The debt pays 6.0% annually and can be converted to APEN shares at $3.25 apiece, with Austin, Texas-based Apollo able to force the conversion of the unsecured debentures.
Apollo said it plans to use the proceeds for working capital and general corporate purposes.
Craig-Hallum Capital Group was the placement agent for the offering, the company said.
Last month, Apollo posted second-quarter results that beat analysts’ expectations for sales but missed on earnings.
The company reported a net loss of -$8.8 million, or -40¢ per share, on sales of $14.3 million for the three months ended June 30. Analysts on Wall Street were looking for losses per share of -38¢ on sales of $12.9 million.