Holtek HT77S1x New High-efficiency Step-up Voltage DC/DC Devices

02/25/2010

Following the successful release of Holtek’s high efficiency step-up DC/DC converter devices, namely the HT77xx and HT77xxA series, Holtek is now delighted to announce a further DC/DC converter device range. This new device range, the HT77S1x series offers the benefits of even higher efficiencies and larger current output capabilities.

The HT77S1x devices, using CMOS technology and PFM design techniques, can achieve DC/DC conversion efficiencies of up to 91%, an important feature in its ability to extend the battery life for power sensitive battery powered applications. In possessing a very low start-up voltage of only 0.7V, these devices are especially suitable for use in applications which are powered using a single Alkaline, Lithium-ion or Ni-MH cell. With their low output voltage ripple and excellent noise characteristics, the devices can also extend their usage into RF module applications. Regarding requirements for external components, because of the control driven synchronous rectifier design structure, the devices only require a single external inductor and capacitor to implement a full step-up DC/DC conversion circuit. As a result, the external diode which is required for the HT77xx (A) series is not required for this new device range. In addition to its fundamental DC/DC step up conversion function, the HT77S1x also contains a voltage detect function which can monitor the system voltage.

The new HT77S1x series subdivides into two categories according to their current drive capabilities. These are NMOS current drive limits of 1A current limit for the HT77S10 and 0.65A for the HT77S11. When the input voltage is 2V and output voltage is 3.3V, the HT77S10 can supply 350mA output current while the HT77S11 can supply 300mA. The fixed 3.3V and 5V voltage outputs of the HT77S1x are obtained by connecting the FB pin to either VOUT or GND. Other output voltages in a range of 1.8V~5.5V can be generated by connecting an external resistor divider circuit.

Regarding packaging, the devices are available in MSOP8 and SOP8 package types providing a range of options for small portable applications.