SLVS413F – OCTOBER 2002 – REVISED DECEMBER 2010
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SOFT START
All inductive step-up converters exhibit high inrush current during start-up if no special precaution is made. This
can cause voltage drops at the input rail during start up and may result in an unwanted or early system shut
down.
I
LIM
The TPS61040/41 limits this inrush current by increasing the current limit in two steps starting from
4
for 256
I
LIM
cycles to
2
for the next 256 cycles, and then full current limit (see
ENABLE
Pulling the enable (EN) to ground shuts down the device reducing the shutdown current to 1
mA
(typical).
Because there is a conductive path from the input to the output through the inductor and Schottky diode, the
output voltage is equal to the input voltage during shutdown. The enable pin needs to be terminated and should
not be left floating. Using a small external transistor disconnects the input from the output during shutdown as
shown in
UNDERVOLTAGE LOCKOUT
An undervoltage lockout prevents misoperation of the device at input voltages below typical 1.5 V. When the
input voltage is below the undervoltage threshold, the main switch is turned off.
THERMAL SHUTDOWN
An internal thermal shutdown is implemented and turns off the internal MOSFETs when the typical junction
temperature of 168°C is exceeded. The thermal shutdown has a hysteresis of typically 25°C. This data is based
on statistical means and is not tested during the regular mass production of the IC.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature (unless otherwise noted)
Supply voltages on pin V
IN
Voltages on pins EN, FB
Switch voltage on pin SW
T
J
T
stg
(1)
(2)
(2)
(1)
UNIT
–0.3 V to 7 V
–0.3 V to V
IN
+ 0.3 V
30 V
See Dissipation Rating Table
–40°C to 150°C
–65°C to 150°C
(2)
(2)
Continuous power dissipation
Operating junction temperature
Storage temperature
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to network ground terminal.
DISSIPATION RATING TABLE
PACKAGE
DBV
DDC, DRV
R
qJA
250°C/W
76°C/W
T
A
≤
25°C
POWER RATING
357 mW
1300 mW
DERATING
FACTOR
ABOVE
T
A
= 25°C
3.5 mW/°C
13 mW/°C
T
A
= 70°C
POWER RATING
192 mW
688 mW
T
A
= 85°C
POWER RATING
140 mW
500 mW
4
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