LT3050EDDB LINER [Linear Technology], LT3050EDDB Datasheet - Page 10

• Manufacturer Part Number: LT3050EDDB
• Description: 100mA, Low Noise Linear Regulator With Precision Current Limit And Diagnostic Functions
• Manufacturer: LINER [Linear Technology]

PIN FUNCTIONS
LT3050
REF/BYP (Pin 1): Bypass/Soft-Start. Connecting a single
capacitor from this pin to GND bypasses the LT3050’s
reference noise and soft-starts the reference. A 10nF
bypass capacitor typically reduces output voltage noise to
30μV
is directly proportional to the REF/BYP capacitor value.
If the LT3050 is placed in shutdown, REF/BYP is actively
pulled low by an internal device to reset soft-start. If low
noise or soft-start performance is not required, this pin
must be left fl oating (unconnected). Do not drive this pin
with any active circuitry. Because the REF/BYP pin is the
reference input to the error amplifi er, stray capacitance at
this point should be minimized. Special attention should
be given to any stray capacitances that can couple external
signals onto the REF/BYP pin producing undesirable output
transients or ripple. A minimum REF/BYP capacitance of
100pF is recommended.
I
Pin. This pin is the collector of a PNP current mirror that
outputs 1/200th of the power PNP load current. This pin
is also the input to the minimum output current fault
comparator. Connecting a resistor between I
sets the minimum output current fault threshold. For
detailed information on how to set the I
value, please see the Operation section.
A small external decoupling capacitor (10nF minimum)
is required to improve I
current programming is not required, the I
be left fl oating (unconnected).
FAULT (Pin 3): Fault Pin. This is an open collector logic
pin which asserts during current limit, thermal limit or
a minimum current fault condition. The maximum low
logic output level is defi ned for sinking 100μA of current.
Off state logic may be as high as 45V without damaging
internal circuitry regardless of the V
SHDN (Pin 4): Shutdown. Pulling the SHDN pin low puts the
LT3050 into a low power state and turns the output off. Drive
the SHDN pin with either logic or an open collector/drain
with a pull-up resistor. The resistor supplies the pull-up
current to the open collector/drain logic, normally several
10
MIN
RMS
(Pin 2): Minimum Output Current Programming
in a 10Hz to 100kHz bandwidth. Soft-start time
MIN
PSRR. If minimum output
IN
used.
MIN
MIN
MIN
pin resistor
pin must
and GND
microamperes, and the SHDN pin current, typically less than
2μA. If unused, connect the SHDN pin to IN. The LT3050
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 may turn on. SHDN pin logic cannot
be referenced to a negative rail.
IN (Pin 5,6): Input. These pins supply power to the
device. The LT3050 requires a local IN bypass capacitor
if it is located more than six inches from the main input
fi lter capacitor. In general, battery output impedance rises
with frequency, so adding a bypass capacitor in battery
powered circuits is advisable. A minimum input of 1μF
generally suffi ces.
OUT (Pin 7,8): Output. These pins supply power to the
load. Stability requirements demand a minimum 2.2μF
ceramic output capacitor to prevent oscillations. Large
load transient applications require larger output capacitors
to limit peak voltage transients. See the Applications
Information section for details on transient response and
reverse output characteristics. Permissible output voltage
range is 600mV to 44.5V.
ADJ (Pin 9): Adjust. This pin is the error amplifi er’s inverting
terminal. Its typical bias of 16nA current fl ows out of the
pin (see curve of ADJ Pin Bias Current vs. Temperature
in the Typical Performance Characteristics section). The
typical ADJ pin voltage is 600mV referenced to GND.
GND (PIN 10, Exposed Pad Pin 13): Ground. The exposed
pad of the DFN and MSOP packages is an electrical
connection to GND. To ensure proper electrical and
thermal performance, solder Pin 13 to the PCB ground
and tie directly to Pin 10. Connect the bottom of the output
voltage setting resistor divider directly to GND (Pin 10)
for optimum load regulation performance.
I
Pin. This pin is the collector of a current mirror PNP that
is 1/200
also the input to the current limit amplifi er. Current limit
threshold is set by connecting a resistor between the I
pin and GND.
MAX
(Pin 11): Precision Current Limit Programming
th
the size of the output power PNP. This pin is
MAX
3050f