Datasheet LT1764A (Analog Devices) - 10

LT1764A Series
U U U PI FU CTIO S DD/TO-220/TSSOP SHDN (Pin 1/1/10):
Shutdown. The SHDN pin is used to Applications Information section for more information on put the LT1764A regulators into a low power shutdown output capacitance and reverse output characteristics. state. The output will be off when the SHDN pin is pulled
SENSE (Pin 5/Pin 5/Pin 6):
Sense. For fixed voltage low. The SHDN pin can be driven either by 5V logic or versions of the LT1764A (LT1764A-1.5/LT1764A-1.8/ open-collector logic with a pull-up resistor. The pull-up LT1764A-2.5/LT1764A-3.3), the SENSE pin is the input resistor is required to supply the pull-up current of the to the error amplifier. Optimum regulation will be ob- open-collector gate, normally several microamperes, and tained at the point where the SENSE pin is connected to the the SHDN pin current, typically 7µA. If unused, the SHDN OUT pin of the regulator. In critical applications, small pin must be connected to VIN. The device will be in voltage drops are caused by the resistance (R the low power shutdown state if the SHDN pin is not P) of PC traces between the regulator and the load. These may be connected. eliminated by connecting the SENSE pin to the output at
IN (Pin 2/Pin 2/Pins 12, 13, 14):
Input. Power is supplied the load as shown in Figure 1 (Kelvin Sense Connection). to the device through the IN pin. A bypass capacitor is Note that the voltage drop across the external PC traces required on this pin if the device is more than six inches will add to the dropout voltage of the regulator. The SENSE away from the main input filter capacitor. In general, the pin bias current is 600µA at the nominal rated output output impedance of a battery rises with frequency, so it voltage. The SENSE pin can be pulled below ground (as in is advisable to include a bypass capacitor in battery- a dual supply system where the regulator load is returned powered circuits. A bypass capacitor in the range of 1µF to to a negative supply) and still allow the device to start 10µF is sufficient. The LT1764A regulators are designed to and operate. withstand reverse voltages on the IN pin with respect to
ADJ (Pin 5/Pin 5/Pin 6):
Adjust. For the adjustable LT1764A, ground and the OUT pin. In the case of a reverse input, this is the input to the error amplifier. This pin is internally which can happen if a battery is plugged in backwards, the clamped to ±7V. It has a bias current of 3µA which flows device will act as if there is a diode in series with its input. into the pin. The ADJ pin voltage is 1.21V referenced to There will be no reverse current flow into the regulator and ground and the output voltage range is 1.21V to 20V. no reverse voltage will appear at the load. The device will protect both itself and the load. RP 2 4 IN OUT
NC (Pins 2, 11, 15) TSSOP Only:
No Connect. LT1764A
GND (Pin 3/Pin 3/Pins 1, 7, 8, 9, 16, 17):
Ground. 1 5 + + SHDN V SENSE LOAD IN
OUT (Pin 4/Pin 4/Pins 3, 4, 5):
Output. The output GND 3 supplies power to the load. A minimum output capacitor RP of 10µF is required to prevent oscillations. Larger output 1764 F01 capacitors will be required for applications with large transient loads to limit peak voltage transients. See the
Figure 1. Kelvin Sense Connection
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