Datasheet
LM3481
SNVS346E –NOVEMBER 2007–REVISED APRIL 2012
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
V
IN
=12V, R
FA
=40 kΩ unless otherwise indicated under the Conditions column. Typicals and limits appearing in plain type
apply for T
J
= 25°C. Limits appearing in boldfacetype apply over the full Operating Temperature Range (-40°C to 125°C).
Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
(1) (2)
Symbol Parameter Conditions Min Typ Max Units
R
DS1 (ON)
Driver Switch On Resistance (top) I
DR
= 0.2A, V
IN
= 5V 4 Ω
R
DS2 (ON)
Driver Switch On Resistance (bottom) I
DR
= 0.2A 2 Ω
V
IN
< 6V V
IN
V
DR (max)
Maximum Drive Voltage Swing
(3)
V
V
IN
≥ 6V 6
D
max
Maximum Duty Cycle 85 %
t
min
(on) Minimum On Time 250 ns
I
SUPPLY
Supply Current (switching) See
(4)
3.7 5.0 mA
V
FA/SYNC/SD
= 3V
(5)
, V
IN
= 12V 9 15
I
Q
Quiescent Current in Shutdown Mode µA
V
FA/SYNC/SD
= 3V
(5)
, V
IN
= 5V 5 10
V
SENSE
Current Sense Threshold Voltage 100 160 190 mV
V
SC
Over Load Current Limit Sense Voltage 157 220 275 mV
V
SL
Internal Compensation Ramp Voltage 90 mV
Output Over-voltage Protection (with
V
OVP
V
COMP
= 1.4V 26 85 135 mV
respect to feedback voltage)
(6)
Output Over-Voltage Protection
V
OVP(HYS)
V
COMP
= 1.4V 28 70 106 mV
Hysteresis
Gm Error Amplifier Transconductance V
COMP
= 1.4V 216 450 690 µmho
V
COMP
= 1.4V
A
VOL
Error Amplifier Voltage Gain 35 60 66 V/V
I
EAO
= 100 µA (Source/Sink)
Source, V
COMP
= 1.4V, V
FB
= 1.1V 475 640 837 µA
Error Amplifier Output Current (Source/
I
EAO
Sink)
Sink, V
COMP
= 1.4V, V
FB
= 1.4V 31 65 100 µA
Upper Limit, V
FB
= 0V, COMP Pin
2.45 2.70 2.93 V
Floating
V
EAO
Error Amplifier Output Voltage Swing
Lower Limit, V
FB
= 1.4V 0.32 0.60 0.90 V
t
SS
Internal Soft-Start Delay V
FB
= 1.2V, COMP Pin Floating 15 ms
t
r
Drive Pin Rise Time Cgs = 3000 pf, V
DR
= 0V to 3V 25 ns
t
f
Drive Pin Fall Time Cgs = 3000 pf, V
DR
= 3V to 0V 25 ns
Output = High (Shutdown) 1.31 1.40 V
Shutdown signal threshold
(7)
V
SD
FA/SYNC/SD pin
Output = Low (Enable) 0.40 0.68 V
V
SD
= 5V −1
I
SD
Shutdown Pin Current FA/SYNC/SD pin µA
V
SD
= 0V 20
T
SD
Thermal Shutdown 165 °C
T
sh
Thermal Shutdown Hysteresis 10 °C
θ
JA
Thermal Resistance DGS Package 200 °C/W
(3) The drive pin voltage, V
DR
, is equal to the input voltage when input voltage is less than 6V. V
DR
is equal to 6V when the input voltage is
greater than or equal to 6V.
(4) For this test, the FA/SYNC/SD Pin is pulled to ground using a 40 kΩ resistor .
(5) For this test, the FA/SYNC/SD Pin is pulled to 3V using a 40 kΩ resistor.
(6) The over-voltage protection is specified with respect to the feedback voltage. This is because the over-voltage protection tracks the
feedback voltage. The over-voltage threshold can be calculated by adding the feedback voltage (V
FB
) to the over-voltage protection
specification.
(7) The FA/SYNC/SD pin should be pulled to V
IN
through a resistor to turn the regulator off. The voltage on the FA/SYNC/SD pin must be
above the max limit for the Output = High longer than 30 µs to keep the regulator off and must be below the minimum limit for Output =
Low to keep the regulator on.
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