Datasheet

RES
SS1
and
SS2
OUT1
0V
2.55V
5.0V
t1 t2 t3
Current Limit Detected at
CS1 and/or CS2
OUT2
5
0
PA
1
PA
#1.5V
DC1
0.5V
Clk1, Clk2
0.5V
5.0V
2.55V
Restart
Comparator
Q
S
R
Drivers Off
Restart
Latch
DC2
SS1
SS2
To Output
Drivers
PWM #1
PWM #2
COMP2
COMP1
CS2
CS1
Current
Sense Circuit
RES
Soft-start #1
Soft-start #2
Voltage
Feedback
Voltage
Feedback
LM5034
SS2
SS1
49 PA
Restart
Current
Source
Logic
Drivers Off
SS1
200 mV
SS
Logic
SS2
200 mV
SS
Logic
Current
Limit
Current
Sense Circuit
20PA
C
SS1
C
SS2
Current
Limit
49PA1PA
1PA
C
RES
10 PA
LM5034
SNVS347A –FEBRUARY 2005–REVISED APRIL 2013 www.ti.com
Figure 22. Current Limit Restart Circuit
Figure 23. Current Limit Restart Timing
Soft-Start
Each soft-start circuit allows the corresponding regulator to gradually reach a steady state operating point,
thereby reducing startup current surges and output overshoot. Upon turn-on, both SS pins are internally held at
ground. When VCC increases past its under-voltage threshold (UVT), the SS pins are released and internal 50
µA current sources charge the external capacitors. The voltage at each COMP pin follows the SS pin, and when
COMP reaches ≊1.5V, the output pulses commence at a low duty cycle. The voltage at the SS pins continues to
increase and saturates at ≊5.0V, The voltage at each COMP pin increases to the value required for regulation
where it is controlled by its voltage feedback loop (see Figure 5).
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