWITCHER®: LM46002PWP EVM by TI
Evaluation Type: Independent Products
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?: null
What were the biggest problems encountered?: The manual of the EVM board did not contain any detailed information. The Board pin outs are not clearly marked.
This Roadtest is not complete yet. I am waiting for my test results which hopefully I can retrieve by next week.
The LM46002 SIMPLE SWITCHER is a high efficient buck regulator which can step down dc-dc voltage and supply a load current of 2A from a input voltage varying from 3.5 V to 65 V. The evaluation module that is roadtested in this review is capable of supplying 1-28V output voltage and the switching frequency can be changed from 200 kHz to 2200 kHz depending on the application requirements. The biggest concern in the design of this evaluation module seems to be avoiding electromagnetic interference (EMI).
Changing the Output Voltage
One the main concern of anyone who purchases this module will be changing the output voltage from the default 3.3 V to the desired value. It is obvious that we expect to get an output voltage between 1 and 28 Volts because the board description says that it can supply a variable voltage in that range.
The key is the feedback pin (FB) in the LM460002. This is because the voltage of the internal reference voltage is set according to the voltage applied on the FB pin. So it is pretty straight forward process of changing the resisters that build the voltage divider for the FB pin.
So this divider gives us the simple equation
VFB =VOUT * RFBB / (RFBT + RFBB)
Which we can use to calculate the required values for RFBB and RFBT. VFB is set at 1.011V. The recommended values for the RFBT is between 10kΩ and 100 kΩ as for the user manual. But in the case of this evaluation board, it comes with 1MΩ resistor for RFBT and 432kΩ for RFBB for obvious reasons described in the manual. For more details you might want to read the user manual because it contains a much more detailed description.
For my application I needed to change the RFBT to 249kΩ, which give the output voltage of 5V.
The values in the Table 2 from LM46002 can be used to get the desired output voltage at a desired switching frequency. And it also contains a worked out example that can be followed to understand settings. Further the WEBENCH® software can be used to calculate the desired values of the resistors, capacitors and inductors to get the required results. It is really easy to use and highly recommended.
The Card Edge Connector
When testing this board it is always easy to use a connector that can be easily detachable but can used get all of the required connections out from the board. As this board comes this can be connected to a 20 position 2 sided card edge connector
The connections are as following
For the application of this board my idea was to use it as a power supply in an environment with high level of electromagnetic interference since it is the main purpose of this evaluation board's design. The environment that I chose was a grid substation that actually contains a lot interference. main reasons for this is high current carrying cables and surges. So usually the equipment that we use there are not directly plugged in to the supply. We usually use voltage stabilizers and surge protectors before connecting them. But even then the output voltages changes due to the electromagnetic interference. To see the whether this board stood up to the task I used fault recorder to record the output voltage if it changed beyond the predefined variation level.
This part is to be completed later !
Useful Links and Other Information
These documents and links contain a lot of useful information about applying this EVM board and it’s applications. The manuals are attached as pdf files.
Simple Switcher main web site
Card edge connector