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ST619LB 데이터시트(PDF) 2 Page - STMicroelectronics |
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ST619LB 데이터시트(HTML) 2 Page - STMicroelectronics |
2 / 9 page ST619LB SERIES 2/9 OPERATING PRINCIPLE The ST619LB is able to provide a regulated 5V output from a 2V to 3.6V (two battery cells) input. Internal charge pump and external capacitors generate the 5V output, eliminating the need for inductors. The output voltage is regulated to 5V, ±4% by a pulse skipping controller that turns on the charge pump when the output voltage begins to drop. To maintain the greatest efficiency the internal charge pump of the device operates as a voltage doubler when VI ranges from 3.0V to 3.6V and as a voltage tripler when VI ranges from 2.0V to 2.5V. When VI ranges from 2.5V to 3.0V , the ST619LB switches between doubler and tripler mode on alternating cycles, making a 2.5 x VI charge pump. To further enhance the efficiency over the input range, an internal comparator selects the higher of VI or VO to run the ST619LB’s circuitry. With VI = 2V and IO = 20mA the typical efficiency value is 80%. In tripler mode (see block diagram), when the S1 switches close, the S2 switches open and capacitors C1 and C2 charge up to VI. On the second half of the cycle, C1 and C2 are connected in series between IN and OUT when the S1 switches open and S2 switches close. In the doubler mode only C2 is used. During one oscillator cycle, energy is transferred from the input to the charge pump capacitors, and then from the charge pump capacitors to the output capacitors and load. The number of cycles within a given time frame increases as the load increases or as the input supply voltage decreases. In the limiting case , the charge pumps operate continuously, and the oscillator frequency is nominally 500kHz. Shut Down Mode The ST619LB enters low power shut down mode when SHDN is a logic high. In shut down mode, OUT is disconnected from the IN and VO falls to 0V. The SHDN pin is connected to ground for normal operation. SHDN is a CMOS compatible input. ABSOLUTE MAXIMUM RATINGS Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is not implied. THERMAL DATA (*) This value depends from thermal design of PCB on which the device is mounted. Symbol Parameter² Value Unit VI DC Input Voltage -0.3 to 5.5 V VO Output Voltage -0.3 to 5.5 V VSHDN Shutdown Input Voltage -0.3 to (VI + 0.3) V IO Output Current Continuous 120 mA Tstg Storage Temperature Range -55 to +150 °C Top Operating Junction Temperature Range -40 to +85 °C Symbol Parameter SO-8 DIP-8 Unit Rthj-amb Thermal Resistance Junction-ambient (*) 160 100 °C/W |
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