Datasheet

LM3940
www.ti.com SNVS114E –MAY 1999–REVISED MARCH 2013
ELECTRICAL CHARACTERISTICS
Limits in standard typeface are for T
J
= 25°C, and limits in boldface type apply over the full operating temperature range.
Unless otherwise specified: V
IN
= 5V, I
L
= 1A, C
OUT
= 33 μF.
Symbol Parameter Conditions Typical LM3940
(1)
Units
min max
3.20 3.40
V
O
Output Voltage 5 mA ≤ I
L
≤ 1A 3.3 V
3.13 3.47
I
L
= 5 mA
Line Regulation 20 40
4.5V ≤ V
IN
≤ 5.5V
(1)
mV
50
Load Regulation 50 mA ≤ I
L
≤ 1A 35
80
(2)
I
L
(DC) = 100 mA
Z
O
Output Impedance I
L
(AC) = 20 mA (rms) 35 mΩ
f = 120 Hz
4.5V ≤ V
IN
≤ 5.5V 15
10
I
L
= 5 mA 20
I
Q
Quiescent Current mA
V
IN
= 5V 200
110
I
L
= 1A 250
BW = 10 Hz–100 kHz
e
n
Output Noise Voltage 150 μV (rms)
I
L
= 5 mA
0.8
I
L
= 1A 0.5 V
1.0
Dropout Voltage
V
DO
(2)
150
I
L
= 100 mA 110 mV
200
I
L
(SC) Short Circuit Current R
L
= 0 1.7 1.2 A
(1) All limits specified for T
J
= 25°C are 100% tested and are used to calculate Outgoing Quality Levels. All limits at temperature extremes
are verified via correlation using standard Statistical Quality Control (SQC) methods.
(2) Dropout voltage is defined as the input-output differential voltage where the regulator output drops to a value that is 100 mV below the
value that is measured at V
IN
= 5V.
THERMAL PERFORMANCE
3-Lead TO-220 4 °C/W
Thermal Resistance, Junction-to-Case, θ
JC
3-Lead DDPAK/TO-263 4 °C/W
8-Lead WSON 6 °C/W
3-Lead TO-220 60 °C/W
Thermal Resistance, Junction-to-Ambient, θ
JA
3-Lead DDPAK/TO-263 80 °C/W
8-Lead WSON
(1)
35 °C/W
(1) The maximum allowable power dissipation is a function of the maximum junction temperature, T
J
, the junction-to-ambient thermal
resistance, θ
JA
, and the ambient temperature, T
A
. Exceeding the maximum allowable power dissipation will cause excessive die
temperature, and the regulator will go into thermal shutdown. The value of θ
JA
(for devices in still air with no heatsink) is 60°C/W for the
TO-220 package, 80°C/W for the DDPAK/TO-263 package, and 174°C/W for the SOT-223 package. The effective value of θ
JA
can be
reduced by using a heatsink (see APPLICATION HINTS for specific information on heatsinking). The value of θ
JA
for the WSON
package is specifically dependant on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal
resistance and power dissipation for the WSON package, refer to Application Note AN-1187 SNOA401. The θ
JA
rating for the WSON is
with a JESD51-7 test board having 6 thermal vias under the exposed pad.
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