LP2966 datasheet(13/15 Pages) NSC

13 / 15 page

Applications Information (Continued)

The internal error flag comparators have open drain output

stages. Hence, the ERROR pins should be pulled high

through a pull up resistor. Although the ERROR pin can sink

current of 1mA, this current adds to the battery drain. Hence,

the value of the pull up resistor should be in the range of

100k

Ω to 1MΩ. The ERROR pins must be connected to

ground if this function is not used. It should also be noted

that when the shutdown pins are pulled low, the ERROR pins

are forced to be invalid for reasons of saving power in shut-

down mode.

Shutdown Operation

The two LDO regulators in the LP2966 have independent

shutdown. A CMOS Logic level signal at the shutdown( SD)

pin will turn-off the corresponding regulator. Pins SD1 and

SD2 must be actively terminated through a 100k

Ω pull-up re-

sistor for a proper operation. If these pins are 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. These

pins must be tied to Vin if not used.

Drop-Out Voltage

The drop-out voltage of a regulator is defined as the mini-

mum input-to-output differential required to stay within

100mV of the output voltage measured with a 1V differential.

The LP2966 uses an internal MOSFET with an Rds(on) of

Ω. For CMOS LDOs, the drop-out voltage is the product of

the load current and the Rds(on) of the internal MOSFET.

Reverse Current Path

The internal MOSFET in the LP2966 has an inherent para-

sitic diode. During normal operation, the input voltage is

higher than the output voltage and the parasitic diode is re-

verse biased. However, if the output is pulled above the input

in an application, then current flows from the output to the in-

put 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 150mA.

Maximum Output Current Capability

Each output in the LP2966 can deliver a current of more than

150mA over the full operating temperature range. However,

the maximum output current capability should be derated by

the junction temperature. Under all possible conditions, the

junction temperature must be within the range specified un-

der operating conditions. The LP2966 is available in

MSOP-8 package. This package has a junction to ambient

temperature coefficient (

ja)

of 235 ˚C/W with minimum

amount of copper area. The total power dissipation of the de-

vice is approximately given by:

D =(Vin -VOUT1)IOUT1 +(Vin-VOUT2)IOUT2

The maximum power dissipation, P

Dmax, that the device can

tolerate can be calculated by using the formula

Dmax =(Tjmax -TA)/θja

where T

jmax is the maximum specified junction temperature

(125˚C), and T

A is the ambient temperature.

The following figures show the variation of thermal coeffi-

cient with different layout scenarios.

DS100850-35

FIGURE 3. Error Flag Operation

LP2966 Scheda tecnica(PDF) 13 Page - National Semiconductor (TI)

LP2966 Scheda tecnica(HTML) 13 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Scheda tecnica Scarica

Link URL