Bernie Blegen
Vice President and Chief Financial Officer at Monolithic Power Systems
Thanks, Jen. For the full year, 2022, MPS achieved record revenue of $1.79 billion, growing 48.5% from the prior year. This is despite industry-wide supply chain capacity constraints. This performance represented consistent execution against our strategies and having more Tier one customers recognize MPS for advanced technologies, product quality and excellent customer support. Here are a few highlights from 2022. We introduced a new product line of isolated power modules for applications exceeding one kilowatt with a fully integrated controller, isolator and power devices. Our initial revenue ramp for this highly integrated and reliable solution is targeted for 2024.
These modules are critical building blocks for power management applications for data centers, EVs plug-in traction inverters, EV chargers, solar power, wind turbines, battery power storage and other industrial applications. Our products are designed to set the industry standard for these critical system-level applications. MPS's first advanced data converter products for high precision industrial and medical applications were made commercially available during 2022, and we expect to have an initial revenue ramp in 2023. We continue to diversify our global footprint with expansion of our R&D centers supply chain partnerships and facilities outside of China to better match our resource distribution with our customers' geographic demand profile. With our global presence, we believe MPS is in a strong position to support our customers worldwide.
Turning to our full year 2022 revenue by market segment compared with 2021. Enterprise Data revenue was up 116.1%, Storage and computing revenue up 76.8%, Communication revenue up 53.2%, Automotive revenue up 46.8%, Industrial revenue, up 18.6% and consumer revenue, up 13.2%, demonstrating broad-based full year 2022 revenue improvements. Full year 2022 enterprise data revenue grew $135.1 million over the prior year to $251.4 million. This 116.1% increase is primarily due to higher sales of our power management solutions for cloud-based CPU and GPU server applications. Enterprise data revenue represented 14.0% of MPS's total revenue in 2022 compared with 9.6% in 2021. Storage and computing revenue for 2022 grew $196.7 million over the prior year to $452.6 million. This 76.8% increase primarily resulted from strong sales growth for storage applications and enterprise notebooks.
Storage and computing revenue represented 25.3% of MPS's total revenue in 2022 compared with 21.2% in 2021. Communications revenue grew $87.4 million to $251.5 million. This 53.2% improvement reflected higher sales of products for both 5G and satellite communications infrastructure applications. Communications revenue represented 14.0% of our 2022 revenue compared with 13.6% in 2021. Automotive revenue grew $95.7 million to $300.0 million in 2022. This 46.8% year-over-year gain primarily represented increased sales of our highly integrated applications supporting automated driver assistance systems, the digital cockpit and connectivity. Automotive revenue represented 16.7% of MPS's full year 2022 revenue compared with 16.9% in 2021.
Industrial revenue grew $34.4 million to $218.2 million in 2022. This 18.6% year-over-year increase primarily reflected higher sales in applications for smart meters and industrial automation. Industrial revenue represented 12.2% of MPS's full year 2022 revenue compared with 15.3% in 2021. Consumer revenue grew $37.2 million to $319.5 million in 2022. This 13.2% year-over-year increase primarily reflected increased product sales for home appliances and smart TVs. Consumer revenue represented 17.8% of MPS's full year 2022 revenue compared with 23.4% in 2021. Let's talk about the general business conditions. During our Q3 '22 earnings call, we highlighted that customers were becoming more concerned with near-term business conditions and order patterns might oscillate in the near future.
As a result of this change in ordering patterns, we indicated that our inventory levels would likely catch up to our target of 180 to 200 days and possibly be higher in the near term. During the quarter, ordering patterns stabilized as customers requested pushouts -- customer requested pushouts slowed. When this is positive, customers' orders are still trending below historic norms. In our Q4 '22 inventory is above our target levels. As a result, we remain cautious about near-term business conditions. We also believe MPS can swiftly adapt to market changes as we have done so successfully during similar macroeconomic changes in the past. Switching to Q4. MPS had a record fourth quarter with revenue of $460.0 million, down 7.1% from revenue generated in the third quarter of 2022, but up 36.7% from the comparable quarter of 2021.
On a year-over-year base comparison, by market segment, fourth quarter 2022 revenue for automotive grew 72.8%, Enterprise Data revenue increased 69.0%. Storage and computing revenue grew 55.0%, Communications revenue grew 40.1%, and industrial revenue grew 13.3%, while consumer revenue decreased 20.1%. Fourth quarter 2022 GAAP gross margin was 58.2%, down 50 basis points from third quarter 2022 with 60 basis points higher than the fourth quarter of 2021. Our GAAP operating income was $136.9 million compared to $151.9 million reported in the third quarter of 2022 and $78.6 million reported in the fourth quarter of 2021. Fourth quarter 2022 non-GAAP gross margin was 58.5%, 50 basis points below the third quarter of 2022, but 60 basis points higher than the fourth quarter of 2021.
