Datasheet

t3 =
C
SS
x 4V
55 PA
= 73 k: x C
SS
t2 =
C
SS
x 1V
1 PA
= 1 M: x C
SS
t1 =
C
RES
x 2.5V
22 PA
= 114 k: x C
RES
RES
SS
LO
HO
5V
t1
Current Limit Detected
at CS
2.5V
0V
+55 PA
+1 PA
t2 t3
#1V
OVP
LM5035
STANDBY
NTC
THERMISTOR
T
R2
R1
1.25V
5V
23 PA
V
REF
LM5035
SNVS428G –JANUARY 2006–REVISED MARCH 2013 www.ti.com
R2 provides temperature hysteresis by raising the OVP comparator input by R2 x 23µA. For example, if a 22kΩ
resistor is selected for R2, then the OVP pin voltage will increase by 22kΩ x 23µA = 506mV. The NTC
temperature must therefore fall by 506mV / 25mV per°C = 20°C before the LM5035 switches from the standby
mode to the normal mode.
Figure 25. Remote Thermal Protection
HICCUP MODE CURRENT LIMIT RESTART (RES)
The basic operation of the hiccup mode current limit restart is described in the functional description. The delay
time to restart is programmed with the selection of the RES pin capacitor C
RES
as illustrated in Figure 25.
Figure 26. Hiccup Over-Load Restart Timing
In the case of continuous cycle-by-cycle current limit detection at the CS pin, the time required for C
RES
to reach
the 2.5V hiccup mode threshold is:
(17)
For example, if C
RES
= 0.01µF the time t1 is approximately 1.14 ms.
The cool down time, t2 is set by the soft-start capacitor (C
SS
) and the internal 1µA SS current source, and is
equal to:
(18)
If C
SS
= 0.01 µF t2 is ≊10 ms.
The soft-start time t3 is set by the internal 55µA current source, and is equal to:
(19)
If C
SS
= 0.01 µF t3 is ≊730µs.
24 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM5035