Datasheet LT3012 (Analog Devices) - 8

LT3012
PIN FUNCTIONS (DFN Package/TSSOP Package) NC (Pins 1, 6, 7, 9, 12)/(Pins 2, 7, 10, 12, 15):
No Con-
SHDN (Pin 8)/(Pin 11):
Shutdown. The SHDN pin is used nect. These pins have no internal connection; connecting to put the LT3012 into a low power shutdown state. The NC pins to a copper area for heat dissipation provides a output will be off when the ⎯SHDN pin is pulled low. The small improvement in thermal performance. SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor. The pull-up resistor is only
OUT (Pins 2, 3)/(Pins 3, 4):
Output.The output supplies required to supply the pull-up current of the open-collec- power to the load. A minimum output capacitor of 3.3μF tor gate, normally several microamperes. If unused, the is required to prevent oscillations. Larger output capaci- SHDN pin must be tied to a logic high or to V tors will be required for applications with large transient IN. loads to limit peak voltage transients. See the Applications
IN (Pins 10, 11)/(Pins 13,14):
Input. Power is supplied Information section for more information on output ca- to the device through the IN pin. A bypass capacitor is pacitance and reverse output characteristics. required on this pin if the device is more than six inches away from the main input fi lter capacitor. In general, the
ADJ (Pin 4)/(Pin 5):
Adjust. This is the input to the error output impedance of a battery rises with frequency, so it is amplifi er. This pin is internally clamped to ±7V. It has a advisable to include a bypass capacitor in battery-powered bias current of 30nA which fl ows into the pin (see curve circuits. A bypass capacitor in the range of 1μF to 10μF is of ADJ Pin Bias Current vs Temperature in the Typical suffi cient. The LT3012 is designed to withstand reverse Performance Characteristics). The ADJ pin voltage is voltages on the IN pin with respect to ground and the OUT 1.24V referenced to ground, and the output voltage range pin. In the case of a reversed input, which can happen if is 1.24V to 60V. a battery is plugged in backwards, the LT3012 will act as
GND (Pins 5, 13)/(Pins 1, 6, 8, 9, 16, 17):
Ground. The if there is a diode in series with its input. There will be no exposed backside of the package is an electrical connection reverse current fl ow into the LT3012 and no reverse volt- for GND. As such, to ensure optimum device operation and age will appear at the load. The device will protect both thermal performance, the exposed pad must be connected itself and the load. directly to pin 5/pin 6 on the PC board.
APPLICATIONS INFORMATION
The LT3012 is a 250mA high voltage low dropout regula-
Adjustable Operation
tor with micropower quiescent current and shutdown. The LT3012 has an output voltage range of 1.24V to 60V. The device is capable of supplying 250mA at a dropout The output voltage is set by the ratio of two external resis- voltage of 400mV. The low operating quiescent current tors as shown in Figure 1. The device servos the output to (40μA) drops to 1μA in shutdown. In addition to the maintain the voltage at the adjust pin at 1.24V referenced low quiescent current, the LT3012 incorporates several to ground. The current in R1 is then equal to 1.24V/R1 protection features which make it ideal for use in bat- and the current in R2 is the current in R1 plus the ADJ tery-powered systems. The device is protected against pin bias current. The ADJ pin bias current, 30nA at 25°C, both reverse input and reverse output voltages. In battery fl ows through R2 into the ADJ pin. The output voltage backup applications where the output can be held up by can be calculated using the formula in Figure 1. The value a backup battery when the input is pulled to ground, the of R1 should be less than 250k to minimize errors in the LT3012 acts like it has a diode in series with its output output voltage caused by the ADJ pin bias current. Note and prevents reverse current fl ow. that in shutdown the output is turned off and the divider current will be zero. 3012fd 8