Nexperia Announces LED Drivers in DFN Packages with Side-Wettable FlanksOctober 29, 2020 by Gary Elinoff
The AEC-Q101-qualified devices save up to 90% PCB space and improve reliability.
The new LED drivers feature an output current of up to 250 mA with a maximum supply voltage of 75 Volts.
Nexperia’s new range of LED drivers is housed in the leadless, space-saving DFN2020D-6 (SOT1118D) package. Critically, the new units feature side-wettable flanks (SWF) which serve to make it simple to employ the use of AOI (automated optical inspection).
Nexperia’s new series of LED Drivers. Image courtesy of Nexperia.
According to Nexperia, this is the first time LED drivers have been available in this beneficial package.
The company notes that it presently offers a wide range LED drivers in packages such as the popular and leaded SOT223, with the new units offering equivalent performance while saving up to 90% of the board space.
What are Side-Wettable Flanks?
Nexperia’s Hans-Jürgen Funke spelled it out in an article he did for All About Circuits entitled, “Side-Wettable Flanks Enable AOI on Leadless SMD (DFN) Packages.”
In summary, quad flat no-lead packages are popular because they eliminate leads, and, as such, they save board space. But, as Funke points out, because the solder connection is only underneath the plastic body of the package, the soundness of the connection can only be inspected via a costly x-ray processes, and not through the use of far less expensive AOI.
The solution, as described in detail in the article, involves covering the sides of the contact pads with plated tin in the same electro-galvanic plating step as used for the bottom pads. A full tin-plated side-wettable flanks (SWF) means that the complete side pad surface is wetted with solder during the reflow soldering process.
Image courtesy of Nexperia and All About Circuits
As illustrated above, the success of the soldering step is easily verified by optical inspection. This is especially important to automotive customers.
Additionally, devices with side-wettable flanks offer more resistance to shear forces, and can also endure more board flexing without the entire structure failing.
Commented Frank Matschullat, product group manager at Nexperia: “The new DFN2020D-packaged parts with SWF address the concerns of various sectors – size, performance, ruggedness – so they are a perfect match for many diverse applications in general lighting, white goods and automotive. Nexperia is committed to delivering the industry’s broadest discrete portfolio in DFN technology, so introducing LED drivers in this rugged, space-saving package is a natural step. However, parts are also available in leaded SMD styles so customers can choose which to use.”
Members of the New Family of LED Drivers
Members of the new family are described in this Nexperia Product page. All the new LED drivers come in SWF packages sized at 2 x 2 x 0.65 mm.
The NCR320PAS and the NCR321PAS provide output currents up to 250 mA, while the NCR421PAS and the NCR420PAS are 150 mA devices. The devices can be used in parallel if more output current is needed, and all units sport NPN transistors.
The NCR421PAS and the NCR321PAS can accept a digital PWM input frequency of up to 10kHz. They can both be used for PWM dimming by driving the VEN pin, as illustrated below.
Modified image courtesy of Nexperia
The full output current is controlled via the external resistor attached between REXT and ground.
The units are aimed largely at automotive applications, are AEQ-Q100 qualified and they operate over a temperature range of -55 to 150℃.