LT1763 Series
PIN FUNCTIONS (DE12/S8)
NC (Pins 1, 4, 9, 12) DE12 Only: No Connect. No connect
BYP (Pin 6/Pin 4): Bypass. The BYP pin is used to bypass
thereferenceoftheLT1763regulatorstoachievelownoise
performance from the regulator. The BYP pin is clamped
pins have no connection to any internal circuitry. These
pins may be tied to either GND or V , or left floating.
IN
internally to 0.6V (one V ). A small capacitor from the
BE
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
tolimitpeakvoltagetransients. SeetheApplicationsInfor-
mationsectionformoreinformationonoutputcapacitance
and reverse output characteristics.
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
20μV
over a 10Hz to 100kHz bandwidth. If not used,
RMS
this pin must be left unconnected.
GND (Pins 7, Exposed Pad Pin 13/Pins 3, 6, 7): Ground.
The exposed pad of the DFN package is an electrical con-
nection to GND. To ensure proper electrical and thermal
performance, solder Pin 13 to the PCB ground and tie
directly to Pin 7. Connect the bottom of the output volt-
age setting resistor divider directly to the GND pins for
optimum load regulation performance.
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).TheADJpinvoltageis1.22Vreferencedtoground
and the output voltage range is 1.22V to 20V.
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
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 regula-
tion 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 re-
pin must be connected to V . The device will be in the low
IN
sistance (R ) of PC traces between the regulator and the
P
power shutdown state if the SHDN pin is not connected.
load. These may be eliminated by connecting the SENSE
pin to the output at the load as shown in Figure 1 (Kelvin
Sense Connection).
IN(Pin10,11/Pin8):Input.Powerissuppliedtothedevice
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 imped-
ance 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.
R
P
8
1
IN
OUT
LT1763
+
5
2
+
SHDN SENSE
LOAD
V
IN
GND
3
R
P
1763 F01
Figure 1. Kelvin Sense Connection
Note that the voltage drop across the external PC traces will
add to the dropout voltage of the regulator. The SENSE pin
biascurrentis10μAatthenominalratedoutputvoltage.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.
1763fg
14
Linear [ Linear ]
