Datasheet

Hiccup Mode off-time
Soft-Start
Restart delay
1V
2V
4V
Count to Eight
1V
T
HICCUP
=
5 µA
C
RES
x (2.0Vx8)
10 µA
C
RES
x ((2.0Vx8) + 1.0V)
+
T
CS
=
C
RES
x 1.0V
30 PA
LM5046
www.ti.com SNVS703G –FEBRUARY 2011–REVISED MARCH 2013
HICCUP MODE CURRENT LIMIT RESTART
The operation of the hiccup mode restart circuit is explained in the FUNCTIONAL DESCRIPTION section. During
a continuous current limit condition, the RES pin is charged with 30µA current source. The restart delay time
required to reach the 1.0V threshold is given by:
(10)
This establishes the number of current limit events allowed before the IC initiates a hiccup restart sequence. For
example, if the C
RES
=0.01µF, the time TCS as noted in Figure 33 is 334µs. Once the RES pin reaches 1.0V, the
30µA current source is turned-off and a 10µA current source is turned-on during the ramp up to 4V and a 5µA is
turned on during the ramp down to 2V. The hiccup mode off-time is given by:
(11)
With a C
RES
=0.01µF, the hiccup time is 49ms. Once the hiccup time is finished, the RES pin is pulled-low and the
SS pin is released allowing a soft-start sequence to commence. Once the SS pin reaches 1V, the PWM pulses
will commence. The hiccup mode provides a cool-down period for the power converter in the event of a
sustained overload condition thereby lowering the average input current and temperature of the power
components during such an event.
Figure 33. Hiccup Mode Delay and Soft-Start Timing Diagram
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