Datasheet LT1580, LT1580-2.5 (Analog Devices) - 6

LT1580/LT1580-2.5
W BLOCK DIAGRA
VCONTROL VPOWER + – SENSE VOUT FOR FIXED VOLTAGE DEVICE 1580 BD ADJ GND
U U W U APPLICATIONS INFORMATION
The LT1580 is a low dropout regulator designed to power reducing the dropout voltage by a VBE compared to the new generation of microprocessors. Low dropout conventional designs. The current requirement for the regulators have become more common in desktop com- control voltage is relatively small, equal to approximately puter systems as microprocessor manufacturers have 1% of the output current or about 70mA for a 7A load. The moved away from 5V only CPUs. A wide range of supply bulk of this current is drive current for the NPN output requirements exists today with new voltages just over the transistor. This drive current becomes part of the output horizon. In many cases the input-output differential is very current. small, effectively disqualifying many of the low dropout The control voltage must be at least 1V greater than the regulators on the market today. The LT1580 is designed to output voltage to obtain optimum performance. The maxi- make use of multiple power supplies, present in most mum voltage on the VCONTROL pin is 13V. The maximum systems, to reduce the dropout voltage. This two supply voltage at the VPOWER pin is limited to 7V. GDN pin current approach maximizes efficiency. for fixed voltage devices is 6mA (typ) and is constant as a The second supply, at least 1V greater than the output function of load. ADJ pin current for adjustable devices is voltage, is used to provide power for the control circuitry 60µA at 25°C and varies proportional to absolute tempera- and supply the drive current to the NPN output transistor. ture. This allows the NPN to be driven into saturation, thereby 6