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ISL9014IRKPZ Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL9014IRKPZ Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 11 page 10 FN9245.3 March 11, 2008 delays the VO2 turn-on until the VO1 output reaches its target level. If EN2 is brought high, and EN1 goes high after VO2 starts its output ramp, then the ISL9014 immediately starts to ramp up the VO1 output. If both EN1 and EN2 are brought high at the same time, the VO1 output has priority, and is always powered up first. During operation, whenever the VIN voltage drops below about 1.8V, the ISL9014 immediately disables both LDO outputs. When VIN rises back above 2.1V, the device re-initiates its start-up sequence and LDO operation will resume automatically. Reference Generation The reference generation circuitry includes a trimmed bandgap, a trimmed voltage reference divider, a trimmed current reference generator, and an RC noise filter. The filter includes the external capacitor connected to the CBYP pin. A 0.01µF capacitor connected CBYP implements a 100Hz lowpass filter, and is recommended for most high performance applications. For the lowest noise application, a 0.1 μF or greater CBYP capacitor should be used. This filters the reference noise to below the 10Hz to 1kHz frequency band, which is crucial in many noise-sensitive applications. The bandgap generates a zero temperature coefficient (TC) voltage for the reference divider. The reference divider provides the regulation reference and other voltage references required for current generation and over-temperature detection. The current generator outputs references required for adaptive biasing as well as references for LDO output current limit and thermal shutdown determination. LDO Regulation and Programmable Output Divider The LDO Regulator is implemented with a high-gain operational amplifier driving a PMOS pass transistor. The design of the ISL9014 provides a regulator that has low quiescent current, fast transient response, and overall stability across all operating and load current conditions. LDO stability is guaranteed for a 1µF to 10µF output capacitor that has a tolerance better than 20% and ESR less than 200m Ω. The design is performance-optimized for a 1µF capacitor. Unless limited by the application, use of an output capacitor value above 4.7µF is not recommended as LDO performance improvement is minimal. Soft-start circuitry integrated into each LDO limits the initial ramp-up rate to about 30µs/V to minimize current surge. The ISL9014 provides short-circuit protection by limiting the output current to about 475mA. Each LDO uses an independently trimmed 1V reference. An internal resistor divider drops the LDO output voltage down to 1V. This is compared to the 1V reference for regulation. The resistor division ratio is programmed in the factory. Overheat Detection The bandgap outputs a proportional-to-temperature current that is indicative of the temperature of the silicon. This current is compared with references to determine if the device is in danger of damage due to overheating. When the die temperature reaches about +145°C, one or both of the LDOs momentarily shut down until the die cools sufficiently. In the overheat condition, only the LDO sourcing more than 50mA will be shut off. This does not affect the operation of the other LDO. If both LDOs source more than 50mA and an overheat condition occurs, both LDO outputs are disabled. Once the die temperature falls back below about +110°C, the disabled LDO(s) are re-enabled and soft-start automatically takes place. ISL9014 |
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