HV302 Supertex Inc, HV302 Datasheet - Page 6

• Manufacturer Part Number: HV302
• Description: Sequencing Hotswap Controllers
• Manufacturer: Supertex Inc

Design Information
Programming Under and Over Voltage Shut Down
The UV and OV pins are connected to comparators with nominal
1.21V thresholds and 100mV of hysteresis (1.21V
are used to detect under voltage and over voltage conditions at the
input to the circuit. Whenever the OV pin rises above its high
threshold (1.26V) or the UV pin falls below its low threshold
(1.16V) the GATE voltage is immediately pulled low, the PWRGD
pin changes to its inactive state and the external capacitor
connected to the RAMP pin is discharged.
Calculations can be based on either the desired input voltage
operating limits or the input voltage shutdown limits.
following equations the shutdown limits are assumed.
The under voltage and over voltage shut down thresholds can be
programmed by means of the three resistor divider formed by R1,
R2 and R3. Since the input currents on the UV and OV pins are
negligible the resistor values may be calculated as follows:
Where V
Down Threshold points.
If we select a divider current of 100 A at a nominal operating input
voltage of 50 Volts then
From the second equation for an OV shut down threshold of 65V
the value of R3 may be calculated.
The closest 1% value is 9.76k
From the first equation for a UV shut down threshold of 35V the
value of R2 can be calculated.
The closest 1% value is 6.81k
Then
The closest 1% value is 487k
UV
OV
R1
OV
R3
UV
R2
R1
OFF
OFF
OFF
OFF
Supertex, Inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: [phone] Fax: [phone] www.supertex.com
EEUV(off)
R2
1.16
500KΩ
1.26
1.26
1.16
V
V
UVL
OVH
R3
35
65
500kΩ
500KΩ
and V
R2
1.16
65
1.26
500kΩ
35
100uA
50V
500KΩ
R3
R3
9.76kΩ
EEOV(off)
R2
9.69kΩ
V
V
EEUV(off)
EEOV(off)
483kΩ
500kΩ
R3
are Under & Over Voltage Shut
6.81kΩ
R1
R1
R2
R2
R2
R3
R3
R3
R3
50mV). They
In the
6
From the calculated resistor values the OV and UV start up
threshold voltages can be calculated as follows:
Where V
Up Threshold points.
Then
And
Therefore, the circuit will start when the input supply voltage is in
the range of 38.29V to 59.85V.
UV
OV
V
V
V
V
EEUV(on)
EEUV(on)
EEOV(on)
EEOV(on)
ON
ON
EEUV(on)
V
V
Under Voltage/Over Voltage Operation
UVH
OVL
1.26
1.16
1.26
1.16
and V
Rev. D
1.26
1.16
487kΩ
R1
R1
487kΩ
EEOV(on)
R2
6.81kΩ
V
R2
V
R3
R2
EEUV(on)
EEOV(on)
R3
6.81kΩ
6.81kΩ
9.76kΩ
R3
R3
are Under & Over Voltage Start
9.76kΩ
R1
R1
R2
9.76kΩ
9.76kΩ
HV302 / HV312
R2
R2
R3
R3
R3
R3
38.29V
04/17/02
59.85V