1642A

LTC1642A LINER

Document overview

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Technical content

■ Adjustable Undervoltage and Overvoltage Protection ■ Foldback Current Limit ■ Adjustable Current Limit Time-Out ■ VCC: 2.97V to 16.5V Normal Operation, Protected Against Surges to 33V ■ Single Channel NFET Driver ■ Latch Off or Automatic Retry on Current Fault ■ Driver for SCR Crowbar on Overvoltage ■ Adjustable Reset Timer ■ Reference Output with Uncommitted Comparator ■ 16-Pin SSOP Package ■ Hot Board Insertion ■ Electronic Circuit Breaker ■ InfiniBand TM Systems 1N4705 18V 12V BACKPLANE (SHORT PIN) PLUG-IN CARD VCC SENSE GATE GND BRK TMR LTC1642A RST TMR ON FAULT OV RESET FB CRWBR COMP+ COMP– 0.33µF 0.33µF 2N2222 MCR 12DC REF 0.1µF 2.87k 110k 100Ω 107k 13k FDS6630A 0.01µF 0.047µF CLOAD 12V AT 2.5A 330Ω 0.010Ω 11.3k POWER-GOOD = 11.4V 1642a TA01 COMPOUT GND UV = 10.8V OV = 13.2V APPLICATIO SU

FEATURES

1642A is a 16-pin Hot Swap TM controller that allows a board to be safely inserted and removed from a live backplane. Using an external N-Channel pass transis- tor, the board supply voltage can be ramped up at an adjustable rate. A high side switch driver controls the N-Channel gate for supply voltages ranging from 2.97V to 16.5V. The SENSE pin allows foldback limiting of the load current, with circuit breaker action after an adjustable delay time. The delay allows the part to power-up in current limit. The CRWBR output can be used to trigger an SCR for crowbar protection of the load if the input supply exceeds an adjustable threshold. The RESET output can generate a system reset with adjustable delay when the supply volt- age falls below an adjustable threshold. The ON pin cycles the board power. The LTC1642A is available in the 16-pin SSOP package. DESCRIPTIO U , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Hot Swap is a trademark of Linear Technology Corporation.

ON, FB, OV, COMP +, COMP – Operating Temperature Range ABSOLUTE AXI U RATI GSW WW U PACKAGE/ORDER I FOR ATIOUU W (Note 1) ORDER PART NUMBER LTC1642ACGN LTC1642AIGNConsult LTC Marketing for parts specified with wider operating temperature ranges. TJMAX = 150°C, θJA = 130°C/W DC ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCC Operating Voltage Range ● 2.97 16.5 V ICC VCC Supply Current ON = V CC ● 1.25 3.0 mA VLKHI VCC Undervoltage Lockout V CC Rising ● 2.55 2.73 2.95 V VLKLO VCC Undervoltage Lockout V CC Falling ● 2.35 2.50 2.95 V VLKHYST VCC Undervoltage Lockout Hysteresis 230 mV VFB FB Pin Voltage Threshold FB Falling ● 1.208 1.220 1.232 V ∆VFB FB Pin Threshold Supply Variation FB Falling, 2.97V ≤ VCC ≤ 16.5V ● 51 5 m V VFBHST FB Pin Voltage Threshold Hysteresis 3 mV IFB(IN) FB Pin Input Current V OV = 5V ● 0 ±1 µA VOV OV Pin Voltage Threshold OV Rising ● 1.208 1.220 1.232 V ∆VOV OV Pin Threshold Supply Variation OV Rising, 2.97V ≤ VCC ≤ 16.5V ● 51 5 m V VOVHYST OV Pin Voltage Theshold Hysteresis 3 mV IOV(IN) OV Pin Input Current V FB = 5V ● 0 ±1 µA VRST RST TMR Pin Voltage Threshold RST TMR Rising ● 1.200 1.220 1.250 V ∆VRST RST TMR Pin Threshold Supply Variation RST TMR Rising, 2.97V ≤ VCC ≤ 16.5V ● 51 5 m V IRST RST TMR Pin Current Timer On ● –1.5 –2.0 –2.5 µA Timer Off, VRSTTMR = 1.5V 10 mA VBRK BRK TMR Pin Voltage Threshold BRK TMR Rising ● 1.200 1.220 1.250 V ∆VBRK BRK TMR Pin Threshold Supply Variation BRK TMR Rising, 2.97V ≤ VCC ≤ 16.5V ● 51 5 m V IBRK BRK TMR Pin Current Timer On ● –15 –20 –30 µA Timer Off, VBRKTMR = 1.5V 10 mA VCR CRWBR Pin Voltage Theshold CRWBR Rising ● 375 410 425 mV ∆VCR CRWBR Pin Threshold Supply Variation 2.97V ≤ VCC ≤ 16.5V ● 41 5 m V ICR CRWBR Pin Current CRWBR On, V CRWBR = 0V ● –30 –45 –60 µA CRWBR On, VCRWBR = 2.1V ● –1000 –1500 µA CRWBR Off, VCRWBR = 1.5V 2.3 mA The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise specified. GN PART MARKING 1642A 1642AI TOP VIEW CRWBR BRK TMR RST TMR ON RESET FAULT FB GND V CC SENSE GATE REF COMP COMP+ COMPOUT OV GN PACKAGE 16-LEAD PLASTIC SSOP Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/

