Technical Article

Tiny Power Components for Wireless Charging, Step Down Conversion and “Always On” Devices

December 17, 2014 by Wolfgang Patelay

This article introduces Texas Instruments' smallest, lowest power linear battery charger and tiny, fully integrated DC/DC power module.

Texas Instruments used electronica 2014 in Munich to showcase its broad portfolio of new products corresponding to the slogan coming from the Jack Kilby Day “TI technology is fundamentally changing the way we live our lifes – from wireless charging to autonomous vehicles, from smart cities and factories of the future to concussion sensors and bionic eyes”. And power is needed in all of these areas- therefore this article describes the news in power management presented at the exhibition.

Delivering power management innovation for ultra-low power designs, Texas Instruments introduced the industry’s smallest, lowest power linear battery charger and a tiny, fully integrated DC/DC power module, which consumes only 360nA of quiescent current, to help extend battery run-time in wearable electronics, remote sensors and MSP430 microcontroller-based applications.

The new bq25100 single-cell Li-Ion charger comes in a 0.9-mm by 1.6-mm WCSP package, and achieves a solution half the size of existing charger solutions. The device supports input voltages up to 30 V, and allows accurate control of fast-charge currents as low as 10mA or as high as 250mA, and precise charge termination down to 1mA to support tiny Li-Ion coin batteries. It also can support a leakage current of less than 75nA to extend standby operation. Designers also can add wireless charging capability to small portable and wearable applications by pairing the bq51003 2.5-W, Qi-compliant wireless charging receiver with the bq25100 linear charger on the same board. The bq51003 is an advanced, integrated, receiver IC for wireless power transfer in portable applications.

The device provides the AC/DC power conversion while integrating the digital control required complying with the Qi v1.1 communication protocol. Together with the bq500210 transmitter controller, the bq51003 enables a complete contact-less power transfer system for a wireless power supply solution. By using near-field inductive power transfer, the receiver coil embedded in the portable device receives the power transmitted by the transmitter coil via mutually coupled inductors. The AC signal from the receiver coil is then rectified and regulated to be used as a power supply for down-system electronics. Global feedback is established from the secondary to the transmitter in order to stabilize the power transfer process via back-scatter modulation. This feedback is established by using the Qi v1.1 communication protocol supporting up to 2.5W applications. The device integrates a low-impedance full synchronous rectifier, low-dropout regulator, digital control, and accurate voltage and current loops.


The bq25100 is targeted for ultra low-power designs
Figure 1: The bq25100 is targeted for ultra low-power designs


Both devices are featured on the new design reference board TIDA00318 which is suitable for low power wearable device including a Qi compliant wireless receiver (bq51003) and ultra low current 1 cell Liion linear charger (bq25100). It features an ultra small size (5x15mm²) capable of low charging currents down to 10mA and up to 250mA with support of termination currents as low as 1mA. Current design is designed for 135mA charge current application.


Step-down converter modules

The new TPS82740A und TPS82740B step-down converter modules support 200mA output current with 95 percent conversion efficiency and consume only 360nA of quiescent current during active operation and 70nA during standby. The tiny modules rely on a fully integrated, 9-bump MicroSiP package, which incorporates a switching regulator, inductor and input/output capacitors to achieve a solution size of only 6.7mm2. The TPS82740 is according to TI the industry’s first step down converter module featuring typically 360nA quiescent current consumption.

This new DCS-Control based device extends the light load efficiency range below 10µA load currents. It supports output currents up to 200mA. The device operates from rechargeable Li-Ion batteries, Li-primary battery chemistries such as Li-SOCl2, Li-MnO2 and two or three cell alkaline batteries. The input voltage range up to 5.5V also allows operation from an USB port and thin-film solar modules. The output voltage is user selectable by three voltage select pins (VSEL), within a range from 1.8V to 2.5V (TPS82740A) and 2.6V to 3.3V (TPS82740B) in 100mV steps. The TPS82740 features low output voltage ripple and low noise.

Once the battery voltage comes close to the output voltage (close to 100% duty cycle), the device enters no ripple 100% mode operation preventing an increase of output voltage ripple. In this case the device stops switching and the output is connected to the input voltage. The integrated slew rate controlled load switch with a typical ON-resistance of 0.6Ù distributes the selected output voltage to a temporarily used sub-system.


