LP2960IMX-33 Datasheet, PDF (13/24 Pages) Texas Instruments – LP2960 Adjustable Micropower 0.5A Low-Dropout Regulators

LP2960
www.ti.com
SNVS112C – APRIL 1999 – REVISED APRIL 2013
The comparator has an open-collector output which requires an external pull-up resistor. This resistor may be
connected to the LP2960 output or another supply voltage.
Best operation is obtained by connecting the pull-up to the LP2960 output. If the pull-up resistor is connected to
an external 5V supply, the error flag will incorrectly signal “HIGH” whenever V_IN < 1.3V (see Figure 26).
In selecting a value for the pull-up resistor, note that while the output can sink 400 μA, this current adds to
battery drain. Suggested values range from 100 kΩ–1 MΩ. The resistor is not required if the output is unused.
If a large output capacitance is used, a false logic “HIGH” can be generated when V_IN ≈1.3V. In this case, the
error output becomes a high impedance, causing the voltage at the error output to rise to its pull-up value. If the
pull-up resistor is connected to V_OUT, the error output can rise to 1.2V (which is a logic “HIGH” signal incorrectly
signifying the output is in regulation).
The user may wish to divide down the error flag voltage using equal-value resistors (10 kΩ suggested) to ensure
a low-level logic signal during any fault condition, while still allowing a valid high logic level during normal
operation.
AUXILIARY COMPARATOR
The LP2960 contains an auxiliary comparator whose inverting input is connected to the 1.23V reference. The
auxiIiary comparator has an open-collector output whose electrical characteristics are similar to the dropout
detection comparator. The non-inverting input and output are brought out for external connections.
SHUTDOWN INPUT
A logic-level signal will shut off the regulator output when a “LOW” (< 1.2V) is applied to the Shutdown input.
To prevent possible mis-operation, the Shutdown input must be actively terminated. If the input is driven from
open-collector logic, a pull-up resistor (20 kΩ–100 kΩ recommended) should be connected from the Shutdown
input to the regulator input.
If the Shutdown input is driven from a source which actively pulls low and high (like an op-amp), the puIl-up
resistor is not required, but may be used.
If the Shutdown input is to be unused, the cost of the pull-up resistor can be saved by tying the Shutdown input
directly to the regulator input.
IMPORTANT: Since the Absolute Maximum Ratings state that the Shutdown input can not go more than 0.3V
below ground, the reverse-battery protection feature which protects the regulator input is sacrificed if the
Shutdown input is tied directly to the regulator input.
If reverse-battery protection is required in an application, the pull-up resistor between the Shutdown input and the
regulator input must be used.
GROUND CONNECTIONS
The pins designated GND (see Connection Diagram) must be connected to the high-current ground point in the
circuit.
The GND pins are electrically connected (through the lead frame) to the die substrate, making them ideal for
conducting ground current or heat (see HEATSINKING).
The surface-mount (D) package also has an Analog Ground pin, which is the ground point on the die for the
regulator reference circuitry.
Along with the Sense pin, the availability of the Analog Ground pin allows the designer the ability to use “remote”
sensing and eliminate output voltage errors due to IR drops occurring along PC board traces.
IMPORTANT: The Analog Ground pin must be connected to circuit ground at some point for the regulator to
operate.
If remote sensing is not needed, the Analog Ground pin can simply be pin-strapped to the adjacent GND pin.
Copyright © 1999–2013, Texas Instruments Incorporated
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