LT4363-1 LINER
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High Voltage Surge Stopper with Current Limit Demonstration Circuit 1935A showcases the L T®4363 surge stopper in a 12V , 2A application. Inputs of up to 80VDC and 1ms transients of up to 250V are limited to 16.3V at the output. The MOSFET is protected against output overloads by current limiting. Sustained overvoltage or overcurrent conditions cause the L T4363 to turn off after a timer delay. The L T4363-1 latches off and is reset by pulling SHDN low for at least 100μs. The L T4363-2 automatically retries after a cool down delay; retry is inhibited if OV is higher than 1.275V . L, L T , L TC, L TM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. By removing 0Ω jumpers R1C and R4C, the operation may be modified for 28V systems with an output regulation point of 34.6V in overvoltage conditions. Design files for this circuit board are available at http://www.linear .com/demo PERFORMANCE SUMMARYTA = 25°C, R1C = R4C = 0Ω (As Shipped) PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supply Operating 5.7 12 14.7 V DC Survival 80 V 1ms T ransient Survival 250 V Output Regulation Voltage 15.7 16.3 17.0 V Undervoltage Threshold 5.2 5.6 5.7 V Retry Inhibit Threshold 14.7 15.5 16.2 V Current Limit 2.0 2.5 3.1 A T A = 25°C, R1C = R4C = Open (Optional Field Change) PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supply Operating 12.4 28 31.6 V DC Survival 80 V 1ms T ransient Survival 250 V Output Regulation Voltage 33.2 34.6 35.9 V Undervoltage Threshold 11.2 11.9 12.4 V Retry Inhibit Threshold 31.6 33.3 34.9 V Current Limit 2.0 2.6 3.1 A
Danger! High voltage testing should be performed by qualified personnel only. As a safety precaution at least two people should be present during high voltage testing. BOARD LAYOUT DC1935A is designed to withstand 250V peak input voltage for up to 1ms. This high voltage is stood off by CSNAB, R4A, R7, R10, Q1, Q2 and Q3. Maximum input voltage is limited by Q1’s 250V BV DSS rating. The permissible time at 250V is limited by R7, which dissipates slightly less than 40W and is capable of doing so for at least 1ms. The minimum spacing is limited by 1206 pad spacing where the gap between solder pads is 2mm, or just under 80mils. Thus, the spacing between the input plane and all other board traces is maintained at a minimum of 2mm. As a point of reference, a 2mm needle gap in air breaks down well above 1kV . 250V CAPABILITY The L T4363 is rated to survive up to 100V . If input spikes did not exceed 100V , the V CC pin could be connected directly to the input. Nevertheless, in some systems input voltage spikes may reach levels much higher than 100V . Opera- tion under these conditions is made possible by limiting the voltage at the V CC pin with an external filter or clamp. The simplest clamp is a Zener diode or transient voltage suppressor (D1) and a 1kΩ series limiting resistance (R7). This arrangement is adequate for millisecond excursions of up to 250V . The voltage is limited by the breakdown of Q1 and the peak voltage rating of R7, and the time is limited by the pulse power capability of R7, D1, and Q1. The OV and UV pins are limited to 100V absolute maximum. Practical divider ratios attenuate peak inputs of 250V to safe levels at the OV and UV pins. For the resistors used in DC1935A, the peak voltage at the UV pin is less than 60V when the input spikes to 250V . If there is an input voltage/ divider ratio combination that leads to greater than 100V at OV or UV , the top of the divider may be moved to the V CC clamp for protection, with a small penalty in accuracy, or a Zener clamp may be added to the affected pin. While the input of the DC1935A can handle 250V , several points should be brought to mind. First, the dissipation of several components rises to significant levels when 250V is applied. R4 dissipation rises to near 500mW , D1 dissipates over 10W and R7 dissipates nearly 40W . These components dissipate high, destructive power even though the L T4363 regulates and then shuts down the output, saving the load and Q1 from destruction. The maximum safe DC input is 80V , limited by the dissipation of R7 and D1. Always remember that 250V should be applied only as a spike or transient, not exceeding 1ms duration. Danger! High voltage testing should be performed by qualified personnel only. As a safety precaution at least two people should be present during high voltage testing. DC1935A-A AND DC1935A–B STUFFING OPTIONS The DC1935A-A is fitted with the L T4363-1 which latches off after a timer delay in the presence of overvoltage or overcurrent conditions. Once latched off the L T4363-1 ver- sion’s timer executes a cool-down cycle, after which the output may be restarted by pulsing the SHDN pin low for at least 100μs, or by briefly disconnecting the input supply. The DC1935A-B is fitted with the L T4363-2 which automati- cally retries after its cool-down cycle. Retry is inhibited by the OV pin, if the input is greater than 15.5V . OPERATION The shutdown pin, SHDN, is floating so that when power is applied to the input, the L T4363 automatically turns on. The L T4363 protects the load from destruction by regulating the output voltage to a safe level during intervals of input overvoltage. DC1935A is designed to regulate the output at 16.3V . If the input voltage is less than 16.3V , power passes through directly to the output. The output voltage is sensed by the R1/R2 divider and the FB pin. The GATE pin controls Q1 to regulate the output voltage in the event the input rises above 16.3V . Overcurrent is sensed by R SNS and the SNS and OUT pins of the L T4363. If the load current reaches 50mV/20mΩ, the GATE pin will control Q1 to regulate the output cur- rent at 2.5A.
cally tries to restart the load after a cool-down interval. from 150μs to 10ms. The cool-down time is 158ms. retry inhibit threshold (OV pin), and 15% for current limit. the demo board for easy reference. OV thresholds, as well as the output regulation voltage. R8, install a PZTA42 for Q2 and increase R7 to 150kΩ. minimum operating voltage, as does the drop in R7.
