LP3963, LP3966

SNVS067H – APRIL 2000 – REVISED APRIL 2013

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SENSE PIN

In applications where the regulator output is not very close to the load, LP3966 can provide better remote load

regulation using the SENSE pin. Figure 22 depicts the advantage of the SENSE option. LP3963 regulates the

voltage at the output pin. Hence, the voltage at the remote load will be the regulator output voltage minus the

drop across the trace resistance. For example, in the case of a 3.3V output, if the trace resistance is 100m

Ω, the

sense pin. Connecting the sense pin to the remote load will provide regulation at the remote load, as shown in

Figure 22. Improving remote load regulation using LP3966

SHUTDOWN OPERATION

A CMOS Logic level signal at the shutdown (SD) pin will turn-off the regulator. Pin SD must be actively

terminated through a 10k

Ω pull-up resistor for a proper operation. If this pin is driven from a source that actively

pulls high and low (such as a CMOS rail to rail comparator), the pull-up resistor is not required. This pin must be

tied to Vin if not used.

DROPOUT VOLTAGE

The dropout voltage of a regulator is defined as the minimum input-to-output differential required to stay within

2% of the nominal output voltage. The LP3963/LP3966 use an internal MOSFET with an Rds(on) of 240m

Ω

(typically). For CMOS LDOs, the dropout voltage is the product of the load current and the Rds(on) of the internal

MOSFET.

REVERSE CURRENT PATH

The internal MOSFET in LP3963 and LP3966 has an inherent parasitic diode. During normal operation, the input

voltage is higher than the output voltage and the parasitic diode is reverse biased. However, if the output is

pulled above the input in an application, then current flows from the output to the input as the parasitic diode gets

forward biased. The output can be pulled above the input as long as the current in the parasitic diode is limited to

200mA continuous and 1A peak.

POWER DISSIPATION/HEATSINKING

LP3963 and LP3966 can deliver a continuous current of 3A over the full operating temperature range. A heatsink

may be required depending on the maximum power dissipation and maximum ambient temperature of the

application. Under all possible conditions, the junction temperature must be within the range specified under

operating conditions. The total power dissipation of the device is given by:

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