Datasheet

LM3450
www.ti.com SNVS681D –NOVEMBER 2010–REVISED MAY 2013
ELECTRICAL CHARACTERISTICS
(1)
(continued)
Unless otherwise specified V
CC
= 14V. Specifications in standard type face are for T
J
= 25°C and those with boldface type
apply over the full Operating Temperature Range ( T
J
= −40°C to +125°C). Typical values represent the most likely
parametric norm at T
A
= T
J
= +25°C, and are provided for reference purposes only.
Symbol Parameter Conditions Min
(2)
Typ
(3)
Max
(2)
Units
PWM Comparator Input Bias Current 20 nA
V
LIM
CS Current Limit Threshold 1.40 1.50 1.60 V
CS Delay to Output 100 ns
CS Blanking Sinking Impedance 1 kΩ
t
LEB
Leading Edge Blanking (LEB) Time 140 ns
ANALOG ADJUST INPUT (V
ADJ
)
V
ADJ-LP
V
ADJ
Low Threshold (Low Power Mode) V
ADJ
Falling 56 75
mV
V
ADJ
Low Hysteresis 50
V
ADJ
Pull-up Current Source 1 µA
V
ADJ
Open Voltage V
ADJ
Open 3 V
DYNAMIC HOLD CIRCUIT (HOLD, I
SEN
)
R
DSON-HD
HOLD MosFET On-Resistance ISEN Short to GND 22 30 42 Ω
V
SEN-REF
I
SEN
Reference Voltage 162 200 232 mV
I
SEN
Bias Current 5 µA
PRE-REGULATOR GATE DRIVE OUTPUT (BIAS)
V
BIAS
BIAS High Voltage @ 100µA V
CC
< V
CC-FALL
18.8 21 22.6
V
BIAS Low Voltage @ 100µA V
CC
> V
CC-RISE
13.5 14 14.5
GATE DRIVER OUTPUT (GATE)
V
GATE-H
GATE Voltage High I
GATE
= 20mA 11.5
V
I
GATE
= 200mA 10.5
GATE Pull Down Resistance 2 8 Ω
GATE Peak Current
(4)
±1.5 A
REFERENCE VOLTAGE OUTPUT (V
REF
)
V
REF
Reference Voltage No Load 2.85 3 3.15 V
Current Limit 1.5 2.0 3.0 mA
DIMMING OUTPUT (DIM, FLT1, FLT2)
FLT1 Output Impedance Standby Mode 500
kΩ
Transition mode 1.6
Triangle Waveform Compared to FLT2 High 1.49 V
Low 15 mV
f
DIM
DIM Frequency 180 460 700 Hz
OFF-TIMERS
t
OFF-MAX
Maximum Off-Time (Normal Operation) 340
µs
t
OFF-LP
Off-Time (Low Power Mode) 42
THERMAL SHUTDOWN
Thermal Limit Threshold
(4)
160
°C
Thermal Limit Hysteresis 20
THERMAL RESISTANCE
θ
JA
Junction to Ambient TSSOP-16
(4)(5)
38.0
°C/W
θ
JC
Junction to Case 10.0
(4) These electrical parameters are specified by design, and are not verified by test.
(5) Junction-to-ambient thermal resistance is highly board-layout dependent. In applications where high maximum power dissipation exists,
namely driving a large MOSFET at high switching frequency from a high input voltage, special care must be paid to thermal dissipation
issues during board design. In high-power dissipation applications, the maximum ambient temperature may have to be derated.
Maximum ambient temperature (T
A-MAX
) is dependent on the maximum operating junction temperature (T
J-MAX-OP
= 125°C for Q1, or
150°C for Q0), the maximum power dissipation of the device in the application (P
D-MAX
), and the junction-to ambient thermal resistance
of the package in the application (θ
JA
), as given by the following equation: T
A-MAX
= T
J-MAX-OP
– (θ
JA
× P
D-MAX
).
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