LP3992 datasheet(4/9 Pages) NSC

4 / 9 page

Electrical Characteristics (Continued)

Note 3: The package can pass MSL (moisture sensitivity level) 1 at 260˚C.

Additional information on lead temperature can be obtained from National Semiconductor web pages

http://www.national.com/packaging/general.html

http://www.national.com/packaging/plastic.html

Note 4: The Maximum power dissipation of the device is dependant on the maximum allowable junction temperature for the device and the ambient temperature.

This relationship is given by the formula

PD =(TJ -TA)/θJA

Where TJ is the junction temperature, TA is the ambient temperature, and θJA is the junction-to-ambient thermal resistance. The Maximum Power dissipation across

the device related to the operational conditions can be calculated using the formula

PD =(VIN(MAX) -VOUT(MAX))*(IOUT(MAX))

Substituting the device values gives the max power dissipation = (5.2V - 1.5V)(0.03) = 0.111W. This figure for Maximum power dissipation can be used to derive the

maximum ambient temperature. For the SOT23-5 package

θJA = 220˚C/W, thus for this device the maximum temperature difference, (TJ -TA), is 24.4˚C, (0.111 *

220). This gives the maximum ambient temperature for operation as 100.6˚C, (125 - 24.4). Similarly the numbers for the absolute maximum case can be derived

using a figure of 150˚C for the junction temperature.

Note 5: The human body is 100pF discharge through 1.5kW resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin.

Note 6: The device maintains the regulated output voltage without the load.

Note 7: This electrical specification is guaranteed by design.

Note 8: Time for VOUT to rise from 50 to 85% of VOUT(nom). (figure 1)

Note 9: Time from VSD = 1.15V to VOUT = 95%(VOUT(nom)). (figure 1)

Note 10: Time for VOUT to fall from 85 to 50% of VOUT(nom). (figure 1)

Note 11: Time from VSD = 0.4V to VOUT = 5%(VOUT(nom). (figure 1)

Note 12: Short circuit current is measured on the input supply line at the point when the short circuit condition reduces the output voltage to 95% of its nominal value.

Note 13: All limits are guaranteed. All electrical characteristics having room-temperature limits are tested during production at TJ = 25˚C or correlated using

Statistical Quality Control methods. Operation over the temperature specification is guaranteed by correlating the electrical characteristics to process and

temperature variations and applying statistical process control.

Output Capacitor, Recommended Specifications

Symbol

Parameter

Conditions

Typ

Limit

Units

Min

Max

Output Capacitor

Capacitance(Note 14)

1.0

µF

ESR

500

Ω

Note 14: Capacitor types recommended are X7R, Y5V, and Z5U. X7R tolerance is quoted as 15% over temperature.

20041203

FIGURE 1. Figure 1. T

on/Toff Timing Diagram

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