HV320
(UVLO) has been satisfied, the circuit checks the input
supply under voltage (UV) and over voltage (OV) sense
circuits to ensure that the input voltage is within
programmed limits. These limits are determined by the
selected values of resistors R1, R2 and R3 that form a
voltage divider. Once the input voltage is within the
programmed limits, the controller will force the GATE
terminal to nominal 10V and the circuit breaker supervisor
is enabled.
When the voltage on the SENSE pin rises to 100mV,
indicating an over current condition, the circuit breaker will
trip in less than 5
µ
s. This time may be extended by the
addition of external components (refer to Application
Circuit 3 on page 9). The gate voltage is latched off when
an over current condition is detected and is reset by
removal and reapplication of input power.
At any time during the start up cycle or thereafter, crossing
the UV and OV limits (including hysteresis) will cause an
immediate reset of all internal circuitry. When the input
supply voltage returns to a value within the programmed
UV and OV limits, a new start up sequence will be
initiated.
Safety recommendation:
For safety critical applications
where UL, CSA or other safety agency approvals are
required, a fuse must be placed in series with HV320.
Although HV320 will protect a fuse from opening in many
instances, from the safety agency point of view, ICs
cannot displace a fuse.
Test Set Up Circuit
GND
Vin
R1
487k
100uF
100V
R2
6.81k
OV
Vee
R3
9.76 k
C1
Sense
R5
1k
C2
10nF
IRFR120
Gate
Output Short Circuit Switch
UV
HV320
Load
-48V
R4
50 mOhm
Waveforms
Vgs
5V/div
Steady state operation
followed by a lead short
FET
Current
2V/div
FET
Current
1V/div
Figure 1
Figure 2
5
SUPERTEX [ Supertex, Inc ]
