Electrical Characteristics (Continued)
Limits in standard typeface are for T
J
=
25˚C, and limits in boldface type apply over the full operating temperature range. Un-
less otherwise specified: V
IN
=
6V, I
L
=
1 mA, C
L
=
2.2 µF, V
SD
=
3V.
Symbol Parameter Conditions Typical
LP2957AI LP2957I
Units
Min Max Min Max
e
n
Output Noise Voltage C
L
=
2.2 µF 500
µV
RMS
(10 Hz to 100 kHz)
I
L
=
100 mA
C
L
=
33 µF 320
SHUTDOWN INPUT
VSD(ON) Output Turn-On 1.155 1.305 1.155 1.305 V
Threshold Voltage 1.140 1.320 1.140 1.320
HYST Hysteresis 6 mV
I
B
Input Bias V
IN(SD)
=
0V to 5V 10 −30 30 −30 30 nA
Current −50 50 −50 50
DROPOUT DETECTION COMPARATOR
I
OH
Output “HIGH” V
OH
=
30V 0.01 1 1 µA
Leakage 22
V
OL
Output “LOW” V
IN
=
4V 150 250 250 mV
Voltage I
O
(COMP)=400 µA 400 400
V
THR
Upper Threshold (Note 8) −240 −320 −150 −320 −150 mV
(Max) Voltage −380 −100 −380 −100
V
THR
Lower Threshold (Note 8) −350 −450 −230 −450 −230 mV
(Min) Voltage −640 −160 −640 −160
HYST Hysteresis (Note 8) 60 mV
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
J
(MAX), the junction-to-ambient thermal resistance, θJA,
and the ambient temperature, T
A
. 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 and 73˚C/W for the TO-263. 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
JA
is 50˚C/W, with 1 square inch of copper
area, θ
JA
is 37˚C/W; and with 1.6 or more square inches of copper area, θJAis 32˚C/W. The junction-to-case thermal resistance 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 LP2957 (see Application Hints).
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 voltage differential at which the output voltage drops 100 mV below the value measured with a 1V input
to output 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 ef-
fects. Specifications are for a 200 mA load pulse at V
IN
=
20V (3W pulse) for T=10 ms.
Note 8: Voltages are referenced to the nominal regulated output voltage.
Note 9: 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.
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