Datasheet
TPS54478
www.ti.com
SLVSAS2 –JUNE 2011
THERMAL INFORMATION
TPS54478
THERMAL METRIC
(1)(2)(3)
(RTE) UNITS
(QFN-16) PINS
θ
JA
Junction-to-ambient thermal resistance 49.1
ψ
JT
Junction-to-top characterization parameter 0.7
ψ
JB
Junction-to-board characterization parameter 21.8
°C/W
θ
JC(top)
Junction-to-case(top) thermal resistance 50.7
θ
JC(bottom)
Junction-to-case(bottom) thermal resistance 7.5
θ
JB
Junction-to-board thermal resistance 21.8
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
(2) Maximum power dissipation may be limited by overcurrent protection
(3) Power rating at a specific ambient temperature TA should be determined with a junction temperature of 150°C. This is the point where
distortion starts to substantially increase. Thermal management of the PCB should strive to keep the junction temperature at or below
150°C for best performance and long-term reliability. See power dissipation estimate in application section of this data sheet for more
information.
ELECTRICAL CHARACTERISTICS
T
J
= –40°C to 150°C, VIN = 2.95 to 6 V (unless otherwise noted)
DESCRIPTION CONDITIONS MIN TYP MAX UNIT
SUPPLY VOLTAGE (VIN PIN)
Operating input voltage 2.95 6.0 V
Input under voltage lockout threshold No voltage hysteresis 2.6 V
Shutdown supply current EN = 0 V, 25°C, 2.95 V ≤ VIN ≤ 6 V 0.7 2.5 μA
Quiescent Current - I
q
VSENSE = 0.7 V, VIN = 5 V, 25°C, RT = 78.7 kΩ 525 700 μA
ENABLE AND UVLO (EN PIN)
Rising 1.30
Enable threshold V
Falling 1.21
Enable threshold + 50 mV –3.4
Input current μA
Enable threshold – 50 mV –0.64
VOLTAGE REFERENCE (VSENSE PIN)
Voltage Reference 2.95 V ≤ VIN ≤ 6 V, –40°C <T
J
< 150°C 0.594 0.600 0.606 V
MOSFET
BOOT-PH = 5 V 30 60
High side switch resistance mΩ
BOOT-PH = 3.3 V 37 70
VIN = 5 V 30 60
Low side switch resistance mΩ
VIN = 3.3 V 37 70
ERROR AMPLIFIER
Input current 7 nA
Error amplifier transconductance (gm) –2 μA < I
(COMP)
< 2 μA, V
(COMP
) = 1 V 225 μmhos
Error amplifier transconductance (gm) during –2 μA < I
(COMP)
< 2 μA, V
(COMP)
= 1 V,
77 μmhos
slow start Vsense = 0.4 V
Error amplifier source/sink V
(COMP)
= 1 V, 100 mV overdrive ±20 μA
COMP to Iswitch gm 14 A/V
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