Rollout of 5G is now well underway, with coverage on track for one third of the world’s population by 2025, according to the GSMA [1]. Major cell phone manufacturers have launched 5G-enabled phones, which will please those wanting to stream data and videos at up to the theoretical 50Gb/s maximum speed, and worldwide 5G subscriptions are forecast to reach 1.3bn by 2023, according to Statista [2].
However, 5G is much more than faster smartphones – it underpins the technology behind
artificial intelligence, cloud computing,
autonomous vehicles, the
internet of things (IoT),
smart cities and
industry, and probably more yet-undreamed of applications. As a result, investment in new 5G infrastructure will be high, and network operators will be looking for the quickest possible return on what is projected by Statista to be 1.4 trillion dollars’ telecom services spent in 2021 alone.
5G may eventually work at over 70GHz
5G infrastructure is not simply an upgrade to 4G; by its nature, at peak performance, 5G uses higher frequencies, and coverage is less, so more cells are required. Three bands are available: low, mid, and high, with the majority of installations using mid-band at 2.5 – 3.7GHz, at speeds up to 900Mb/s. The low band uses similar frequencies to 4G with similar range and coverage, so it offers little extra benefit but may be used in low traffic areas to achieve basic but wide coverage quickly. High band, eventually working at over 70GHz, yields the fastest data rates, but coverage is very limited, perhaps 1.5km, so it is preferred for public areas such as arenas, markets, and conference centers. Traffic in these locations can be high, but base stations can be small and distributed around a restricted area with ‘beamforming’ techniques to provide good coverage.
Cells therefore fall into coverage categories ‘metro’, ’micro’, ‘pico’, and ‘femto’ with reducing power outputs and range, from a Multiple Input Multiple Output (MIMO) metro cell transmitting over 100W to a femto cell operating at milliwatt levels. The term ‘small cell’ is also used for the three smallest categories together. With the increased throughput and number of base stations, energy consumption is set to rise overall, with some reports predicting a doubling compared with 4G. As energy is a major cost to network operators (5% to 6% with 4G according to MTN consulting [3]), there is extreme pressure to increase efficiency of all elements in base station electronics.
Base stations have a range of digital and analoge electronics needing power
Other electronics in a base station is a mixture of low noise analog signalling and digital processing, using familiar components such as CPUs, FPGAs, SoC devices, ADCs, DACs, and more. These components require voltage rails that might range from +5V for a DAC down to sub 1V for a processor or FPGA and typically employ non-isolated point of load converters (PoLs) or ‘power modules’ to provide an accurate, low-noise voltage right at the load. Input voltage to the PoL may be a system 48V or more likely, a regulated ‘intermediate bus’ at typically 12V.
Isolated DC/DC converters and power modules in 5G base stations often operate in a difficult environment with potential temperature extremes, transients from lightning strikes and other equipment, high RF fields and all in the smallest enclosure at the lowest acquisition cost. Reliability is paramount to avoid unnecessary maintenance expenses and electrical efficiency must be high to keep energy costs low and the burden of heat generation on other components minimized.
Non-isolated power modules are also featured in the
RECOM portfolio with ultra-compact, high efficiency parts using the company’s ‘
3D Power Packaging®’ technologies.
Fig. 2: The RECOM RPX series power module is tiny but rated at up to 4A output
The RECOM
RPX-1.0 and
RPX-1.5 series have a minimal 3 x 5mm footprint in a low-profile QFN package. The part uses flip-chip technology for extremely high power density, with 1A or 1.5A rated output, adjustable from 0.8-30V, for input voltages from 4-36V. With only a slightly larger footprint (4 x 4.5mm), the
RPX-2.5 offers 2.5A output current. If component height is not so restricted, the
RPX-4.0 offers 4A output current in a compact 5 x 5.5 x 4.1mm package. All of these converters are complete with integrated inductors and full protection (UVLO, SCP, OCP, OTP), requiring only output voltage setting resistors and input and output capacitors to form complete power supplies.
