The LT8418 Built-in Circuit (IC), a latest launch by ADI on the APEC in California, is a novel part that options hanging similarities to the output stage used within the newly launched GaN driving DC-DC controller ICs, particularly, LTC7890 and LTC7891.
Distinctive Options of LT8418
The LT8418 IC stands out for its high-side and low-side outputs which have distinct pull-up and pull-down connections situated on the IC bundle channels. This construction permits the usage of extra resistors for fine-tuning the GaN transistor’s turn-on and turn-off instances independently. This break up gate drivers design is meant to permit clients to customise the on-off behaviour to successfully tackle management and adaptability points.
Output Present Sourcing and Sinking
For each high-side and low-side drive, output present sourcing is achieved by way of a 0.6Ω pull-up (4A peak), whereas sinking is facilitated by means of a 0.2Ω (8A peak). This design ensures an optimized and balanced output present stream.
Over-voltage Safety
Given the sensitivity of GaN gates to over-voltage, which may trigger injury barely above the suggested drive voltage, the high-side bootstrap shouldn’t be by way of a standard diode, however as a substitute, a ‘smart-switch’. This good bootstrap change contains energy switches that may totally handle bootstrap charging or blocking, thus effectively stopping overcharging and potential injury.
Bootstrap Swap and Beneath-voltage Lock-out Safety
The bootstrap change prompts to start out charging the bootstrap capacitor when the underside change is turned on and the switching node voltage nears the bottom degree. The change has a typical on-resistance of 6Ω, dropping 0.6V when 100mA is flowing into the bootstrap capacitor. Moreover, bootstrap under-voltage lock-out safety is included to forestall the GaN transistors from turning on with inadequate drive voltage, tripping at 3.1V and clearing at 3.35V (250mV hysteresis).
Bundle and Pin Configuration
The LT8418 is housed in a 1.7 x 1.7mm WLCSP BGA bundle, with two internally related pads for the high-side output. Considered one of these pads is designed for offering a low-inductance path to the bootstrap capacitor. The Vcc pin can also be doubled, one for the ability rail and one for the IC’s decoupling capacitor. Two enter pins are offered, one for the high-side GaN PWM waveform and one other for the low-side.
Issues and Purposes
Concerning the LT8418 functions, ADI has acknowledged that it may be configured into synchronous half-bridge, full-bridge topologies, or buck, increase, and buck-boost topologies. Nonetheless, it is very important be aware that no anti-over-lap safety is offered. Subsequently, if each inputs are set to logic ‘1’, each GaN output transistors can be turned on concurrently inflicting excessive present stream. Thus, a considerate strategy should be utilized to the enter interface to keep away from a doable shoot-through situation.
In abstract, the LT8418 is a promising addition to the world of ICs, particularly designed for GaN driving DC-DC controller ICs. With its distinctive options and functionalities, it’s poised to supply nice flexibility and management to customers. It’s certainly a step ahead within the realm of expertise and innovation.
