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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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SS6845GGTR датащи(PDF) 8 Page - Silicon Standard Corp. |
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SS6845GGTR датащи(HTML) 8 Page - Silicon Standard Corp. |
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8 / 13 page  www.SiliconStandard.com 8 of 13 SS6845G 7/21/2005 Rev.3.01 APPLICATION INFORMATION Introduction Short Circuit/Thermal Protection The SS6 845G is a micropower charge pump DC/DC converter that produces a regulated 5V output with an input voltage range from 2.7V to 5.0V. It utilizes the charge pump topology to boost VIN to a regulated output voltage. Regulation is obtained by sensing the output voltage through an internal resistor divider. A switched doubling circuit enables the charge pump when the feedback voltage is lower than the trip point of the internal comparator, and vice versa. When the charge pump is enabled, a two-phase non-overlapping clock activates the charge pump switches. To maximize battery life for a battery-use application, quiescent current is limited to no more than 13 µA. The SS6 845G includes built-in short circuit current limiting as well as over-temperature protection. During a short circuit condition, the output current is automatically constrained to approximately 170mA. This short circuit current will cause a rise in the internal IC junction temperature. When the die temperature exceeds 150°C, the thermal protection will shut down the charge pump switching operation and the die temperature will then reduce. Once the die temperature drops below 135 °C, the charge pump switching circuit will restart. If the fault has not been eliminated, the this protection mechanism will repeat again and again, allowing the SS6845G to work continuously in a short circuit condition without damaging the device. Operation This kind of converter uses capacitors to store and transfer energy. Since the capacitors can’t change their voltage level abruptly, the voltage ratio of VOUT over VIN is limited to some range. Capacitive voltage conversion is obtained by switching a capacitor periodically. It first charges the capacitor by connecting it across a voltage source and then connects it to the output. Referring to Fig. 19, during the on state of internal clock, Q1 and Q4 are closed, which charges C1 to VIN level. During the off state, Q3 and Q2 are closed. The output voltage is VIN plus VC1, that is, 2VIN. Shutdown In shutdown mode, the output is disconnected from the input. The input current is extremely low since most of the circuitry is turned off. Due to high impedance, the shutdown pin cannot float. Efficiency The diagrams, Fig. 20 and Fig. 21 show the operation of the charge pump in the on and off states. R DS-ON is the resistance of the switching element during conduction. ESR is the equivalent series resistance of the flying capacitor C1. ION-AVE and IOFF-AVE are the average current during the on-state and off-state, respectively. D is the duty-cycle, which means the ratio of the on-state time to the total cycle time. Let's look at capacitor C1 - assuming that capacitor C 1, has reached its steady state, then the amount of charge flowing into C 1 during the on-state is equal to that flowing out of C1 during the off-state. C1 Q1 Q3 Q2 Q4 VOUT VIN COUT CIN Fig. 19 The circuit of charge pump |
Аналогичный номер детали - SS6845GGTR |
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Аналогичное описание - SS6845GGTR |
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