HV301/HV311
Application Information, cont’d.
However, if the DC/DC PWM Converter with the ENABLE input
circuit configuration was active HIGH, then the apparent choice
of the HV301 would result in the creation of a current path
through the protective diode clamp of the ENABLE input and the
PWRGD output MOSFET of the HV301. For this situation the
HV311 should be used as shown below in Application Circuit 2.
In some applications the PWRGD signal is used to activate load
circuitry on the isolated output side of the DC/DC PWM Con-
verter. In this situation an optocoupler is needed to provide the
required isolation as shown below in Application Circuit 3.
GND
8
V
PWRGD
DD
1
R1
+
487kΩ
ENABLE
+5V
3
2
UV
R2
6.81kΩ
Cload
HV311
OV
DC/DC
PWM
COM
R3
9.76kΩ
CONVERTER
-
V
RAMP
7
SENSE
GATE
6
EE
4
5
C1
10nF
-48V
R4
12.5mΩ
Q1
IRF530
Note: capacitor may be needed to slow PWRGD dv/dt if
oscillations are observed when VIN is close to OV.
Application Circuit 2
Optocoupler
Rload
GND
8
V
DD
1
PWRGD
R1
487kΩ
ENABLE
+5V
3
2
UV
Cload
R2
6.81kΩ
HV311
DC/DC
PWM
CONVERTER
COM
OV
R3
9.76kΩ
RAMP
V
SENSE GATE
EE
7
4
5
6
C1
10nF
-48V
R4
12.5mΩ
Q1
IRF530
Note: capacitor may be needed to slow PWRGD dv/dt if
oscillations are observed when VIN is close to OV.
Application Circuit 3
11
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