- Connect short lengths of hook-up wire between
lead to replicate the function of R3.
- Connect the input supply to the MOSFET drain, and
connect the load to the output side of the sense resistor .
- If parasitic oscillations are observed at start-up, or
snubber to the drain of the MOSFET . Figure 1. For High Current Applications Assemble Power Path
regulator are moved off-board to eliminate spacing issues. than 5.6V the output will shut off and D3 will extinguish. It will restart when the input rises above 5.7V . Figure 2. For Higher Input Voltage Operation, Assemble Power Table 1. Test Point Connections
1 Drain/Input —
2 Gate GATE
3 Sense
4 Sense – OUT
5 Ground GND
6 Base Q2, R7 —
7 Emitter Q2 V
trigger output to trigger the oscilloscope sweep. Figure 3. Basic Test Setup
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER 1 2 CTMR, CG CAP ., X7R, 47nF , 100V 20% 0805 AVX, 08051C473MAT2A 2 1 CL CAP ., ALUM., 33μF 50V 20% SMT SUN ELECT ., 50CE33LX 3 1 CSNUB CAP ., X7R, 10nF , 500V 20% 1206 AVX, 12067C103MAT2A 4 1 C2 CAP ., X7R, 100nF , 100V 20% 0805 AVX, 08051C104MAT2A 5 1 C3 CAP ., X7R, 10nF , 100V 20% 0805 AVX, 08051C103MAT2A 6 1 D1 DIODE, TVS, 60V , SMA DIODES/ZETEX, SMAJ60A-13-F 7 1 D2 DIODE, CURRENT LIMITING, SOD-123 CENTRAL SEMI., CMJ2700 TR 8 2 D3, D4 LED, GREEN, SMD PANASONIC, LN1371SGTRP 9 1 Q1 MOSFET , N-CH, 250V , D2-PAK FAIRCHILD, FDB33N25TM 10 1 Q3 TRANSISTOR, NPN, 300V , SOT-223 NXP , PZTA42 11 1 Q4 TRANSISTOR, NPN, 40V , SOT-23 DIODES/ZETEX, MMBT3904-7-F 12 1 RG RES., CHIP , 33Ω, 1/8W , 5% 0805 NIC, NRC10J330TRF 13 1 RSNS RES., CHIP , SENSE, 0.020Ω, 1/4W , 5% 1206 NIC, NCST12JR020JTRF 14 1 RSNUB RES., CHIP , 100Ω, 1/2W , 5% 1210 PULSE PROOF NIC, NRCP25J101TRF 15 1 R1A RES., CHIP , 118k, 1/8W , 1% 0805 NIC, NRC10F1183TRF 16 1 R1B RES., CHIP , 143k, 1/8W , 1% 0805 NIC, NRC10F1433TRF 17 1 R1C, R4C, R8 RES., CHIP , 0Ω, 0805 NIC, NRC10Z0TRF 18 1 R2 RES., CHIP , 10k, 1/8W , 1% 0805 NIC, NRC10F1002TRF 19 1 R3 RES., CHIP , 10Ω, 1/8W , 5% 0805 NIC, NRC10J100TRF 20 1 R4A RES., CHIP , 93.1k, 1/4W , 1% 1206 NIC, NRC12F9312TRF 21 1 R4B RES., CHIP , 140k, 1/8W , 1% 0805 NIC, NRC10F1403TRF 22 0 R7 RES., CHIP , 1k, 1/4W , 5% 1206 PULSE PROOF NIC, NRCP12J102TRF 23 1 R10 RES., CHIP , 270k, 1/4W , 5% 1206 NIC, NRC12J274TRF 24 1 R11 RES., CHIP , 240Ω, 1/8W , 5% 0805 NIC, NRC10J241TRF DC1935A-A 1 1 R5 RES., CHIP , 28k, 1/8W , 1% 0805 NIC, NRC10F2802TRF 2 1 R6 RES., CHIP , 0Ω , 0805 NIC, NRC10Z0TRF 3 1 U1 I.C., HIGH VOL TAGE SURGE STOPPER LINEAR TECH., L T4363IDE-1 DC1935A-B 1 1 R5 RES., CHIP , 18.2k, 1/8W , 1% 0805 NIC, NRC10F1822TRF 2 1 R6 RES., CHIP , 10k, 1/8W , 1% 0805 NIC, NRC10F1002TRF 3 1 U1 I.C., HIGH VOL TAGE SURGE STOPPER LINEAR TECH., L T4363IDE-2
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However , no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. SCHEMATIC DIAGRAM
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com © LINEAR TECHNOLOGY CORPORATION 2012 LT 0412 • PRINTED IN USA DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (L TC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONL Y and is not provided by L TC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the Europ ean Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT , SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further , the user releases L TC fro m all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory co mpliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. L TC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. L TC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product . Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a L TC applica- tion engineer . Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation