HV320

HV320 SUTEX | Alldatasheet

Document overview

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Technical content

Features

! Differential 10V to 90V operation (+VIN / -VEE) ! 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™ 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 UV 5 mOhm 487k OV IRFB4710 Vee Sense Gate HV320 6.81k Vin 10nF GND 9.76 k HV320 Initial Release

Electrical Characteristics (-10 • VEE • -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 VEE = -48V OV and UV Control (Referenced to VEE pin) VUVH UV High Threshold 1.26 V Low to High Transition VUVL UV Low Threshold 1.16 V High to Low Transition VUVHY UV Hysteresis 100 mV IUV UV Input Current 1.0 nA Vuv = VEE + 1.9V @ 25° C VOVH OV High Threshold 1.26 V Low to High Transition VOVL OV Low Threshold 1.16 V High to Low Transition VOVHY OV Hysteresis 100 mV IOV OV Input Current 1.0 nA VOV = VEE + 0.5V @ 25° C Circuit Breaker (VUV = VEE + 1.9V, VOV = VEE + 0.5V, External MOSFET is IRFFR120N) VSENSE-CB Circuit Breaker Threshold Voltage 100 120 mV Referenced to VEE pin @ 25° C tCBTRIP Circuit Breaker Delay Time 2.0 5.0 µs May be extended by external RC circuit ISENSE-CB 1.0 nA VSENSE-CB = 100mV @ 25° C IRFB4710 and IRFFR120 are registered trademarks of International Rectifier. Raychem and PolySwitch are registered trademarks of Tyco International.

Ordering Information

8 Pin SO

Absolute Maximum Ratings* Vee referenced to Vin pin +0.3V to -100V VUV and VOV 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.

Gate Drive Output (Referenced to VEE pin, External MOSFET is IRFB4710*) VGATE Maximum Gate Drive Voltage 8.5 V VUV = Vee +1.9V, VOV = Vee +0.5V IGATEUP Gate Drive Pull-Up Current 500 µA VUV = Vee +1.9V, VOV = Vee +0.5V IGATEDOWN Gate Drive Pull-Down Current mA VUV = Vee, VOV = Vee +0.5V VGATELOW Minimum Gate Drive Voltage 400 mV VUV = Vee, VOV = Vee +0.5V, Igate = 5mA Dynamic Characteristics (See timing below, External MOSFET is IRFB4710) tGATEHLOV OV High to GATE Low 500 ns Pulsed VOV from VEE+0.5V to VEE +1.9V tGATEHLUV UV Low to GATE Low 500 ns Pulsed VUV from VEE+1.9V to VEE +0.5V Pinout for LG Top View Gate UV OV Sense Vee NC NC 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. VEE – This pin is the negative terminal of the power supply input to the circuit. VIN --- 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 VEE Pin programs the circuit breaker trip threshold. tGATEHLUV tGATEHLOV Vuvl Vgate Vovh Vgate VUV VOV

& POR Logic Sense OV 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 5µs 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

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: UVOFF = VUVL = 1.16 = •VEEUV(off)•x (R2+R3)/(R1+R2+R3) OVOFF = VOVL = 1.26 = •VEEOV(off)•x R3/(R1+R2+R3) Where •VEEUV(off)•and •VEEOV(off)• relative to VEE are Under and Over Voltage Shut Down Threshold points. If we select a divider current of 100µA 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. OVOFF = 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. UVOFF = 1.16 = 35 x (R2+R3) / 500k 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: UVON = VUVH = 1.26 = •VEEUV(on) •x (R2+R3)/(R1+R2+R3) OVON = VOVL = 1.16 = •VEEOV(on) •x R3/(R1+R2+R3) Where •VEEUV(on) • and •VEEOV(on) • are Under and Over Voltage Start Up Threshold points relative to Vee. Then

• VEEUV(on) • = 1.26 x (R1+R2+R3)/(R2+R3) = 38.29V and
• VEEOV(on) •= 1.16 x (R1+R2+R3)/R3 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 VEE. The value of this cap can be calculated accordingly: VC1 ( t ) = VIN x ( 1 – e Where VC1= 1.26 VIN = 1.60V tPOR = desired POR time to overcome the bounce Req = R1 ⎢⎢ (R2 + R3) From the above C1 can be calculated: tPOR Req x 1.60 For example for tPOR = 10ms and Values show on Page 1, the C1 calculates to be: 487 + 6.81 + 9.76 10 x 10 16000 x 1.60 C1 ≅ .39µF a .47µF can be used. Under Voltage/Over Voltage Operation GND UVOFF UVON Vin OVON OVOFF Pass Transistor ON OFF Req = = 16K C1 = C1 = -tPOR Req x C1 )

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 * (Rθjc + Rθcs + Rθsa) + TA ≤ Tj_derated Rθsa ≤ 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 VEE 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 / ITRIP = 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: PRSENSE = (VSENSE-CB max) / R-sense = (0.12) 2 / 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 = (ICBmax^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 Rθjc = 0.74°C/W and Rθcs = 0.5°C/W and the maximum operating temperature being 55°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 VEE 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 VEE pin to the respective ends of the current sense resistor is recommended. To Vee Pin To Sense Pin To Negative Terminal of Power Source To Source of MOSFET Sense Resistors

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 VEE pin to filter the voltage spikes. 9.76 k 10nF LOAD UV Vee IRFB4710 GND HV320 5 mOhm -48V Application Circuit 1 Sense 487k 6.81k Gate OV 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 OV -48V GND IRFB4710 Application Circuit 2 Sense Vin R HV320 16.2k 5 mOhm Vee UV 475k Gate LOAD 511k

Extending Circuit Breaker Delay Connecting a resistor in series with the SENSE pin and a capacitor between the SENSE and VEE pins as shown in the following diagram may be used to extend the Circuit Breaker delay time beyond the 5µs internally set delay time. HV320 -48V OV 6.81k R LOAD 487k Sense Gate Vee 9.76 k Vin UV 10nF C Application Circuit 3 GND 5 mOhm IRFB4710 Supertex inc. ©2003 Supertex Inc. All rights reserved. Unauthorized use ofr reproduction prohibited.

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