HV300/HV310
Typical Application Circuit
Long
Pin
GND
Jumper
8
Short
Pin
V
DD
GND
PWRGD
1
R1
487kΩ
ENABLE
3
2
UV
OV
+5V
HV300LG or
HV310LG
R2
6.81kΩ
Cload
DC/DC
PWM
CONVERTER
COM
R3
9.76kΩ
RAMP
V
EE
SENSE
GATE
7
4
5
6
NOTES: 1. Undervoltage Lockout (UV) set to 35V
2. Overvoltage Lockout (OV) set to 65V
3. Remove Jumper if Short Pin is used
C1
10nF
Long
Pin
-48V
R4
50mΩ
Q1
IRF530
UVoff = 1.16 = 35 * (R2 + R3) / 500K
R2 = (1.16 * 500K) / 35 – 9.76kΩ = 6.81kΩ.
The closest 1% value is 6.81kΩ.
Application Information
Under Voltage and Over Voltage Detection
The UV and OV pins are connected to comparators with nominal
1.21V thresholds and 100mV of hysteresis (1.21V ± 50mV).
They are used to detect under voltage and over voltage
conditions at the input to the circuit. Whenever the OV pin rises
above its threshold or the UV pin falls below its threshold the
GATE voltage is immediately pulled low, the PWRGD signal is
deactivated and the external capacitor connected to the RAMP
pin is discharged.
Then R1 = 500K – (R2 +R3) = 483kΩ
The closest 1% value is 487kΩ.
The under voltage and over voltage trip points 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:
Undervoltage/Overvoltage Operation
GND
UV
OFF
UV
ON
VIN
UVoff = VUVH = 1.16 = |VEEUV| * (R2+R3) / (R1+R2+R3)
OVoff = VOVL = 1.26 = |VEEOV| * R3 / (R1+R2+R3)
OV
ON
OV
OFF
Where |VEEUV| and |VEEOV| are Under & Over Voltage Set
points.
ON
Pass
Transistor
OFF
If we select a divider current of 100µA at a nominal operating
input voltage of 50 Volts then
(R1+R2+R3) = 50V / 100µA = 500kΩ
Current Limit
From the second equation for an Over voltage set point of 65
Volts the value of R3 may be calculated.
The current limit magnitude above which the current will not be
allowed to rise during startup is programmed using a sense
resistor connected from the SENSE pin to VEE pin. For example
to program a current limit of 1A, one would choose a resistor as
follows:
OVoff = 1.26 = 65 * R3 / 500kΩ
R3 = (1.26 * 500K) / 65 = 9.69 kΩ
The closest 1% value is 9.76kΩ.
Rsense = 50mV / Isense
Rsense = 50mV / 1A
Rsense = 50mΩ
From the first equation for an Under Voltage set point of 35
Volts the value R2 can be calculated.
08/26/02rev.10b
1235 Bordeaux Drive, Sunnyvale, CA 94089
TEL: (408) 744-0100 • FAX: (408) 222-4895
www.supertex.com
©2002 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
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SUPERTEX [ Supertex, Inc ]
