Test Procedure

This test procedure is compilation of what I found helpful when testing, and things I wish I had done.

• Check for power shorts! Any paths from VCC to GND are very bad. Check with a mult-imeter on the ohmmeter setting or the continuity setting.
• After using the continuity setting to check for shorts from VCC to GND, switch the multi-meter to the diode test setting. Having the positive lead on the positive battery connection spot on the board, and the negative on GND should result in 0L. However, switch the placement of the leads so that the positive lead is on GND should result in about a 0.56 V drop. This is good if you see these two results - as it shows the presence of the body diode of the LODRV MOSFET in the correct orientation.
• Triple check mosfet orientation
• Triple check which are the positive and negative terminals of the battery, as reversing them when plugging them into the board could result in a fried circuit board.
• Check solar panel output - should at least be greater than 9.5V.
• Check battery voltage - needs to be less than 8.4V to experience any type of charging
• Attach the solar panel to the charger circuit - watch for any shorts, and be aware of the temperature of the mosfets and charger IC. If they get hot very quickly, there's a good chance that they shorted somehow - and you should proceed to verify if that component is indeed fried.
• If nothing gets hot while the solar panel is attached, proceed to take voltage readings at the following places: Vsolar, VCC, VtoHIDRV, VMPPSET, VTS, VREF, VREGN, VBTST, VHIDRV (look at with oscilloscope), VLODRV (look at with oscilloscope), VFB, VSRN, VSRP, VPH (look at with oscilloscope). A good indicator of whether your IC is working or not is by looking at the VREF and VREGN pins. These are set voltages coming from the IC. They should be 3.3V and 6V respectively. If they are not near those voltages, first check to make sure you're probing the right pins, and if you are, then there's a good chance that the IC is damaged and you'll have to replace it.
• If all of the above test points check out, then proceed to attach the battery (again, make sure you connect the positive and negative leads of the battery to the correct points on the board - otherwise circuit damage to the IC and mosfets is very probable).
• With the battery attached, monitor for any component's temperature increasing more than it should. With the battery attached, the STAT1 LED should turn on to indicate a charging in progress status.
• If the temperature seems to be stable on the IC and no visible shorts have occurred, then proceed to test all the points that were tested before previously.
• Next, proceed to testing thoroughly the DC-DC buck converter to look for characteristics similar to those noted in the datasheet. For instance, some interesting points to compare would be the gate and source of each mosfet to see when it is turning on and off. If there was some way to monitor the current flow through the inductor, that would be ideal. I may consider building in a way to do that in a future board revision.
• Another interesting thing to observe might be the output voltage ripple.
• Lastly, checking the charge of the battery! The battery should be charging at 0.5A, so periodically checking the voltage of the battery is a good way to see if the circuit is doing what it should be.
• Celebrate if it's working! If it's not working, check out the Issues Tab for things I have encountered and discussed with an application engineer at Texas Instruments.