Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate
"products liability indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined
to be defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest
product specifications, refer to the Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current data book or to the
Legal/Disclaimer page on the Supertex website.

Accurate, Re-Settable Electronic Circuit Breaker

(Negative Supply Rail)

Features

Differential 10V to 90V operation (+V

/ -V

)

UV and OV Lock Out

Power-On-Reset (POR) for debouncing

Sense resistor programs circuit breaker

Noise filter prevents false trip

Programmable circuit breaker trip time

Latched Operation

Low Power, <0.4mA

Small SO-8 package

Applications

-48V Central Office Switching

-24V Cellular and Fixed Wireless Systems

-24V PBX Systems

Telecom Line Cards

-48V Powered Ethernet for VoIP

Distributed Power Systems

Power Supply Input/Output Fault Isolator

Electronic Circuit Breaker

Servers and SANS replaceable modules

Automotive and Industrial Circuit Breakers

BUS Networks (CAN BUS, etc.)

General Description

The Supertex HV320 re-settable electronic circuit breaker is
designed to provide fast, consistent and accurate current
limiting and load isolation during fault conditions. It may be
used in a variety of applications in such markets as telecom,
power, automotive, industrial, medical and security as well
as in systems where active control is implemented in the
negative supply lead. The current trip threshold is
programmed by a sense resistor and operates from voltages
ranging from 10V to 90V differentially.

The HV320 can easily replace popular positive temperature
coefficient (PTC) products such as Raychem

PolySwitches

TM or re-settable polyfuses. HV320 overcomes

numerous performance shortcomings of existing PTC's,
including trip point inaccuracy, increased device resistance
after initial reset, slow response time, susceptibility to
temperature variations and very high trip current to
operating current.

During initial application of power, the gate of the external
pass device is clamped low to suppress contact bounce
glitches. Thereafter, the UV/OV supervisors and power-on
reset work together to suppress gate turn on until the input
power bounce ends. Once ON, HV320 continues to monitor
the input voltage and the load current level. If a load fault
occurs, the electronic circuit breaker will trip and the pass
element will be turned off. To restart, the UV or OV pins
must be toggled (for example by resetting the input voltage).

Typical Application Circuit

-48V

Load

5 mOhm

487k

IRFB4710

Vee

Sense

Gate

HV320

6.81k

Vin

10nF

GND

9.76 k

HV320

Initial Release

HV320

Electrical Characteristics

(-10 · V

· -90V, -40°C · T · +85°C unless otherwise noted)

AC Characteristics

Symbol Parameter Min

Typ

Max

Units

Conditions

Supply

(Referenced to Vin Pin)

Vee Supply

Voltage

-90 -10 V

Iee Supply

Current

400

450

µA V

= -48V

OV and UV Control

(Referenced to V

pin)

UVH

UV High Threshold

1.26

Low to High Transition

UVL

UV Low Threshold

1.16

High to Low Transition

UVHY

Hysteresis

100 mV

UV Input Current

1.0

Vuv = V

+ 1.9V @ 25

° C

OVH

OV High Threshold

1.26

Low to High Transition

OVL

OV Low Threshold

1.16

High to Low Transition

OVHY

Hysteresis

100 mV

OV Input Current

1.0

= V

+ 0.5V @ 25

° C

Circuit Breaker

= V

+ 1.9V, V

= V

+ 0.5V, External MOSFET is IRFFR120N)

SENSE-CB

Circuit Breaker Threshold Voltage

100

120

Referenced to V

pin @ 25

CBTRIP

Circuit Breaker Delay Time

2.0

5.0

µs

May be extended by
external RC circuit

SENSE-CB

1.0

SENSE-CB

= 100mV @ 25

° C

IRFB4710 and IRFFR120 are registered trademarks of International Rectifier.

Raychem and PolySwitch are registered trademarks of Tyco International.

Ordering Information

Package Option

DEVICE

8 Pin SO

HV320 HV320LG

Absolute Maximum Ratings*

Vee referenced to Vin pin

+0.3V to -100V

and V

referenced to Vee Voltage

-0.3V to +12V

Operating Ambient Temperature

-40°C to +85°C

Operating Junction Temperature

-40°C to +125°C

Storage Temperature Range

-65°C to +150°C

*Absolute Maximum Ratings are those values beyond which damage to the
device may occur. Functional operation under these conditions is not
implied. Continuous operation of the devide at the absolute rating level may
affect device reliability. All voltages are referenced to device ground.

