I
LIM
4
I
LIM
2
TPS61040
TPS61041
SLVS413F – OCTOBER 2002 – REVISED DECEMBER 2010
www.ti.com
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.
The TPS61040/41 limits this inrush current by increasing the current limit in two steps starting from
for 256
cycles to
for the next 256 cycles, and then full current limit (see
Figure 14
).
ENABLE
Pulling the enable (EN) to ground shuts down the device reducing the shutdown current to 1
m
A (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
Figure 18
.
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)
(1)
UNIT
Supply voltages on pin V
IN
(2)
–0.3 V to 7 V
Voltages on pins EN, FB
(2)
–0.3 V to V
IN
+ 0.3 V
Switch voltage on pin SW
(2)
30 V
Continuous power dissipation
See Dissipation Rating Table
T
J
Operating junction temperature
–40°C to 150°C
T
stg
Storage temperature
–65°C to 150°C
(1)
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.
(2)
All voltage values are with respect to network ground terminal.
DISSIPATION RATING TABLE
DERATING
T
A
≤
25°C
FACTOR
T
A
= 70°C
T
A
= 85°C
PACKAGE
R
q
JA
POWER RATING
ABOVE
POWER RATING
POWER RATING
T
A
= 25°C
DBV
250°C/W
357 mW
3.5 mW/°C
192 mW
140 mW
DDC, DRV
76°C/W
1300 mW
13 mW/°C
688 mW
500 mW
4
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