Datasheet

R
1
=
UVLO
on
- UVLO
off
23 PA
UVLO
LM5035
V
PWR
STANDBY
OFFOFF
STANDBY
1.25V
0.4V
23 PA
R2
R1
OVP
off
= 1.25V x
R
1
+ R
2
+ R
3
R
3
¨
¨
©
§
¨
¨
©
§
UVLO
off
= 1.25V x
R
1
+ R
2
+ R
3
R
2
+ R
3
¨
¨
©
§
¨
¨
©
§
LM5035
SNVS428G –JANUARY 2006–REVISED MARCH 2013 www.ti.com
Table 1. UVO/OVP Divider Formulas
Outputs disabled due to VIN falling below UVLO threshold
(11)
Outputs enabled due to VIN rising above UVLO threshold UVLO
on
= UVLO
off
+ (23µA x R
1
)
Outputs disabled due to VIN rising above OVP threshold
(12)
Outputs enabled due to VIN falling below OVP threshold OVP
on
= OVP
off
- [23µA x (R1 + R2)]
The typical operating ranges of undervoltage and overvoltage thresholds are calculated from the above
equations. For example, for resistor values R1 = 86.6kΩ, R2 = 2.10kΩ and R3 = 1.40kΩ the computed
thresholds are:
UVLO turn-off = 32.2V
UVLO turn-on = 34.2V
OVP turn-on = 78.4V
OVP turn-off = 80.5V
Figure 23. Remote Standby and Disable Control
To maintain the threshold’s accuracy, a resistor tolerance of 1% or better is recommended.
The design process starts with the choice of the voltage difference between the UVLO enabling and disabling
thresholds. This will also approximately set the difference between OVP enabling and disabling regulation:
(13)
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