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CS8140YTHA7 Scheda tecnica(PDF) 6 Page - Cherry Semiconductor Corporation |
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CS8140YTHA7 Scheda tecnica(HTML) 6 Page - Cherry Semiconductor Corporation |
6 / 12 page Precision Voltage Reference The regulated output voltage depends on the precision band gap voltage reference in the IC. By adding an error amplifier into the feedback loop , the output voltage is main- tained within ±4% over temperature and supply variation. Output Stage The composite PNP-NPN output structure (Figure1) pro- vides 500mA (min) of output current while maintaining a low drop out voltage (1.25V) and drawing little quiescent current (7mA). Figure 1: Composite Output Stage of the CS8140/1 The NPN pass device prevents deep saturation of the out- put stage which in turn improves the ICÕs efficiency by preventing excess current from being used and dissipated by the IC. Output Stage Protection The output stage is protected against overvoltage, short circuit and thermal runaway conditions (Figure 2). If the input voltage rises above 30V (e.g. load dump), the output shuts down. This response protects the internal cir- cuitry and enables the IC to survive unexpected voltage transients. Using an emitter sense scheme, the amount of current through the NPN pass transistor is monitored. Feedback circuitry insures that the output current never exceeds a preset limit. Figure 2: Typical Circuit Waveforms for Output Stage Protection. Should the junction temperature of the power device exceed 180ûC (typ), the power transistor is turned off. Thermal shutdown is an effective means to prevent die overheating since the power transistor is the principle heat source in the IC. The CS8140 differs from all other linear regulators in its unique combination of control features. Watchdog and ENABLE Functions VOUT is controlled by the logic functions ENABLE and Watchdog (Table 1). Table 1: VOUT as a Function of ENABLE and Watchdog WDI ENABLE Slow Normal Fast High Low H 55 5 5 5 L 05 0 0 0 VOUT (V) Regulator Control Functions IO VOUT VIN Load Dump Short Circuit Thermal Shutdown > 30V VOUT VIN Voltage Reference and Output Circuitry 6 Dropout Voltage The input-output voltage differential at which the circuit ceases to regulate against further reduction in input volt- age. Measured when the output voltage has dropped 100mV from the nominal value obtained at 14V input, dropout voltage is dependent upon load current and junc- tion temperature. Input Voltage The DC voltage applied to the input terminals with respect to ground. Line Regulation The change in output voltage for a change in the input voltage. The measurement is made under conditions of low dissipation or by using pulse techniques such that the average chip temperature is not significantly affected. Load Regulation The change in output voltage for a change in load current at constant chip temperature. Quiescent Current The part of the positive input current that does not con- tribute to the positive load current. The regulator ground lead current. Ripple Rejection The ratio of the peak-to-peak input ripple voltage to the peak-to-peak output ripple voltage. Current Limit Peak current that can be delivered to the output. Definition of Terms Circuit Description |
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