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Ricoh Semiconductor Support Centre launches the R1245 Series, 30V / 1.2A PWM Step Down DCDC Converter
Building on the popularity of the predecessor R1240 Step Down DCDC Converter, the R1245 features a new option to select from four different operating frequencies. This 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 30V and the adjustable output voltage can be set from 0.8V to 24V with two external resistors. By using the recommended components as mentioned in the reference circuit, a maximum of 1.2A 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 4ms the chip is set into the off mode. To resume normal operation, the cause of the shortor 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.
As well as the standard SOT-23-6W package for the R1245, smaller and larger packages are now available.
- Operating Voltage: Min. 4.5V to Max. 30V
- Output Voltage: (adjustable) 0.8V to 24V
- Feedback Voltage: Typ. 0.8V ±1.0%
- Lx Peak Current Limit: Typ. 2.0A
- Short Protection Option: Latched off mode, when short condition > 4ms
- Fold-Back, keeps operating at a lower operating frequency
- Standby Current: Typ. 0μA
- Operating Frequency: 330kHz, 500kHz, 1000kHz, 2400kHz
- Operating Mode: PWM
- Efficiency: (Vin=12V, Vout=5.0V / 1A) Max. 90%
- Additional Circuits: Thermal Protection, Under Voltage Lock Out
- Soft Start Function: Typ. 1.0ms
- Package R1245K: (L2.0 x W2.0 x H0.6mm) DFN(PLP)2020-8
- Package R1245N: (L2.9 x W2.8 x H1.1mm) SOT23-6W
- Package R1245S: (L5.2 x W6.2 x H1.5mm) HSOP-8E
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Ricoh Europe (Netherlands) B.V. is Ricoh Company Ltd.'s regional headquarters. Located in Amstelveen, The Netherlands, it is responsible for marketing, sales and service of Ricoh's products in Europe, the Middle East and Africa. In Europe, Ricoh has three manufacturing sites: two at Ricoh UK Products Ltd. Telford, UK; GR Advanced Materials Ltd., Stirling, UK; and Ricoh Industries France S.A., Colmar, France. In addition, Ricoh Europe's European network comprises 14 sales subsidiaries and affiliates. In the fiscal year ending March 31, 2006, revenues from Ricoh's European operations totalled over € 3 billion, accounting for 22.7% of the company's global revenues. Ricoh's worldwide sales increased with 5.6% totalling over € 13.6 billion. In March 2001 Ricoh established the European Semiconductor Support Centre to support distributors and customers with their applications or other enquiries about Power Management and Real Time Clock ICs.
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