What is GaN SiP?

GaN SiP (Gallium Nitride System in Package) is a device that integrates the following into a single package:

GaN HEMT (Gallium Nitride Field-Effect Transistor: High-speed, low-loss switching element)

• Driver circuit (circuit that drives the switch)

• Digital control IC (integrated circuit that controls power supply operation)

Traditionally, these components were designed individually, but in SiP, they are integrated into a single package in an optimized state.

This allows designers to focus on "how to use it" rather than "how to drive it."

[Figure: Internal Block Diagram of GaN SiP (RRW221xx)]

Source: https://www.renesas.com/ja/document/dst/rrw2211x-datasheet?r=25611341

The value that multimode control brings

At the heart of the RRW221x series is MMC (Multi Mode Control).

By integrating PWM, PFM, and Burst control, the switching frequency and current are optimized according to the load conditions.

This is not simply a matter of switching between operating modes such as PWM/PFM/Burst, but rather a control system that automatically transitions to the optimal mode according to the load and input/output conditions, and further maintains switching (valley turn-on) at the lowest point of Vds generated during resonance.

Therefore, unlike typical forced PWM, it does not suffer losses under light loads, and unlike simple PFM, it is easier to avoid the problem of dropping into the audible range with DPWM*. By reducing reliance on burst control, it is possible to optimize noise, EMI, and standby power in a better balance than with light load control. Furthermore, in the RRW2211x, this control also leads to the realization of zero standby power, which will be explained next.

*Deep-PWM: When the load is light and the frequency approaches the audible range, it maintains a fixed frequency of approximately 28kHz to avoid audible noise.

Implementation of Zero Standby Power (ZSP) technology

The RRW2211x features a unique control system that keeps standby power consumption below 5mW.

For example, if the USB Power Delivery cable is unplugged and no load is connected, the system will work in conjunction with the secondary control IC (such as the iW780) to stop almost all functional blocks and transition to sleep mode.

However, it does not completely shut down; monitoring continues at a very low frequency, minimizing response delays when a load is connected.

This helps to reduce standby power consumption.

About ActiveStartup

The RRW2210x and RRW2211x have an ASU (Active Start Up) pin.

This mechanism separates the power supply paths for startup and steady-state operation. It is implemented by adding a depletion-type NFET between the VCC and HV lines in the primary control circuit example below. A depletion-type NFET is an FET that remains ON even when Vgs (gate-source voltage) is 0V.

The operation is as follows:

1. During startup: Power is supplied from the high-voltage line via a resistor, and the IC starts up.
2. Steady state: Depletion NFET is turned off and power is supplied from the auxiliary winding.

This means:

- Fast startup (depending on the series resistor connected to the FET)

- Low loss during steady state

This makes it possible to achieve both simultaneously.

[Figure: Example of primary circuit diagram]

Multifunctional sensing using V_SENSE

One of the distinctive features of this series is the advanced use of the V_SENSE pin.

This pin not only detects the output voltage, but can also detect the input voltage and resonant state through the auxiliary winding.

In other words, with 1 pin

Output voltage detection

• Valley detection (switching optimization)

- Input voltage estimation (brownout detection)

This achieves the above and also contributes to reducing the amount of peripheral circuitry.

Gate drive that maximizes GaN characteristics

GaN's strength lies in its high-speed switching capabilities, but it also presents challenges.

The challenge is that high electron mobility leads to large current and voltage fluctuations, potentially causing noise and malfunctions due to parasitic components.

Renesas GaN-SiP products are designed to address these issues.

- Fine-tuning of the gate drive terminal and gate terminal using external resistors via external wiring on the IC.

(Adjustable with the resistor between the DRV-GATE pins in the circuit diagram below)

- Internal pull-up resistor adjustment via CFG pin (RRW2210x only)

All of these methods adjust the current value used to drive the gate of the GaN-FET.

By changing the current flowing through the gate using internal or external resistance, the time it takes for charge to accumulate in the gate changes, and as a result, the rise and fall times of the switching can be adjusted.

Furthermore, with the RRW2210x, while the internal resistance can be adjusted using the CS/CFG pins shown in the circuit diagram below, it is also possible to add a function that automatically controls the internal resistance value.

These gate drive control flexibilitys enable both high-speed operation and EMI suppression.

[Figure: Example of gate drive circuit configuration]

Source: https://www.renesas.com/ja/document/dst/rrw2210x-datasheet?r=25611409

 

The difference between PSR and SSR

Renesas GaN-SiPs offer two control methods.

PSR(Primary Side Regulation)

- No photocoupler or shunt regulator required

• Simple circuit

SSR(Secondary Side Regulation)

• High-precision control

-High speed response

- Higher frequency than PSR enables small size and high capacity.

PSR (Power Supply Responder) is a control method that estimates the output from primary-side information, making it easy to reduce the number of components and suitable for low cost and miniaturization. On the other hand, compared to SSR (Server-Side Responder), which directly monitors the output, its accuracy and response to load fluctuations are limited.

Therefore, PSR is suitable for applications where low capacity, cost, and footprint are important, such as home appliances, small industrial equipment, and IoT devices.

On the other hand, SSRs directly monitor and control the output voltage and current on the secondary side, enabling high precision and fast response. Their high-frequency operation also offers advantages in terms of miniaturization and higher capacitance.

Therefore, SSR is suitable for applications that require high efficiency and miniaturization, such as TVs, large home appliances, fast chargers, and communication equipment.

[Figure: Comparison diagram of PSR (left) vs SSR (right) configurations]

Image source (left): PSR (left) EBC10298_RRW21111+IW673_65W Adapter Design V1.0.pdf

Source:

EBC10298 - 65W, 24V Primary Side Restriction (PSR) GaN SiP Evaluation Board | Renesas documentation "EBC10298 65W Adapter Design Files"

Image source: SSR (right) EBC10320_RRW22101+RRW43010_100W 1124 Adapter Design V1.pdf

Source:

EBC10320 - 100W, 24V Secondary Side Control (SSR) GaN-SiP Evaluation Board | Renesas The document "EBC10320 100W Adapter Design Files”

Summary: GaN is shifting from a "performance" tool to a "design tool."

The value of GaN SiP goes beyond just being small and highly efficient.
Rather, the essence is,

The goal is to reduce the overall burden of the design process.

From the perspective of actual design work, the following benefits can be expected in particular:

Design stage

- Parameter adjustment becomes more flexible

- Circuit design becomes simpler

Evaluation stage

- Reduces rework in EMI testing.

- Temperature evaluation becomes more stable

Mass production stage

- Reduces variations in operation

- Quality problems will decrease.

These factors combined allow designers to focus on more essential considerations. In future power supply design, the key decision-making criterion will shift from "Should we use GaN?" to "Which GaN will make the design process easier?"

A promising option is GaN SiP.

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