HV320

Gate Drive Output

(Referenced to V

pin, External MOSFET is IRFB4710*)

GATE

Maximum Gate Drive Voltage

8.5

= Vee +1.9V,

= Vee +0.5V

GATEUP

Gate Drive Pull-Up Current

500

µA

= Vee +1.9V,

= Vee +0.5V

GATEDOWN

Gate Drive Pull-Down Current

= Vee,

= Vee +0.5V

GATELOW

Minimum Gate Drive Voltage

400

= Vee,

= Vee +0.5V, Igate = 5mA

Dynamic Characteristics

(See timing below, External MOSFET is IRFB4710)

GATEHLOV

OV High to GATE Low

500

Pulsed V

from V

+0.5V to V

+1.9V

GATEHLUV

UV Low to GATE Low

500

Pulsed V

from V

+1.9V to V

+0.5V

Pinout for LG

Top View

Gate

3
4

Sense

Vee

Vin

Pin Description

OV --- This Over Voltage (OV) sense pin, when raised above its high threshold limit, will immediately cause the GATE pin to be
pulled low. The GATE pin will remain low until the voltage on this pin falls below the low threshold limit, initiating a new start-up
cycle.

UV This Under Voltage (UV) sense pin, when below its low threshold limit, will immediately cause the GATE pin to be pulled
low. The GATE pin will remain low until the voltage on this pin rises above the high threshold limit, initiating a new start-up
cycle.

V

This pin is the negative terminal of the power supply input to the circuit.

--- This pin is the positive terminal of the power supply input to the circuit.

GATE --- This is the Gate Driver Output for the external N-Channel MOSFET.

SENSE --- The current sense resistor connected from this pin to the V

Pin programs the circuit breaker trip threshold.

GATEHLUV

GATEHLOV

Vuvl

Vgate

Vovh

Vgate

HV320

Functional Block Diagram

Vee

Gate

100mV

Vin

buffer

Vbg

UVLO

Regulator

& POR

Logic

Sense

Functional Description

HV320 as a fuse and circuit breaker replacement:
Telecom, data networks, automotive, industrial controls
and some computer applications require the ability to
isolate the power source from a load fault without having
to physically replace a fuse or manually reset a
mechanical circuit breaker. Traditionally a fast acting fuse
or Positive Temperature Coefficient (PTC) device such as
Raychem's

PolySwitch or a manual / thermal circuit

breaker have been used to limit the fault current.

The problems with PTCs are numerous. First, they are
extremely temperature dependent. For example the
required trip current can vary as high as 150% of nominal
value at lower temperatures such as 40

°C and as low as

50% of nominal value at higher temperatures such as
+85

°C.

Second, the ratio of trip current to steady state current can
range from 7 to 70. This implies for an application where
steady state current is 4A, traces must be over designed
to withstand the trip current of 100A, a ratio of 25:1. Third,
PTC's once tripped, require 20 seconds to minutes to
reset and even when they are reset, the resistance value
can permanently change as much as 240%. This implies
PTC's are not suitable for repeated short circuit
applications. Lastly the surface mount PTCs typically have
large end cap terminations that absorb heat during the
reflow process and can result in insufficient solder and
cold solder joints. It is not uncommon for PCB surface
contaminations to be present, thus resulting in poor
solderability, hence loss of yield.

Typically, fuses are rated in Amp^2-seconds. For a SMT
1206 size fast-acting 2A, 63V fuse rated at 0.23 A - square

second, it could take more than 200A for 5

µs before the

fusing element melts.

HV320 is an ideal alternative to thermal and manual circuit
breakers in DC input applications. It has wide variety of
uses in the automotive industry, such as PCB trace /
device protection and DC motors and solenoid actuator
current limit protection. These devices are typically used in
windows and seat adjustment operations as well as
automatic trunk opening mechanisms. Since these
devices are operated manually, they can remain energized
by the operator even after the mechanical lever has
reached its end of travel. In this case, back EMF that
normally opposes the supply voltage will drop to zero and
a large current surge can begin to flow. HV320 can
accurately be programmed to trip the current. In industrial
applications, HV320 can offer broad solutions in DC
solenoid-operated valves, DC motors and other
electromagnetic loads.