VCB Circuit Breaker Trip Voltage V CB = (VCC – VSENSE), VFB = GND ● 15 25 36 mV VCB = (VCC – VSENSE), VFB = 1V ● 45 52.5 60 mV 2.97V ≤ VCC ≤ 16.5V, VCB = (VCC – VSENSE), VFB = GND ● 12 25 39 mV VCB = (VCC – VSENSE), VFB = 1V ● 42 52.5 63 mV ISENSE SENSE Pin Input Bias Current V CC = VSENSE = 16.5V ● 0.5 µA IGATE GATE Pin Output Current Charge Pump On, V GATE = GND ● –2 0 –2 5 –3 0 µA Charge Pump Off, VGATE = 5V 10 mA ∆VGATE External N-Channel Gate Drive V GATE – VCC, VCC = 2.97V ● 4.5 5.9 8.0 V VGATE – VCC, VCC = 5V ● 10 11.5 14 V VGATE – VCC, VCC = 15V (0°C to 70°C) ● 6.5 8.5 18 V VGATE – VCC, VCC = 15V (–40°C to 85°C) ● 6 8.5 18 V VONHI ON Pin Threshold ON Rising 1.30 1.34 1.38 V VONLO ON Pin Threshold ON Falling ● 1.20 1.22 1.26 V VONHYST ON Pin Hysteresis 110 mV ION(IN) ON Pin Input Current V ON = 5V ● 0 ±1 µA VOL Output Low Voltage RESET, FAULT, COMPOUT I OL = 1.54mA ● 0.4 V RESET, FAULT IO = 5mA 2 V IPU Logic Output Pull-Up Current RESET, FAULT = GND – 15 µA VREF Reference Output Voltage No Load ● 1.208 1.220 1.232 V ∆VLNR Reference Supply Variation 2.97V ≤ VCC ≤ 16.5V, No Load ● 51 5 m V ∆VLDR Reference Load Regulation I O = 0mA to –1mA, Sourcing Only ● 2.5 7.5 mV IRSC Reference Short-Circuit Current V REF = 0V 4.5 mA VCOS Comparator Offset Voltage V CM = VREF ● ±10 mV VCHYST Comparator Hysteresis V CM = VREF 3m V DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. TYPICAL PERFOR A CE CHARACTERISTICSUW TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 ∆VGATE (V) 1642a G03 VCC = 12V VCC = 5V VCC = 15V VCC = 3V ∆VGATE vs Temperature TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 IGATE (µA) 1642a G04 VGATE = 0V VCC = 3V VCC = 5V VCC = 12V VCC = 15V IGATE vs Temperature VCC (V) 3 6 9 12 15 ∆VGATE (V) 1642a G26 TA = 25°C ∆VGATE vs VCC

