1.0A Step-down Synchronous DC/DC Converters with HiSAT-COT Fast Transient Response Control XC9257/XC9258 Series

May 22, 2015

TOREX SEMICONDUCTOR LTD. (Tokyo Japan: President, Tomoyuki Fujisaka, 6616: JASDAQ at Tokyo Stock Exchange) has developed a new series of 1.0A output, step-down, synchronous DC/DC converters equipped with Torex's unique HiSAT-COT fast transient response control.

The XC9257/XC9258 series are step-down synchronous DC/DC converters with an output current of 1.0A and Torex's unique HiSAT-COT fast transient response control ("HiSAT-COT control" below).

Compared to regular COT control, Torex's HiSAT-COT control enables greater suppression of frequency fluctuations caused by the load and input voltage (Fig. 1). The response speed is eight times faster than previous products, and the output voltage drop is reduced by 50% (Fig. 2).

PWM control (XC9257) or PWM/PFM auto switching control (XC9258) can be selected for the operation mode, and a fast response, low ripple, and high efficiency are obtained over the entire load range, from light loads to heavy loads.

Fig.1 Minimal frequency fluctuation is realized


Fig. 2 Load-transient response characteristics


The output voltage can be set internally to a value from 0.8V to 3.6V (±2.0%) in steps of 0.05V. The only external components used are a coil and capacitor, and a high-efficiency, stable power supply with an output current of 1.0A can be obtained. Oscillation frequencies are 1.2MHz and 6.0MHz, allowing selection of the optimum frequency for the application.

By stopping all circuits during standby, the quiescent current is reduced to 1.0μA or less. The soft start function starts the IC in a quick 0.30ms (TYP.). An internal UVLO (Under Voltage Lock Out) function forcibly shuts OFF the internal Pch MOS driver transistor when the input voltage drops to 2.0V or less. The B type includes a CL discharge function that discharges the output capacitor during standby.          
Packages are the standard SOT-25 and the ultra-small USP-6C (1.8 x 2.0 x h0.6mm), contributing to space saving during the design stage.  
These converters are ideal for various portable devices, as well as applications such as microprocessors where it is desirable to prevent malfunctioning.

With the addition of these two new series to our existing series that are equipped with HiSAT-COT control, our lineup now consists of four products and six series.  
We will continue to expand our lineup of products equipped with HiSAT-COT fast transient response control to meet market needs.

XC9257/XC9258 Series Features

  • Employs Torex's unique HiSAT-COT fast transient response control
  • Load-transient response is eight times faster than previous products, and output voltage drop is reduced by 50%
  • A 1005-size ceramic capacitor can be used
  • For the switching frequency, a 0.47μH inductor can be used with the 6.0MHz type
  • USP-6C package (1.8 x 2.0 x h0.6mm), output current of 1.0A is possible
  • Package size is 50% smaller than the previous IOUT=1.0A type and low ON resistance is achieved

See the details of XC9257 Series
See the details of XC9258 Series

Torex Semiconductor Ltd. is a leading provider of CMOS power management ICs targeted toward battery powered and energy efficient applications. Torex specializes in CMOS analog technology, with LDO voltage regulators, voltage detectors and DC/DC converters making up our core product offering.