IC Builds Small Yet Efficient Buck Converters for Industrial Handhelds and Consumer Devices

Aug 3, 2005 3:48 PM
By David Morrison, Editor, PETech

Leveraging its new LBC7 analog process technology, Texas Instruments (TI) has announced a 1.5-A dc-dc stepdown converter that supports input voltages ranging from 3.1 V to 17 V. The TPS6211x synchronous, stepdown converter with integrated FETs achieves 95% efficiency to extend battery life in industrial handhelds, portable test equipment and consumer devices. Housed in a 4-mm × 4-mm QFN, the TPS6211x achieves high efficiency over a wide load current range by entering a power-saving pulse-frequency modulation (PFM) mode at light load currents. The converter is offered with either an adjustable output voltage ranging from 16 V down to 1.2 V (TPS62110), a fixed output of 3.3 V (TPS62111) or a fixed output of 5 V (TPS62112).

This device is distinguished by a unique combination of features and performance specifications. This converter is a complete synchronous converter in a very small package. Unlike other competing devices, this converter requires no external diode. Moreover, most competitive parts are said to require larger passives to complete the converter design (see the figure). The TPS6211x achieves high efficiency while switching at 1 MHz.

The quiescent current for the TPS6211x is 20 µA typ. Although there are other devices on the market with I_Q in the 10-µA to 25-µA range, many comparable products specify I_Q in the milliamp range. In addition, TI’s converter can be placed in a shutdown mode in which current consumption drops to less than 2 µA.

Another key specification is the TPS6211x’s wide input-voltage range, which permits operation from 2- and 3-cell Li-ion batteries, as would be found in various portable applications. The wide input range also makes the converter suitable for operation from 12-V or 15-V power rails in nonportable applications. In addition, the 1.5-A output rating delivers higher power levels than some competing devices.

The TPS6211x also can be synchronized to an external clock signal between 0.8 MHz and 1.4 MHz. For even lower noise operation, the converter can operate in a PWM-only mode. For more information on the TPS6211x, see www.ti.com/sc05147.

The TPS6211x is based on TI’s new LBC7 high-performance analog process. The advanced BiCMOS process allows TI to create power conversion ICs with the industry’s lowest R_DS(ON) and the capability for future devices to handle 30-V supply voltages. In addition, the company believes the LBC7 process will make it possible to raise the current rating on the TPS6211x to 3 A using a somewhat larger die that still fits within the same 4-mm × 4-mm QFN package.

TI also plans to exploit the new process to offer integrated dc-dc buck and boost converters with significantly faster switching speeds and increased logic density of more than 22,000 gates per square millimeter.

TI complements the TPS6211x with its new dc-dc boost inverter in a 3-mm × 3-mm QFN, the TPS63700. The inverter provides an 800-mA typical switch current limit and converts an input of 2.7 V to 5.5 V to an output voltage as low as -15 V. Coupling the device with a small 4.7-µH inductor results in a very small inverting dc-dc footprint. The TPS63700 is suitable for precision amplifiers and data converters used in industrial applications that require both positive and negative power supply voltages. The inverter’s small size and capabilities also allow it to support portable LCD displays, CCDs and organic LED (OLED) displays. For more information on the TPS63700, see www.ti.com/sc05147b.

Available now, the TPS6211x is priced at $2.50 each in quantities of 1000 units. The TPS63700 inverter is currently sampling with volume production expected in September.

With the addition of a few small, external passives, the TPS6211x creates a complete buck converter that operates from inputs as high as 17 V.

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