176325 datasheet(13/20 Pages) LINER

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LT1763 Series

1763fe

PIN FUNCTIONS

NC (Pins 1, 4, 9, 12) DE12 Only: No Connect. No connect

pins have no connection to any internal circuitry. These

pins may be tied to either GND or VIN, or left ﬂoating.

OUT (Pins 2, 3/Pin 1): Output. The output supplies power

to the load. A minimum output capacitor of 3.3μF is re-

quired to prevent oscillations. Larger output capacitors

will be required for applications with large transient loads

to limit peak voltage transients. See the Applications Infor-

mation section for more information on output capacitance

and reverse output characteristics.

ADJ (Pin 5/Pin 2): Adjust. For the adjustable LT1763, this

is the input to the error ampliﬁer. This pin is internally

clamped to ±7V. It has a bias current of 30nA which ﬂows

into the pin (see the curve of ADJ Pin Bias Current vs

Temperature in the Typical Performance Characteristics

section). The ADJ pin voltage is 1.22V referenced to ground

and the output voltage range is 1.22V to 20V.

SENSE (Pin 5/Pin 2): Output Sense. For ﬁxed volt-

age versions of the LT1763 (LT1763-1.5/LT1763-1.8/

LT1763-2.5/LT1763-3/LT1763-3.3/LT1763-5), the SENSE

pin is the input to the error ampliﬁer. Optimum regulation

will be 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 connecting the SENSE

pin to the output at the load as shown in Figure 1 (Kelvin

Sense Connection).

supply system where the regulator load is returned to a

negative supply) and still allow the device to start and

operate.

BYP (Pin 6/Pin 4): Bypass. The BYP pin is used to bypass

the reference of the LT1763 regulators to achieve low noise

performance from the regulator. The BYP pin is clamped

internally to ±0.6V (one VBE). A small capacitor from the

output to this pin will bypass the reference to lower the

output voltage noise. A maximum value of 0.01μF can

be used for reducing output voltage noise to a typical

20μVRMS over a 10Hz to 100kHz bandwidth. If not used,

this pin must be left unconnected.

GND (Pins 7/Pins 3, 6, 7): Ground.

SHDN (Pin 8/Pin 5): Shutdown. The SHDN pin is used

to put the LT1763 regulators into a low power shutdown

state. The output will be off when the SHDN pin is pulled

low. The SHDN pin can be driven either by 5V logic or

open-collector logic with a pull-up resistor. The pull-up

resistor is required to supply the pull-up current of the

open-collector gate, normally several microamperes, and

the SHDN pin current, typically 1μA. If unused, the SHDN

pin must be connected to VIN. The device will be in the low

power shutdown state if the SHDN pin is not connected.

IN (Pin 10, 11/Pin 8): Input. Power is supplied to the device

through the IN pin. A bypass capacitor is required on this

pin 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 1μF to 10μF is sufﬁcient.

The LT1763 regulators are designed to withstand reverse

voltages on the IN pin with respect to ground and the OUT

pin. In the case of a reverse input, which can happen if

a battery is plugged in backwards, the device will act as

if there is a diode in series with its input. There will be

no reverse current ﬂow into the regulator and no reverse

voltage will appear at the load. The device will protect both

itself and the load.

Exposed Pad (Pin 13) DE12 Only: Ground. The Exposed

Pad must be soldered to the PCB ground for rated thermal

performance.

(DE12/S8)

Note that the voltage drop across the external PC traces will

add to the dropout voltage of the regulator. The SENSE pin

bias current is 10μA at the nominal rated output voltage.

The SENSE pin can be pulled below ground (as in a dual

SHDN

1763 F01

OUT

VIN

SENSE

GND

LT1763

LOAD

Figure 1. Kelvin Sense Connection

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