Feature Story
How does Richtek get 3.5A out of a SOT-23-6 package?
Learn how Richtek's latest ACOT® Buck converters support up to 3.5A output from a tiny SOT-23-6 package.
Our flip-chip on lead (FCOL) packaging minimizes the thermal and electrical resistance of a SOT-23-6 package.
Introducing the
RT7294/RT7295, 2.5A/3.5A ACOT® Buck converters in
flip-chip SOT-23-6 package, the latest addition to 18V Richtek
ACOT® family, ideal for Set Top Boxes, industrial and commercial low power systems, computer peripherals and LCD Monitors and TVs
The key advantages of a flip-chip SOT-23-6 package are better electrical performance and improved thermal capabilities compared to conventional wire-bonded products
Conventional wire-bond vs. flip-chip on lead in SOT-23-6 package
Package profile :
| Wire-bond |
Flip-chip on lead |
 |
 |
| The silicon die is glued to the center (GND) lead, and the die electrical connections are wired to the lead frame pins via bonding wires, which are typically 25-38um gold or copper wires. |
The topside of silicon die is mounted via pillar bonding to the lead frame providing both the thermal and electrical connections directly from silicon die to the lead frame. |
FCOL technical benefits :
1. Better electrical performance
| Wire-bond |
Flip-chip on lead |
|
The thin wires add resistance, inductance and stray capacitance to critical circuit nodes, which reduces the performance of high frequency switching converters. |
The short interconnect length of pillar bonding delivers significantly less resistance, inductance and stray capacitance, which minimizing I2R and switching losses while reducing waste heat.
|
2. Improved thermal capabilities
Wire-bond
Thermal image |
Flip-chip on lead
Thermal image |
Simulation
 |
Simulation
 |
Actual measurement
 |
Actual measurement
 |
|
The bonding wires are poor heat conductors so most of the potential heat transfer of the pins is lost. Heat transfer is mostly from the back side of the die through adhesive to the center ground pin, causing a hot spot on the center pin.
|
All pins are acting as small heat sinks and can be used for efficient cooling, so there is more heat transfer from package to PCB, resulting in lower die temperature.
|
Tips for FCOL PCB layout :
By adding some extra copper to all pins in PCB layout, the thermal resistance from junction to ambient can be significantly improved. With vias to inner layers, thermal conduction can be further enhanced, and θJA as low as 55⁰C/W is possible.
Lower conduction losses together with better thermal properties of FCOL SOT-23 packages make it possible to squeeze more power out of these small packages.
For more information, and application notes please check ACOT® landing page and video.
New Products
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26mΩ/19mΩ Low RDS(ON) , flexible solution with Soft-Start, PGOOD and external compensation. Avoid sensitive frequencies by synchronizing to an external clock.
RT8509/A (2A/4.5A) 4.5A, 1.2MHz, 2.8V-14Vin, 24Vout Boost converter
1.2MHz Fsw allows for smaller components and the high current limit permits high duty-factors/boost voltage ratios. Ideal for applications generating 24V from 5V or 12V system voltages.
RT7285/RT7294/RT7295 1.5A/2.5A/3.5A, 500kHz ACOT® Buck converters (Advanced Constant On Time) in SOT-23-6
Ultra fast transient response, constant average frequency, and stable with all-ceramic low ESR output capacitors for Set Top Boxes and applications requiring small footprint.
RT8575 4.2V-24Vin, 60Vout, 4 string WLED driver with boost regulator
150kHz-500kHz adjustable Fsw, 50mA-150mA programmable LED current per channel with 120Hz - 1kHz true PWM dimming control. Ideal for backlighting and multi LED string general lighting applications.
Did you know…?
- Richtek has filed 788 patents.
- Richtek was recognized as 'Best Partners' by ASUS, Panasonic and other global electronic product manufacturers.
- Richtek has introduced over 600 new products since 1998.
- Richtek products are all Green/RoHS compliant, REACH compliant and Halogen Free.