LP2960

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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 VIN < 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 k

Ω–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 VIN ≈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 VOUT, 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 k

Ω 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 k

Ω–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.

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Product Folder Links: LP2960