LP2954ISX/NOPB National Semiconductor, LP2954ISX/NOPB Datasheet - Page 5
Manufacturer Part Number
IC REG LDO MICROPOWER TO-263
Specifications of LP2954ISX/NOPB
Voltage - Output
Voltage - Input
6 ~ 30 V
Voltage - Dropout (typical)
0.47V @ 250mA
Number Of Regulators
Current - Output
-40°C ~ 125°C
Package / Case
TO-263-3, D²Pak (3 leads + Tab), TO-263AA
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Limit (min)
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the
device outside of its rated operating conditions.
Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, T
and the ambient temperature, T
. The maximum allowable power dissipation at any ambient temperature is calculated using:
Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. The junction-to-
ambient thermal resistance of the TO-220 (without heatsink) is 60˚C/W, 73˚C/W for the TO-263, and 160˚C/W for the SO-8. If the TO-263 package is used, the
thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package: Using 0.5 square inches of copper area, θ
50˚C/W; with 1 square inch of copper area, θ
is 37˚C/W; and with 1.6 or more square inches of copper area, θ
is 3˚C/W. If an external heatsink is used, the effective junction-to-ambient thermal resistance is the sum of the junction-to-case resistance (3˚C/W), the specified
thermal resistance of the heatsink selected, and the thermal resistance of the interface between the heatsink and the LP2954. Some typical values are listed for
interface materials used with TO-220:
TABLE 1. Typical Values of Case-to-Heatsink
Thermal Resistance (˚C/W) (Data from AAVID Eng.)
Mica with grease
Note 3: Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 4: Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested separately for load regulation in the load
ranges 0.1 mA–1 mA and 1 mA–250 mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential.
Note 6: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground pin current.
Note 7: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation
effects. Specifications are for 200 mA load pulse at V
Note 8: When used in dual-supply systems where the regulator load is returned to a negative supply, the output voltage must be diode-clamped to ground.
Note 9: Connect a 0.1µF capacitor from the output to the feedback pin.
Note 10: V
Note 11: Two seperate tests are performed, one covering V
Note 12: V
Note 13: Comparator thresholds are expressed in terms of a voltage differential at the Feedback terminal below the nominal reference voltage measured at
(NOM)+1V. To express these thresholds in terms of output voltage change, multiply by the Error amplifier gain, which is V
Note 14: Human body model, 200pF discharged through 1.5kΩ.
Typical Performance Characteristics
TABLE 2. Typical Values of Case-to-Heatsink
Thermal Resistance (˚C/W) (Data from Thermalloy)
Thermalfilm (0.002) with grease
= 20V (3W pulse) for T = 10 ms.
=2.5V to V
(NOM)+1V and the other test for V
(MAX), the junction-to-ambient thermal resistance, θ
is 32˚C/W. The junction-to-case thermal resistance
=2.5V to V
(NOM)+1V to 30V.