Fault current magnitude can be scaled to different current
ratings by proper selection of the sense resistor and the
external N-Channel MOSFET. For higher current
applications, IGBT devices may be considered. The
HV320 is intended to provide this circuit breaker function
on supply rails in the range of

-10 to -90 Volts.

Description of Operation
During initial application of power, a unique proprietary
circuit holds off the external MOSFET, preventing an input
glitch while an internal regulator establishes an internal
operating voltage of approximately 10V. Until the proper
internal voltage is achieved, all circuits are held reset and
the gate to source voltage of the external MOSFET is
clamped low. Once the internal under voltage lock out

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

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

6.81k

GND

9.76 k

Sense

HV320

IRFR120

487k

10nF

100V

100uF

Vee

Load

Vin

50 mOhm

Gate

-48V

Output Short Circuit Switch

Waveforms

Figure 1

Figure 2

Vgs
5V/div

FET
Current
2V/div

FET
Current
1V/div

Steady state operation
followed by a lead short

HV320

Design Information

Setting Under Voltage and Over Voltage Shut Down
The UV and OV pins are connected to comparators with
typical 1.26V thresholds and 100mV of hysteresis. They
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.

Calculations can be based on either the desired input
voltage operating limits or the input voltage shutdown
limits. In the 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:

UV

OFF

= V

UVL

= 1.16 = ·V

EEUV(off)

·x (R2+R3)/(R1+R2+R3)

OFF

= V

OVL

= 1.26 = ·V

EEOV(off)

·x R3/(R1+R2+R3)

Where ·V

EEUV(off)

·and ·V

EEOV(off)

· relative to V

are Under and

Over Voltage Shut Down Threshold points.

If we select a divider current of 100

µA at a nominal

operating input voltage of 50 Volts, then

R1+R2+R3 = 50V/100uA = 500k Ohm

From the second equation, for an OV shut down threshold
of 65V, the value of R3 may be calculated.

OV

OFF

= 1.26 = (65xR3)/500k

R3 = (1.26x 500k)/65 = 9.69k

The closest 1% value is 9.76k Ohm.

From the first equation, for a UV shut down threshold of
35V, the value of R2 can be calculated.

UV

OFF

= 1.16 = 35 x (R2+R3) / 500k

R2 = ((1.16 x 500k)/35) 9.76k = 6.81k

The closest 1% value is 6.81k Ohm.

Then

R1 = 500k R2 R3 = 483k Ohm.

The closest 1% value is 487K Ohm.

From the calculated resistor values the OV and UV start
up threshold voltages can be calculated as follows:

UV

= V

UVH

= 1.26 = ·V

EEUV(on)

·x (R2+R3)/(R1+R2+R3)

= V

OVL

= 1.16 = ·V

EEOV(on)

·x R3/(R1+R2+R3)

Where ·V

EEUV(on)

· and ·V

EEOV(on)

· are Under and Over

Voltage Start Up Threshold points relative to Vee.

Then

·V

EEUV(on)

· = 1.26 x (R1+R2+R3)/(R2+R3)

·V

EEUV(on)

·= 1.26 x (487k+6.81k+9.76k)/(6.81k+9.76k )

= 38.29V

and

·V

EEOV(on)

·= 1.16 x (R1+R2+R3)/R3

·V

EEOV(on)

·= 1.16 x (487k +6.81k +9.76k)/9.76k = 59.85V

Therefore, the circuit will start when the input supply
voltage is in the range of 38.29V to 59.85V. To overcome
longer bounce time during insertion, POR time must be
extended. An additional cap C1 (Page 1) must be added
from the UV pin to V

. The value of this cap can be

calculated accordingly:

VC1 ( t ) = V

(

1 e

)

Where

VC1= 1.26
V

= 1.60V

POR

= desired POR time to overcome the bounce

Req = R1

(R2 + R3)

From the above C1 can be calculated:

POR

Req x 1.60

For example for t

POR

= 10ms and

Values show on Page 1, the C1 calculates to be:

487 x (6.81 + 9.76)

487 + 6.81 + 9.76

10 x 10

-3

16000 x 1.60

.39µF

a .47

µF can be used.