TYPICAL PERFOR A CE CHARACTERISTICSUW TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 FB THRESHOLD VOLTAGE (V) 1642a G06 1.226 1.224 1.222 1.220 1.218 1.216 1.214 VCC = 5V FB FALLING FB RISING TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 OV THRESHOLD VOLTAGE (V) 1642a G07 1.226 1.224 1.222 1.220 1.218 1.216 1.214 VCC = 5V OV FALLING OV RISING OV Threshold Voltage vs Temperature FB Threshold Voltage vs Temperature VCC (V) 3 6 9 12 15 CRWBR DRIVER CURRENT (mA) 1642a G35 2.0 1.6 1.2 0.8 0.4 TA = 25°C CRWBR Driver Current vs VCC VCC (V) 3 6 9 12 15 FB THRESHOLD VOLTAGE (V) 1642a G27 1.232 1.228 1.224 1.220 1.216 1.212 1.208 FB RISING FB FALLING TA = 25°C FB Threshold Voltage vs VCC OV Threshold Voltage vs VCC VCC (V) 3 6 9 12 15 OV THRESHOLD VOLTAGE (V) 1642a G28 1.232 1.228 1.224 1.220 1.216 1.212 1.208 OV RISING OV FALLING TA = 25°C TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 CRWBR DRIVER CURRENT (mA) 1642a G13 1.45 1.44 1.43 1.42 1.41 1.40 1.39 1.38 VCC = 5V CRWBR Driver Current vs Temperature TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 CRWBR–TMR THRESHOLD VOLTAGE (mV) 1642a G05 405 404 403 402 401 400 399 398 397 396 395 VCC = 5V CRWBR-TMR Threshold Voltage vs Temperature VCC (V) 3 6 9 12 15 IGATE (µA) 1642a G23 VGATE = 0V TA = 25°C IGATE Pull-Up Current vs VCC VGATE (V) 04 8 12 16 20 24 IGATE (A) 1642a G36 128 112 VCC = 12VTA = 25°C VCC = 3.3V VCC = 5V GATE Pull-Down Current (Current Limit Active)

VCC (V) 02 5 5 0 ICC (mA) 1642a G25 VON = 5V TA = 25°C VON = 0V TYPICAL PERFOR A CE CHARACTERISTICSUW ICC vs VCC ON Pin Threshold Voltage vs Temperature TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 ON PIN THRESHOLD VOLTAGE (V) 1642a G22 1.40 1.36 1.32 1.28 1.24 1.20 VCC = 12V ON RISING ON FALLING VCC (V) 3 6 9 12 15 VREF (V) 1642a G24 1.232 1.228 1.224 1.220 1.216 1.212 1.208 TA = 25°C VREF vs VCC VCC (V) 3 6 9 12 15 PULL-UP CURRENT (µA) 1642a G14 160 140 120 100 TA = –55°C TA = 125°C TA = 25°C TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 VOLTAGE (mV) 1642a G16 600 500 400 300 200 100 VCC = 12V VCC = 5V VCC = 15V VCC = 3V IOL = 1.54mA TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 VOLTAGE (V) 1642a G17 3.5 3.0 2.5 2.0 1.5 1.0 0.5 VCC = 12V VCC = 5V VCC = 15V VCC = 3V IOL = 5mA TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 CURRENT LIMIT THRESHOLD VOLTAGE (mV) 1642a G20 27.5 27.0 26.5 26.0 25.5 25.0 24.5 VCC = 3V FB = 0V VCC = 15V VCC = 12V VCC = 5V FAULT and RESET Pull-Up Current (IOH) vs VCC FAULT and RESET VOL vs Temperature FAULT and RESET VOL vs Temperature Current Limit Threshold Voltage (Full Foldback) vs Temperature Current Limit Threshold Voltage (Nominal) vs Temperature TEMPERATURE (°C) –50 –25 0 25 50 75 100 125 CURRENT LIMIT THRESHOLD VOLTAGE (mV) 1642a G21 57.0 56.5 56.0 55.5 55.0 54.5 54.0 53.5 VCC = 3V FB = 1V VCC = 15V VCC = 5V VCC = 12V Reference O/P Impedance IREF (mA) 0 2.5 5 7.5 10 12.5 15 17.5 20 ∆VREF (mV) 1642a G37 –10 –12 –14 –16 –18 –20 –22 –4 2 VCC = 12V, 15V TA = 25°C VCC = 5V VCC = 3.3V

