Avoid riding the brakes when driving downhill. You may have been experiencing brake fade.

Does your transmission allow you to shift into a lower gear (like a tiptronic mode?

What does your owner’s manual say about precautions when driving downhill?

Ya your van is heavier than some cars, so it picks up more speed you definitely don't want to ride your foot on the brake. That heats them up. Try using a lower gear or tap the brakes for a few seconds at a time. 

Riding the brake down a long incline creates a ton of friction like they're supposed to, but friction produces heat. The heat is normally dissipated faster than it accumulates, but going down huge hills, it doesn't dissipate fast enough for you to ride the brake all the way down. The heat builds up in the calipers and drums, and it causes built-up water in brake fluid, and the fluid itself to boil. That's what causes the spongy brake, you're no longer compressing an incompressible fluid, you're compressing fluid and compressible gas, making the pedal spongy. The brake pads also gas off where they contact the rotors, forcing them away from the rotors.

Look at your gear indicator on your dash. Below D there should be a series of numbers, like 2 and 1, or something like L, or even a Sport mode. If you have Sport mode, put the selector in sport mode and manually downshift it into either the lowest gear the computer will allow, or the next higher gear to keep the RPMs a little lower. That will use the engine to slow the car down instead of just the brakes. The low gear forces the engine RPMs up, and when the throttle is closed (foot off the gas) that slows the car down. It won't hurt your car at all to do this. The computer will stop you from over-revving the engine. 

With the advent of disc brakes drivers became less familiar with the phenomenon of brake fade. The old drum brakes would retain heat and cook really fast under hard braking (like going downhill), to the point where you'd lose brakes completely relying on them to maintain control. (If you've driven in the mountains you may have seen "truck escape" ramps for large trucks whose brakes have faded away going downhill.) Although brake fade is less common today it can still happen.

Another issue is people tend not to change brake fluid regularly. The fluid absorbs moisture over time and lowers the boiling point which can cause you can lose hydraulic pressure under extreme conditions.

Yes, I tend to ride the brakes down the hill everyday (I live up the hill), vs. using engine braking.  I replaced the brake pads a few months ago.  However, I haven't replaced the rotors in awhile so could that cause my brake fade?  I didn't feel any shaking going downhill.

Yes, I believe I have the tiptronic mode on my automatic transmission.  I have to give that a try but my hill is pretty steep so even with the car in lower gear, it picks up speed down the hill.

Braking seemed fine on top of the hill, it was towards the bottom of the hill where I started smelling the burning smell.  There was a car in front of me so the pressed the brake harder but it felt spongy and didn't feel like it did anything.  Luckily, I wasn't going too fast by then so I was able to stop.  Didn't feel comfortable driving further so I went back home uphill.  

Still had slight spongy feeling heading back but didn't feel normal.  I'm assuming something happened when I was going downhill riding the brake.