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ILC7280CS-3025 データシート(PDF) 7 Page - Impala Linear Corporation |
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ILC7280CS-3025 データシート(HTML) 7 Page - Impala Linear Corporation |
7 / 9 page Micropower Dual 150mA CMOS RF LDO™ Regulators with 75dB Ripple Rejection Impala Linear Corporation 7 (408) 574-3939 www.impalalinear.com May 2000 ILC7280 1.8 Advance Output Capacitor An output capacitor is required from VOUTA and VOUTB to GND to prevent oscillation and minimize the effect of load transient currents. The minimum size of the output capac- itor(s) is dependent on the usage of CNOISE and its value. Without CNOISE, a minimum of 1µF is recommended. For CNOISE = 22pF, a minimum of 2.2µF is recommended (See figure 1). Larger values of output capacitance will slow the regulator's response during power up. The upper limit of capacitance is indefinite, however, it should have an equivalent series resistance (ESR) of approximately 5 Ω or less and a series resonance above 1MHz. Stability is assured with the use of a capacitor having ultra-low ESR and as such will not produce low amplitude oscilla- tions nor an underdamped transient response. This allows the use of modern ceramic capacitors in prefer- ence to their more costly Tantalum counterparts. If the system design calls for smaller load currents, lower capacitance may be used. Below 10mA the capacitance may be reduced to 0.47µF and below 1mA to 0.33µF. No-Load Stability The ILC7280 will remain stable and in regulation with no load current. These are desirable performance features for applications such as keep-alive modes in CMOS sys- tems. Split-Supply Operation When using the ILC7280 in a system requiring that the load be returned to the negative voltage source, the out- put(s) must be diode clamped to inhibit significant volt- age excursions below ground. A simple external diode clamp to ground will afford protection from damage to the device. (See figure below). APPLICATIONS INFORMATION +VIN A and B These pins are connected internally through a galvanic connection for maximum power from each regulator, both VINA and VINB must be connected externally to VDD. Enable/Shutdown Forcing ENA and/or ENB to a voltage greater than 2V, enables the regulator(s). These inputs are CMOS logic compatible gates. If this feature is not required, connect ENA and/or ENB to VIN. Note that VINA and VINB are con- nected internally. To minimize the effect of imbalanced current sharing and possible noise, both VINA and VINB should also be connected externally. Input Capacitor A 1µF capacitor should be placed from VINA/B to GND if there is more than 10 inches of wire between the input and the ac filter capacitor or if a battery is used as the input. Reference Bypass Capacitor CNOISE (the reference voltage bypass capacitor) is con- nected to the internal Vref which is common to regulator's A and B. A 22pF capacitor connected between CNOISE and GND decouples the reference output voltage and provides a significant reduction in regulator output noise. An effect of CNOISE also reduces the regulator phase margin. When using CNOISE, output capacitors of 2.2µF or greater are required to maintain stability. Also affected by CNOISE is the start up speed of the ICL7280. The speed is inversely proportional to the value of CNOISE. If a slow or delayed start up time is desired, a larger value of CNOISE is used. Conversely, faster start up times or instant-on applications will require smaller values of CNOISE or its omis- sion with the pin left open. The trade-off of noise to response should be considered. +V IN EN A/ENB -V IN ILC7280 Dual Regulator V OUTA or VOUTB Dext Rload External Diode, Dext inhibits significant voltage excursions below ground in a split power supply load return. |
同様の部品番号 - ILC7280CS-3025 |
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同様の説明 - ILC7280CS-3025 |
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