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EUP7559 Datasheet(PDF) 9 Page - Eutech Microelectronics Inc |
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EUP7559 Datasheet(HTML) 9 Page - Eutech Microelectronics Inc |
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9 / 10 page  EUP7559 DS7559 Ver 1.0 May. 2007 9 Application Note The EUP7559 is a high performance, low quiescent current power management IC consisting of two µCap low dropout regulators. The first regulator is capable of sourcing 300mA at output voltages from 1.5V to 3.3V. The second regulator is capable of sourcing 300mA of current at output voltages from 1.5V to 3.3V. These outputs are stable with 2.2uF output capacitor at any load. Enable A and B The enable inputs allow for logic control of both output voltages with individual enable inputs. The EUP7559 is turned off by pulling the VEN pin low, and turned on by pulling it high. If this feature is not used, the VEN pin should be tied to VIN to keep the regulator output on at all time. To assure proper operation, the signal source used to drive the VEN input must be able to swing above and below the specified turn-on/off voltage thresholds listed in the Electrical Characteristics section under VIL and VIH. External Capacitors Like any low-dropout regulator, the EUP7559 requires external capacitors for regulator stability. The EUP7559 is specifically designed for portable applications requiring minimum board space and smallest components. These capacitors must be correctly selected for good performance. Input Capacitor An input capacitance of ≈2.2µF or greater is required between the EUP7559 input pin and ground (the amount of the capacitance may be increased without limit). This capacitor must be located a distance of not more than 1cm from the input pin and returned to a clean analog ground. Any good quality ceramic, tantalum, or film capacitor may be used at the input. Output Capacitor The EUP7559 is designed specifically to work with very small ceramic output capacitors. A ceramic capacitor (temperature characteristics X7R, X5R, Z5U, or Y5V) in 2.2µF to 22µF range with 5mΩ to 500mΩ ESR range is suitable in the EUP7559 application circuit. The output capacitor must meet the requirement for minimum amount of capacitance and also have an ESR (Equivalent Series Resistance) value which is within a stable range (5mΩ to 500mΩ) No-Load Stability The EUP7559 will remain stable and in regulation with no external load. This is specially important in CMOS RAM keep-alive applications. Capacitor Characteristics The EUP7559 is designed to work with ceramic capacitors on the output ceramic capacitors are the smallest, least expensive and have the lowest ESR values (which makes them best for eliminating high frequency noise). The ESR of a typical 2.2µF ceramic capacitor is in the range of 10mΩ to 40mΩ, which easily meets the ESR requirement for stability by the EUP7559. The ceramic capacitor’s capacitance can vary with temperature. The capacitor type X7R, which operates over a temperature range of -55°C to +125°C, will only vary the capacitance to within ±15%. Most large value ceramic capacitors ( ≈ 2.2µF) are manufactured with Z5U or Y5V temperature characteristics. Their capacitance can drop by more than 50% as the temperature goes from 25°C to 85°C. Therefore, X7R is recommended over Z5U and Y5V in applications where the ambient temperature will change significantly above or below 25°C. Noise Bypass Capacitor Connecting a 0.01µF capacitor between the BP pin and ground significantly reduces noise on the regulator output. This cap is connected directly to a high impedance node in the bandgap reference circuit. Any significant loading on this node will cause a change on the regulated output voltage. For this reason, DC leakage current through this pin must be kept as low as possible for best output voltage accuracy. The types of capacitors best suited for the noise bypass capacitor are ceramic and film. Unlike many other LDO’s, addition of a noise reduction capacitor does not effect the load transient response of the device. |
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