Datasheet

LT1964
10
1964fb
PIN FUNCTIONS
ADJ (Adjustable Devices only): For the Adjustable LT1964,
this is the Input to the Error Amplifi er. The ADJ pin has a
bias current of 30nA that fl ows out of the pin. The ADJ pin
voltage is –1.22V referenced to ground, and the output
voltage range is –1.22V to –20V. A parasitic diode exists
between the ADJ pin and the input of the LT1964. The ADJ
pin cannot be pulled more negative than the input during
normal operation, or more than 0.5V more negative than
the input during a fault condition.
BYP: The BYP Pin is used to Bypass the Reference of
the LT1964 to Achieve Low Noise Performance from the
Regulator. 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 30μV
RMS
over a 10Hz
to 100kHz bandwidth. If not used, this pin must be left
unconnected.
Exposed Pad (DFN Package Only): IN. Connect to IN
(Pins 7, 8) at the PCB.
GND: Ground.
IN: Power is Supplied to the Device Through the Input Pin.
A bypass capacitor is required on this pin if the device
is more than six inches away from the main input fi lter
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 suffi cient.
OUT: The Output Supplies Power to the Load. A minimum
output capacitor of 1μF is required to prevent oscillations.
Larger output capacitors will be required for applications
with large transient loads to limit peak voltage transients.
A parasitic diode exists between the output and the input.
The output cannot be pulled more negative than the input
during normal operation, or more than 0.5V below the input
during a fault condition. See the Applications Information
section for more information on output capacitance and
reverse output characteristics.
SHDN: The SHDN Pin is used to put the LT1964 into a Low
Power Shutdown State. The SHDN pin is referenced to
the GND pin for regulator control, allowing the LT1964 to
be driven by either positive or negative logic. The output
of the LT1964 will be off when the SHDN pin is pulled
within ±0.8V of GND. Pulling the SHDN pin more than
–1.9V or +1.6V will turn the LT1964 on. The SHDN pin
can be driven 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, typi-
cally 3μA out of the pin (for negative logic) or 6μA into
the pin (for positive logic). If unused, the SHDN pin must
be connected to V
IN
. The device will be shut down if the
SHDN pin is open circuit. For the LT1964-BYP, the SHDN
pin is internally connected to V
IN
. A parasitic diode exists
between the SHDN pin and the input of the LT1964. The
SHDN pin cannot be pulled more negative than the input
during normal operation, or more than 0.5V below the
input during a fault condition.
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