Datasheet

LM3445
SNVS570L –JANUARY 2009–REVISED MAY 2013 www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Limits 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). Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at T
J
= +25ºC, and are provided for reference purposes only.
Symbol Parameter Conditions Min Typ Max Units
INTERNAL PWM RAMP
f
RAMP
Frequency 5.85 kHz
V
RAMP
Valley voltage 0.96 1.00 1.04 V
Peak voltage 2.85 3.00 3.08
D
RAMP
Maximum duty cycle 96.5 98.0 %
DIM DECODER
t
ANG_DET
Angle detect rising threshold Observed on BLDR pin 6.79 7.21 7.81 V
V
ASNS
ASNS filter delay 4 µs
ASNS VMAX 3.85 4.00 4.15 V
I
ASNS
ASNS drive capability sink V
ASNS
= 2V 7.6 mA
ASNS drive capability source V
ASNS
= 2V -4.3
DIM low sink current V
DIM
= 1V 1.65 2.80
DIM High source current V
DIM
= 4V -4.00 -3.00
V
DIM
DIM low voltage PWM input voltage 0.9 1.33 V
threshold
DIM high voltage 2.33 3.15
V
TSTH
Tri-state threshold voltage Apply to FLTR1 pin 4.87 5.25 V
R
DIM
DIM comparator tri-state impedance 10 MΩ
CURRENT SENSE COMPARATOR
V
FLTR2
FLTR2 open circuit voltage 720 750 780 mV
R
FLTR2
FLTR2 impedance 420 kΩ
V
OS
Current sense comparator offset voltage -4.0 0.1 4.0 mV
GATE DRIVE OUTPUT
V
DRVH
GATE high saturation I
GATE
= 50 mA 0.24 0.50 V
V
DRVL
GATE low saturation I
GATE
= 100 mA 0.22 0.50
I
DRV
Peak souce current GATE = V
CC
/2 -0.77 A
Peak sink current GATE = V
CC
/2 0.88
t
DV
Rise time C
load
= 1 nF 15 ns
Fall time C
load
= 1 nF 15
THERMAL SHUTDOWN
T
SD
Thermal shutdown temperature See
(1)
165 °C
Thermal shutdown hysteresis 20
THERMAL SHUTDOWN
R
θJA
VSSOP-10 junction to ambient 121 °C/W
(1) Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power
dissipation exists, special care must be paid to thermal dissipation issues in board design. In applications where high power dissipation
and/or poor package thermal resistance is present, 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), the maximum power dissipation
of the device in the application (P
D-MAX
), and the junction-to ambient thermal resistance of the part/package in the application (R
θJA
), as
given by the following equation: T
A-MAX
= T
J-MAX-OP
– (R
θJA
× P
D-MAX
).
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