Energy savings to “always-on” smart meters

Hundreds of millions of smart meters around the world continuously draw power from the grid to measure energy use and provide feedback to the utility. Even though meters consume relatively small amounts of power that is not charged to the customer, when you multiply the amount of energy needed to power the devices, it makes sense to minimize the energy consumed. Therefore Texas Instruments is expanding its portfolio of high-voltage power solutions for offline AC/DC designs and introduced a 700V switcher with the industry’s lowest quiescent current of less than 100µA – half the power consumption of existing solutions.

The UCC28880 controller integrates a 700V power MOSFET and high-voltage current source, increasing overall energy efficiency of “always-on” non-isolated power systems with output currents up to 100mA, such as smart meters, home automation equipment and white goods. The controller integrates the controller and a 700-V power MOSFET into one monolithic device. The device also integrates a high-voltage current source, enabling start up and operation directly from the rectified mains voltage. The low quiescent current of the device enables excellent efficiency. With the UCC28880 the most common converter topologies, such as buck, buck-boost and flyback can be built using a minimum number of external components. The UCC28880 incorporates a soft-start feature for controlled start up of the power stage which minimizes the stress on the power-stage components.


The UCC28880 high-voltage switcher delivers energy savings to “always-on” smart meters and home automation designs
Figure 2: The UCC28880 high-voltage switcher delivers energy savings to “always-on” smart meters and home automation designs


The circuit integrates a 700-V MOSFET, start-up current source and internal current sensing in a tiny 7-pin SO package size of 29.4mm2. Additionally, no external compensation is needed which further reduces component count and board space. High-voltage pins are segregated to one side of the package, which maximizes separation between low and high voltage pins. Along with current limit function, the controller inductor current runaway protection helps protect against under load short-circuit conditions to ensure design reliability. The device provides over-temperature protection with hysteretic re-start for safe operation. The high voltage switcher reduces system cost and minimizes the overall size of the power supply, while maintaining high efficiency and system performance.

An offline AC/DC reference design PMP8550 based on the UCC28880 enables designers to quickly design a low-cost, low-power non-isolated high-side buck converter with a total solution size of 38mm by 32mm by 22mm that supports13V, while generating up to 100mA of output current. The reference design features a buck converter with integrated switch and can be used in numerous industrial applications. The design’s schematic, CAD files and test results are available for download. The reference design uses the UCC28880 low power, low cost, off-line buck converter with integrated 700V MOSFET to generate a non-isolated 13V/120mA output from a universal AC line input. Thanks to its hysteretic mode, no loop compensation is needed reducing BOM count to 23 components producing a small single sided, double layer board which can be used in numerous industrial applications such as smart meters, home automation equipment and white goods.


New family of 36-V and 60-V converters

Also introduced were seven Simple Switcher regulators that simplify wide VIN synchronous power supply design and help engineers create energy-efficient, electromagnetic interference (EMI) compliant products. The easy-to-use LM43600/1/2/3 and LM46000/1/2 DC/DC converters feature an input voltage range of up to 60 V for high reliability in rugged systems, and 27mA of standby current that minimizes power consumption at light load. The unique synchronous power stage architecture reduces radiated emissions for EMC compliance in a variety of industrial, automotive and communications applications. Synchronous rectification with integrated high-side and low-side MOSFETs simplifies design while improving efficiency, EMI and solution size. Programmable switching frequency up to 2.2 MHz allows for smaller external components.


Simple Switcher DC/DC regulators enable quickly design energy-efficient, EMI-compliant systems
Figure 3: Simple Switcher DC/DC regulators enable quickly design energy-efficient, EMI-compliant systems


The LM43600, LM43601, LM43602 and LM43603 synchronous regulators support an input voltage range from 3.5V to 36V and generate output currents of up to 0.5A, 1A, 2A and 3A, respectively. The LM46000, LM46001 and LM46002 support an input of 3.5V to 60V and output currents of up to 0.5A, 1A and 2A. The converters integrate compensation, control features and MOSFETs to reduce the bill of material (BOM) by up to seven components. The 16-pin, 5-mm by 6.4-mm thermally enhanced HTSSOP package is pin- and footprint compatible across the product family and is scalable for reuse across various applications. EMI-optimized pin placement simplifies printed circuit board (PCB) layout for CISPR 22 class B EMC compliance. The regulators are fully supported in the Webench online design tool, helping designers generate, optimize and simulate a wide VIN design, and then export that design to a CAD program.


This article originally appeared in the Bodo’s Power Systems magazine.