HV310 datasheet(6/6 Pages) SUTEX

6 / 6 page

HV300/HV310

1235 Bordeaux Drive, Sunnyvale, CA 94089

TEL: (408) 744-0100 • FAX: (408) 222-4895

www.supertex.com

08/26/02rev.10b

Typical Application Circuit

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.

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:

off = VUVH = 1.16 = |VEEUV| * (R2+R3) / (R1+R2+R3)

off = VOVL = 1.26 = |VEEOV| * R3 / (R1+R2+R3)

Where

EEUV| and |VEEOV| are Under & Over Voltage Set

points.

If we select a divider current of 100µA at a nominal operating

input voltage of 50 Volts then

(R1+R2+R3) = 50V / 100µA = 500kΩ

From the second equation for an Over voltage set point of 65

Volts the value of R3 may be calculated.

off = 1.26 = 65 * R3 / 500kΩ

R3 = (1.26 * 500K) / 65 = 9.69 kΩ

The closest 1% value is 9.76kΩ.

From the first equation for an Under Voltage set point of 35

Volts the value R2 can be calculated.

off = 1.16 = 35 * (R2 + R3) / 500K

R2 = (1.16 * 500K) / 35 – 9.76kΩ = 6.81kΩ.

The closest 1% value is 6.81kΩ.

Then R1 = 500K – (R2 +R3) = 483kΩ

The closest 1% value is 487kΩ.

Current Limit

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 V

EE pin. For example

to program a current limit of 1A, one would choose a resistor as

follows:

Rsense = 50mV / Isense

Rsense = 50mV / 1A

Rsense = 50mΩ

Undervoltage/Overvoltage Operation

VDD

VEE

SENSE

GATE

RAMP

GND

-48V

50mΩ

487kΩ

6.81kΩ

9.76kΩ

IRF530

Cload

+5V

HV300LG or

HV310LG

COM

DC/DC

PWM

CONVERTER

GND

Jumper

Long

Short

ENABLE

10nF

PWRGD

NOTES: 1. Undervoltage Lockout (UV) set to 35V

2. Overvoltage Lockout (OV) set to 65V

3. Remove Jumper if Short Pin is used

GND

VIN

Pass

Transistor

OFF

UVOFF

UVON

OVOFF

OVON

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