Under Voltage/Over Voltage Operation

GND

UV

OFF

Vin

OFF

Pass
Transistor ON
OFF

(

Req =

= 16K

C1 =

-t

POR

Req x C1

)

HV320

Start Up Overload Protection
If there is an output overload or short circuit during start
up, the circuit breaker will trip when the voltage at the
sense pin reaches 100mV. The gate is clamped low
indefinitely until input power is cycled, the UV pin is pulsed
low (<1.16V), or the OV pin is pulsed high (>1.26V). See
Figure 2 on Page 5.

Pd * (R

jc + Rcs + Rsa) + TA Tj_derated

11.3 * (0.74 + 0.5 +R

sa) + 55°C 150°C

sa 7°C

Circuit Breaker

The circuit breaker will trip in less than 5µs when the
voltage on the SENSE pin reaches a nominal 100mV. A
resistor in series with the SENSE pin and a capacitor
connected between the SENSE and V

pins may be

added to delay the rate of voltage rise on the SENSE pin,
thus permitting a current overshoot and delaying Circuit
Breaker activation. See Figure 1 on Page 5.

Selection of External R_sense
As a design example, consider a 500W load of a 48V
rectifier: at a minimum regulation voltage of -42V, the
input current is 11.9A, assuming that the trip point is set
for 16A, the value of the sense resistor.

R_sense = 80mV / I

TRIP

= 0.08/16 = 0.005 Ohm

Where 80mV is the minimum circuit breaker trip level,
the maximum circuit breaker threshold is 120mV. This will
make the current trip level at 24A.

The power dissipation of the sense resistor is:

RSENSE

= (V

SENSE-

CB max)

/ R-sense = (0.12)

/ 0.005

= 2.88W

Two 0.01 Ohm, 2W, 2512 size SMT resistor may be used
in parallel. See Kelvin Connection to Sense Resistor.

Selection of External Pass Devices

The N-Channel may be selected based on maximum input
operating voltage, RDS, maximum operating load current
and peak short circuit current.

Continuing with the example, the lowest Rds(on)
International Rectifier N-Channel MOSFET at 100V Vdss
is 14 m-Ohm. The IRFB4710* (TO-220) may be used for
this application.

FET Power Dissipation = (I

CBmax

^2) x Rds(on) x K = 24^2 x

0.014 x 1.4 = 11.3W

The K=1.4 factor is increased Rdson with respect to
temperature rise. Assuming R

jc = 0.74°C/W and Rcs =

0.5

°C/W and the maximum operating temperature being

°C, then the needed heat sink thermal resistance can

be calculated per:

Kelvin Connection to Sense Resistor
Physical layout of the printed circuit board is critical for
correct current sensing. Ideally trace routing between the
current sense resistor and the V

and SENSE pins should

be direct and as short as possible with zero current in the
sense traces. The use of Kelvin Connection from SENSE
pin and V

pin to the respective ends of the current sense

resistor is recommended.

To
Vee
Pin

To
Sense

To Negative
Terminal of
Power Source

To Source
of MOSFET

Sense Resistors

HV320

Filtering Voltage Spikes on the Input Supply

In some systems over voltage spikes of very short duration may exist and can prematurely trip the circuit breaker. For these
systems a small capacitor may be added from the OV pin to the V

pin to filter the voltage spikes.

9.76 k

10nF

LOAD

Vee

IRFB4710

GND

HV320

5 mOhm

-48V

Application Circuit 1

Sense

487k

6.81k

Gate

Vin

Increasing Under Voltage Hysteresis

If the internally fixed under voltage hysteresis is insufficient for a particular system application, then it may be increased by
using separate resistor dividers for OV and UV and providing a resistor feedback path from the gate pin to the UV pin.

10k

10nF

-48V

GND

IRFB4710

Application Circuit 2

Sense

Vin

HV320

16.2k

5 mOhm

Vee

475k

Gate

LOAD

511k

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: HV320

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: HV320