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LT3009 Series

3009fd

PIN FUNCTIONS

SHDN (Pin 1/Pin 5): Shutdown. Pulling the SHDN pin

low puts the LT3009 into a low power state and turns the

output off. If unused, tie the SHDN pin to VIN. The LT3009

does not function if the SHDN pin is not connected. The

SHDN pin cannot be driven below GND unless tied to the

IN pin. If the SHDN pin is driven below GND while IN is

powered, the output will turn on. SHDN pin logic cannot

be referenced to a negative rail.

GND (Pins 2, 3, 4/Pin 6): Ground. Connect the bottom

of the resistor divider that sets output voltage directly to

GND for the best regulation.

IN (Pin 5/Pin 4): Input. The IN pin supplies power to the

device. The LT3009 requires a bypass capacitor at IN if

the device is more than six inches away from the main

input ﬁlter capacitor. In general, the output impedance

of a battery rises with frequency, so it is advisable to

include a bypass capacitor in battery-powered circuits. A

bypass capacitor in the range of 0.1μF to 10μF will suf-

ﬁce. The LT3009 withstands reverse voltages on the IN

pin with respect to ground and the OUT pin. In the case

of a reversed input, which occurs with a battery plugged

in backwards, the LT3009 acts as if a large resistor is in

series with its input. Limited reverse current ﬂows into

the LT3009 and no reverse voltage appears at the load.

The device protects both itself and the load.

OUT (Pin 6/Pins 2, 3): Output. This pin supplies power to

the load. Use a minimum output capacitor of 1μF to prevent

oscillations. Large load transient applications require larger

output capacitors to limit peak voltage transients. See the

Applications Information section for more information on

output capacitance and reverse output characteristics.

ADJ (Pin 7/Pin 1): Adjust. This pin is the error ampliﬁer’s

inverting terminal. Its 300pA typical input bias current

ﬂows out of the pin (see curve of ADJ Pin Bias Current vs

Temperature in the Typical Performance Characteristics

section). The ADJ pin voltage is 600mV referenced to GND

and the output voltage range is 600mV to 19.5V. This pin

is not connected in the ﬁxed output voltage versions.

NC (Pins 7, 8/Pin 1): No Connect. For the adjustable voltage

version, Pin 8 is an NC pin in the SC70 package. For the

ﬁxed voltage versions, Pin 7 and Pin 8 are NC pins in the

SC70 package, and Pin 1 is an NC pin in the DFN package.

NC pins are not tied to any internal circuitry. They may be

ﬂoated, tied to VIN or tied to GND.

Exposed Pad (Pin 7, DFN Package Only): Ground. The

Exposed Pad (backside) of the DFN package is an electri-

cal connection to GND. To ensure optimum performance,

solder Pin 7 to the PCB and tie directly to Pin 6.

(SC70/DFN)

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