LT3041 datasheet(30/36 Pages) AD

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Data Sheet

LT3041

APPLICATIONS INFORMATION

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Rev. 0 | 30 of 36

or if the EN/UV pin is pulled high after the input voltage is already

turned on. The load-line in such cases intersects the output-current

profile at two points. The regulator now has two stable operating

points. With this double intersection, the input-power supply may

need to be cycled down to zero and brought back up again to

result in the output recover. Other LDO regulators with foldback

current-limit protection (such as the LT1965 and LT1963A) also

exhibit this phenomenon; therefore, it is not unique to the LT3041.

PROTECTION FEATURES

The LT3041 incorporates several protection features for battery-

powered applications. Precision current-limit and thermal-overload

protection protect the LT3041 against overload and fault conditions

at the output of the device. For normal operation, do not allow the

junction temperature to exceed 125°C.

To protect the low-noise error amplifier of the LT3041, the SET-to-

OUTS protection clamp limits the maximum voltage between SET

and OUTS with a maximum DC current of 20 mA through the

clamp. Therefore, for applications where SET is actively driven by

a voltage source, the voltage source must be current limited to 20

mA or less. Moreover, to limit the transient current flowing through

these clamps during a transient fault condition, limit the maximum

value of the SET pin capacitor (CSET) to 22 μF.

The LT3041 also incorporates reverse-input protection whereby the

IN pin withstands reverse voltages of up to –20 V without causing

any input-current flow and without developing negative voltages at

the OUT pin. The regulator protects both itself and the load against

batteries that are plugged in backwards.

In circuits where a backup battery is required, several different input

and output conditions can occur. The output voltage can be held up

while the input is either pulled to GND, pulled to some intermediate

voltage, or left open-circuit. In all cases, the reverse-current protec-

tion circuitry prevents current flow from the output to the input.

Nonetheless, due to the OUTS-to-SET clamp, unless the SET pin

is floating, current can flow to GND through the SET pin resistor as

well as up to 15 mA to GND through the output overshoot recovery

circuitry. This current flow through the output overshoot recovery

circuitry can be significantly reduced by placing a Schottky diode

between the OUTS and SET pins, with its anode at the OUTS pin.

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