30-V/1.2-A PWM step down DC/DC converter offers optimal circuit efficiency
The R1245 features a new option to select from four different operating frequencies which means the frequency that best fits the application can be selected, resulting in optimal circuit efficiency.
The enhanced Feedback voltage accuracy leads to better output voltage stability, and when compared to similar competitive products, the R1245 has a better transient response performance and lower switching noise.
The R1245 can operate up to 30 V and the adjustable output voltage can be set from 0.8 V to 24 V with two external resistors. By using the recommended components as mentioned in the reference circuit, a maximum of 1.2 A can be obtained from the power supply.
Latched or fold-back type current limit types are available for the R1245. The latched current limit circuit is triggered when the Lx current exceeds the maximum level and when the feedback voltage decreases below nominal voltage. If this condition remains for more than 4 ms the chip is set into the off mode. To resume normal operation, the cause of the short- or over-current needs to be removed and the chip re-started.
The fold-back current limit is triggered when the feedback voltage decreases below 70% of its nominal voltage, then the oscillator frequency decreases to keep the current limit level to a lower short voltage. In the fold-back condition, the R1245 remains active and recovers automatically to normal operation when the cause of the short- or over-current is removed. For stable operation, small ceramic capacitors with low ESR can be used.
Availability
As well as the standard SOT-23-6W package for the R1245, smaller and larger packages are now available.
Visit Ricoh Europe at www.ricoh.com/LSI/
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