In many cases, there is a clause that allows for bigger amounts, so long as there is a 21 day notice. Unlike a bank line of credit, there is no interest due on a Drip. But there are hurdles. Here, an investor gets a security that can be converted into common stock. This security may be a preferred stock, which gets higher priority than common stockholders if there is a liquidation.
Some convertibles have reset provision.
In other words, the conversion price falls as the stock price falls. This can set the stage for a death spiral. For example, the investor can short the stock, as the reset price falls, and then swap the convertibles at the reduced price. This can be extremely lucrative. Unfortunately, the stock price will get pummeled.