LT3085 Просмотр технического описания (PDF) - Linear Technology

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LT3085

3µA IQ, 20mA, 45V Low Dropout Fault Tolerant Linear Regulators

Linear Technology 

LT3007 Series

PIN FUNCTIONS

SHDN (Pin 1): Shutdown. Pulling the SHDN pin low puts

the LT3007 into a low power state and turns the output off.

If unused, tie the SHDN pin to VIN. The LT3007 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): Ground. Connect the bottom of the

resistor divider that sets output voltage directly to GND

for the best regulation.

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

The LT3007 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 suffice. The LT3007

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

LT3007 acts as if a blocking diode is in series with its

input. No reverse current flows into the LT3007 and no

reverse voltage appears at the load. The device protects

both itself and the load.

NC (Pin 6): No Connect. Pin 6 is an NC pin in the TSOT-23

package. This pin is not tied to any internal circuitry. LTC

recommends that the NC pin be floated for fault tolerant

operation.

OUT (Pin 7): Output. This pin supplies power to the load.

Use a minimum output capacitor of 2.2µF to prevent os-

cillations. 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 8): Adjust. This pin is the error amplifier’s inverting

terminal. Its 400pA 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 44.5V.

SENSE (Pin 8): Sense. For fixed voltage versions of the

LT3007 (LT3007-1.2, LT3007-1.5, LT3007-1.8, LT3007-2.5,

LT3007-3.3, LT3007-5), the SENSE pin is the input to the

error amplifier. Optimum regulation is obtained at the point

where the SENSE pin is connected to the OUT pin of the

regulator. In critical applications, small voltage drops are

caused by the resistance (RP) of PC traces between the

regulator and the load. These may be eliminated by con-

necting the SENSE pin to the output at the load as shown

in Figure 1 (Kelvin Sense Connection). Note that the volt-

age drop across the external PC traces add to the dropout

voltage of the regulator. The SENSE pin bias current is

1µA at the nominal rated output voltage. The SENSE pin

can be pulled below ground (as in a dual supply system

where the regulator load is returned to a negative supply)

and still allow the device to start and operate.

+

VIN

IN

OUT

LT3007

SHDN SENSE

GND

RP

+

RP

LOAD

3007 F01

Figure 1. Kelvin Sense Connection

3007f

For more information www.linear.com/LT3007

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