The year-over-year expansion in fourth quarter non-GAAP gross margin was largely due to a shift in sales mix favoring high-value greenfield products and operational efficiencies, which more than offset higher product input costs. Our non-GAAP operating income was $174.1 million compared to $193.7 million reported in the prior quarter and $102.0 million reported in the fourth quarter of 2021. Let's review our operating expenses. Our GAAP operating expenses were $130.9 million in the fourth quarter compared with $139.0 million in the third quarter of 2022, and $115.3 million in the fourth quarter of 2021. Our non-GAAP fourth quarter 2022 operating expenses were $94.8 million, down from the $98.4 million we spent in the third quarter of 2022 and up from the $83.0 million reported in the fourth quarter of 2021.
On both a GAAP and a non-GAAP basis, fourth quarter 2022 litigation expense was $3.2 million compared with a $2.1 million in Q3 2022 and a $420,000 credit balance in Q4 2021. The fourth quarter 2021 litigation credit reflected in IP settlement in a of a legal retainer. The differences between GAAP and non-GAAP operating expenses for the quarters discussed here are primarily stock compensation expense and income or loss from an unfunded deferred compensation plan. Fourth quarter 2022 stock compensation expense, including $1.0 million charged cost of goods sold was $35.3 million compared with $43.0 million recorded in the third quarter of 2022. The quarter-over-quarter change in stock compensation expense reflected the change in planned vesting assumptions. Switching to the bottom line.
Fourth quarter 2022 GAAP net income was $119.1 million or $2.45 per fully diluted share compared with $2.57 per share in the third quarter of 2022 and $1.51 per share in the fourth quarter of 2021. Q4 2022 non-GAAP net income was $154.0 million or $3.17 per fully diluted share compared with $3.53 per share in the third quarter of 2022 and $2.12 per share in the fourth quarter of 2021. Fully diluted shares outstanding at the end of Q4 2022 were 48.5 million. Now let's look at the balance sheet. As of December 31, 2022, cash, cash equivalents and investments totaled $739.6 million compared to $738.1 million at the end of the third quarter of 2022. For fourth quarter -- for the fourth quarter of 2022, MPS generated operating cash flow of about $52.2 million compared with Q3 2022 operating cash flow consumed of $18.2 million.
Fourth quarter 2022 capital spending totaled $12.8 million. Accounts receivable ended the fourth quarter of 2022 at $182.7 million or 36 days of sales outstanding compared with the $153.4 million or 28 days of sales outstanding reported at the end of the third quarter of 2022 and the $104.8 million or 28 days reported at the end of the fourth quarter of 2021. Our internal inventories at the end of the fourth quarter of 2022 were $447.3 million, up from $397.4 million at the end of the third quarter of 2022. Calculated on a basis consistent with our past practice. And as you can see on the webinar video, days of inventory rose to 212 days at the end of Q4 2022 from the 167 days at the end of the third quarter of 2022. Historically, we have calculated days of inventory on hand as a function of the current quarter revenue.
We believe comparing current inventory levels with the following quarters revenue provides a better economic match. On this basis, again, you can see days of inventory increased to 214 days at the end of the fourth quarter of 2022 from 188 days at the end of the third quarter of 2022. I would now like to turn to our Q1 2023 outlook. We are forecasting Q1 2023 revenue in the range of $440 million to $460 million. We also expect the following: GAAP gross margin in the range of 57.4% to 58.0%, non-GAAP gross margin in the range of 57.7% to 58.3%, total stock-based compensation expense of $40.2 million to $42.2 million, including approximately $1.2 million that would be charged to cost of goods sold. GAAP R&D and SG&A expenses, including litigation expenses between $135.1 million and $139.1 million.
Non-GAAP R&D and SG&A expense to be in the range of $96.1 million to $98.1 million. This estimate excludes stock compensation expense but includes litigation expense. Beginning with the Q1 2023 outlook, MPS will no longer separately forecast litigation expenses. Interest income is expected to be in the range from $1.8 million to $2.2 million before foreign exchange gains or losses and charitable contributions. The non-GAAP tax rate for Q1 2023 will be 12.5%. The non-GAAP tax rate remains unchanged from 2022 as there have not been any material changes in tax regulations. Fully diluted shares to be in the range of $48.2 million to 49.2 million shares.
Finally, I'm pleased to announce a 33% increase in our quarterly dividend to $1 per share from $0.75 per share for stockholders record as of March 31, 2023. In conclusion, while we remain cautious about near-term business conditions, we believe MPS can swiftly adapt to market changes and take advantage of current environment to focus on business development and investing in infrastructure necessary to support long-term growth.
I'll now open the webinar up for questions.
