Convertors cut PSU size, cost and complexity

Two switched-capacitor DC/DC convertor families from Texas Instruments give designers increased simplicity and small size for a wide variety of applications.

Two switched-capacitor DC/DC convertor families from Texas Instruments give designers increased simplicity and small size for a wide variety of applications including portable devices and PC peripherals.

The TPS6040x series of 60mA voltage inverters generate a negative output of any DC input voltage between 1.6 and 5.5V with a quiescent current of just 65uA (TPS60401).

The other family, the REG710 series of 30mA buck-boost convertors, delivers a fixed regulated output over a wide range of input voltages without the need for a linear voltage regulator.

Key specifications of the TPS6040x are its 60mA maximum output current and a conversion efficiency of up to 98%.

Despite its high current capability, the only external components required by the TPS60400 are three small ceramic capacitors with values as low as 1uF.

Unlike competitive parts, the TPS6040x needs no external Schottky diode to start under load; instead, an active Schottky diode is built in, reducing the overall inverter footprint to less than 51mm2.

The TPS6040x is available in three fixed-frequency versions - the 20kHz TPS60401, the 50kHz TPS60402 and the 250kHz TPS60403 - as well as the variable-frequency TPS60400, which keeps the operating current low and efficiency high over a wide range of loads.

Qualified for battery-powered products, the TPS6040x family provides the bias voltage in LCDs and GaAs power amplifiers as well as supplying the sensor voltage in portable instruments.

Configured as a rail-splitter, the TPS6040x can also deliver the bipolar voltages needed for use in medical and other instruments.

The second device, the REG710 switched-capacitor buck-boost convertor, maintains a fixed, regulated output voltage across an input voltage range of 1.8 to 5.5V.

Reducing system size and cost, the REG710 automatically steps up or down the input voltage to maintain the specified output, 2.5, 2.7, 3, 3.3 or 5V, eliminating the need for both a boost convertor and a linear or LDO regulator to perform the same task.

The REG710 is well suited for many applications including PC peripherals such as, PCMCIA and CardBus devices, SmartCard readers and CompactFlash cards and battery-powered handheld and portable equipment, such as cellular phones, barcode scanners, white LED drivers, GPS receivers, electronic games, personal digital assistants, notebook and portable computers.

To save power and extend battery life, the REG710 also employs pulse frequency operation that switches only when under load.

That way, the quiescent current is reduced to typically 65uA.

As the REG710 has a 1MHz switching frequency, it works with ceramic capacitors, eliminating the need for tantalum capacitors at the output - or anywhere else on the device - saving space and cost.

Compared with ceramics, tantalum capacitors are larger and more expensive and typically have higher equivalent series resistance and inductance values which compromises noise performance.

In contrast to inductive solutions, the REG710 needs no inductors or diodes, precluding the need to calculate inductance values or contend with magnetic shielding to suppress EMI.

The REG710 includes overtemperature and overcurrent protection and automatically limits inrush current to protect the system and further suppress EMI while maintaining design simplicity.

The TPS6040x is available in a five-pin SOT23 package.

The REG710 comes in a six-pin SOT23 package.

Prices start at $0.60 each for the TPS6040x family and $0.89 each for the REG710, both in quantities of 1000.

A universal evaluation board TPS60400EVM-178 is also now available for the TPS6040x product family.

The TPS6040x family is pin-compatible with the following devices: MAX828, MAX870, ADM8828, SP6828/6829, ICL828, LM828, TC828, TC829.

The REG710 family is pin-compatible with the LTC1754 product family.

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