Datasheet

LM3478
LM3478-Q1
www.ti.com SNVS085V –JULY 2000–REVISED FEBRUARY 2013
Electrical Characteristics
Specifications in Standard type face are for T
J
= 25°C, and in bold type face apply over the full Operating Temperature
Range. Unless otherwise specified, V
IN
= 12V, R
FA
= 40kΩ
Symbol Parameter Conditions Typical Limit Unit
V
FB
Feedback Voltage V
COMP
= 1.4V, 1.26 V
2.97 ≤ V
IN
≤ 40V 1.2416/1.228 V(min)
1.2843/1.292 V(max)
ΔV
LINE
Feedback Voltage Line 2.97 ≤ V
IN
≤ 40V 0.001 %/V
Regulation
ΔV
LOAD
Output Voltage Load I
EAO
Source/Sink ±0.5 %/A (max)
Regulation
V
UVLO
Input Undervoltage Lock-out 2.85 V
2.97 V(max)
V
UV(HYS)
Input Undervoltage Lock-out 170 mV
Hysteresis 130 mV (min)
210 mV (max)
F
nom
Nominal Switching Frequency R
FA
= 40KΩ 400 kHz
350 kHz(min)
440 kHz(max)
R
DS1 (ON)
Driver Switch On Resistance I
DR
= 0.2A, V
IN
= 5V 16 Ω
(top)
R
DS2 (ON)
Driver Switch On Resistance I
DR
= 0.2A 4.5 Ω
(bottom)
V
DR (max)
Maximum Drive Voltage V
IN
< 7.2V V
IN
V
Swing
(1)
V
IN
≥ 7.2V 7.2
D
max
Maximum Duty Cycle
(2)
100 %
T
min
(on) Minimum On Time 325 nsec
210 nsec(min)
600 nsec(max)
I
SUPPLY
Supply Current (non-switching)
(3)
2.7 mA
3.3 mA (max)
I
Q
Quiescent Current in V
FA/SD
= 5V
(4)
, 5 µA
Shutdown Mode V
IN
= 5V 10 µA (max)
V
SENSE
Current Sense Threshold V
IN
= 5V 156 mV
Voltage 135/ 125 mV (min)
180/ 190 mV (max)
V
SC
Short-Circuit Current Limit V
IN
= 5V 343 250 mV
Sense Voltage 415 mV (min)
mV (max)
V
SL
Internal Compensation Ramp V
IN
= 5V 92 mV
Voltage 52 mV(min)
132 mV(max)
V
SL
ratio V
SL
/V
SENSE
0.49 0.30 (min)
0.70 (max)
V
OVP
Output Over-voltage Protection V
COMP
= 1.4V 50 mV
(with respect to feedback 32/ 25 mV(min)
voltage)
(5)
VSSOP Package 78/ 85 mV(max)
SOIC Package 78/100 mV(max)
V
OVP(HYS)
Output Over-Voltage V
COMP
= 1.4V 60 mV
Protection Hysteresis
(5)
20 mV(min)
110 mV(max)
(1) The voltage on the drive pin, V
DR
is equal to the input voltage when input voltage is less than 7.2V. V
DR
is equal to 7.2V when the input
voltage is greater than or equal to 7.2V.
(2) The limits for the maximum duty cycle can not be specified since the part does not permit less than 100% maximum duty cycle
operation.
(3) For this test, the FA/SD pin is pulled to ground using a 40K resistor.
(4) For this test, the FA/SD pin is pulled to 5V using a 40K resistor.
(5) The over-voltage protection is specified with respect to the feedback voltage. This is because the over-voltage protection tracks the
feedback voltage. The overvoltage protection threshold is given by adding the feedback voltage, V
FB
to the over-voltage protection
specification.
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