1.0A Step-down DC-DCs with Fast Transient Response
Torex Semiconductor Ltd. has developed the XC9257/XC9258 series of step-down synchronous dc-dc converters with an output current of 1.0A and Torex's unique HiSAT-COT (High-Speed circuit Architecture for Transients with Constant On Time) fast transient response control. Compared to regular COT control, Torex's HiSAT-COT control enables greater suppression of frequency fluctuations caused by the load and input voltage. The response speed is eight times faster than previous products, and the output voltage drop is reduced by 50%.
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. 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 designed 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 the existing series that are equipped with HiSAT-COT control, Torex’s lineup now consists of four products and six series.
Features of the new dc-dc converters include: 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; and Package size is 50% smaller than the previous IOUT=1.0A type and low ON resistance is achieved.
