Datasheet

EN
LM5002
V
PWR
STANDBY
R2
OFF
OFF
STANDBY
R1
1.26V
0.45V
EN
LM5002
Disable PWM Controller
R1
Disable VCC Regulator
VIN
1.26V
0.45V
6 PA
V
PWR
R2
R2 =
1.26V
I
DIVIDER
+ 6 PA
R1 =
V
PWR
- 1.26V
I
DIVIDER
LM5002
SNVS496D –JANUARY 2007–REVISED MARCH 2013 www.ti.com
(2)
where
• V
PWR
is the desired turn-on voltage
• I
DIVIDER
is an arbitrary current through R1 and R2 (3)
For example, if the LM5002 is to be enabled when V
PWR
reaches 16V, I
DIVIDER
could be chosen as 501 µA which
would set R1 to 29.4 kΩ and R2 to 2.49 kΩ. The voltage at the EN pin should not exceed 10V unless the current
into the 6V protection Zener diode is limited below 4 mA. The EN pin voltage should not exceed 14V at any time.
Be sure to check both the power and voltage rating (some 0603 resistors are rated as low as 50V) for the
selected R1 resistor.
Figure 18. Basic EN (UVLO) Configuration
Remote configuration of the controller’s operational modes can be accomplished with open drain device(s)
connected to the EN pin as shown in Figure 19. A MOSFET or an NPN transistor connected to the EN pin can
force the regulator into the low power ‘off’ state. Adding a PN diode in the drain (or collector) provides the offset
to achieve the standby state. The advantage of standby is that the VCC LDO is not disabled and external
circuitry powered by VCC remains functional.
Figure 19. Remote Standby and Disable Control
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