CRWBR (Pin 1): Overvoltage Crowbar Circuit Timer and Trigger. This pin controls an external overvoltage crowbar circuit. A capacitor from the pin to ground sets a 9ms/µF delay after an overvoltage occurs until an external SCR is triggered. See Applications Information. Ground the CRWBR pin if unused. BRK TMR (Pin 2): Circuit Breaker Timer. Connect a capacitor from BRK TMR to ground to set a 60ms/µF delay from the time the sense resistor current reaches its limit until the FET is shut off. FAULT output is then asserted and the FET remains off until the chip is reset. Ground BRK TMR to allow the part to remain in current limit indefinitely. RST TMR (Pin 3): Analog System/Reset Timer. A capaci- tor from this pin to ground sets a 0.6s/µF delay from the ON pin going high to the start of the GATE pin’s ramp. It also sets the delay from output voltage good, as sensed by the FB pin, to RESET going high. ON (Pin 4): ON Control Input. When ON is low the GATE pin is grounded and FAULT goes high. The GATE pin voltage starts ramping up one RST TMR timing cycle after ON goes high. Pulsing the ON pin low for at least 2µs resets the chip if it latches off after a sustained overvoltage or current limit. The threshold for a low to high transition is 1.34V with 110mV of hysteresis. A 21V zener clamp limits the voltage at this pin. The pin can be safely tied to V CC > 21V through a series resistor that limits the current below 1mA. RESET (Pin 5): Open Drain Reset Output. RESET is pulled low if the voltage at the FB pin is below its trip point. RESET goes high one RESET timing cycle after the FB voltage exceeds its trip point plus 3mV of hysteresis. RESET has a weak pull-up to one diode drop below V CC and an external resistor can pull the pin above V CC. A 21V zener clamp limits the voltage at this pin. The pin can be safely tied to V CC > 21V through a series resistor that limits the current below 1mA. FAULT (Pin 6): Open Drain Fault Output. FAULT is pulled low when the part turns off following a sustained overvolt- age or current limit. It goes high 2µs after the ON pin goes low. FAULT has a weak pull-up to one diode drop below VCC and an external resistor can pull the pin above VCC. A 21V zener clamp limits the voltage at this pin. The pin can be safely tied to VCC > 21V through a series resistor that limits the current below 1mA. FB (Pin 7): Output Voltage Monitor and Foldback Input. The FB comparator can be used with an external resistive divider to monitor the output supply voltage. When the FB voltage is lower than 1.22V the RESET pin is pulled low. RESET goes high one system timing cycle after the voltage at FB exceeds its threshold by 3mV of hysteresis. A low pass filter at the comparator’s output prevents negative voltage glitches from triggering a false reset. GND (Pin 8): Chip Ground.

OV (Pin 9): Overvoltage Input. When the voltage on OV exceeds its trip point the GATE pin is pulled low immedi- ately and the CRWBR timer starts. If OV remains above its trip point (minus 3mV of hysteresis) long enough for CRWBR to reach its trip point, then the part turns off until reset by pulsing the ON pin low. Otherwise, the GATE pin begins ramping up one RST TMR timing cycle after OV goes below its trip point. Ground the OV pin to disable overvoltage protection. COMPOUT (Pin 10): Uncommitted Comparator’s Open Drain Output. COMP + (Pin 11): Uncommitted Comparator’s Noninvert- ing Input. COMP– (Pin 12): Uncommitted Comparator’s Inverting Input. REF (Pin 13): Reference Voltage Output. The 1.22V ± 1% reference should be bypassed with a 0.1µF compensation capacitor. For V CC = 5V it can source 1mA. GATE (Pin 14): Gate Drive for the External N-Channel MOSFET. An internal charge pump provides at least 4.5V of gate drive and sources 25 µA. The pin requires an external series RC network to ground to compensate the current limit loop and to limit the ramp rate. A resistor of 100Ω is also recommended in series with the MOSFET gate to suppress high frequency oscillations. GATE is PI FU CTIO S UU U immediately pulled to ground when the overvoltage com- parator trips or the input supply is below the undervoltage lockout trip point. During current limit the GATE voltage is adjusted to maintain constant load current until the circuit breaker timer trips. At that point GATE is pulled to ground until the chip is reset. Clamp the GATE pin with a zener diode to ground if the supply is 8V or higher. For the 8V to 12V range use an 18V zener (1N4705), and for supplies exceeding 12V use a 20V zener (TOSHIBA 02DZ20Y). SENSE (Pin 15): Current Sense Input. To use the current limit place a sense resistor in the supply path between V CC and SENSE. When the drop across the resistor exceeds a threshold voltage, the GATE pin is adjusted to maintain a constant load current and the circuit breaker timer is started. A foldback feature reduces the current limit as the voltage at FB approaches ground. Short SENSE to V CC to disable the current limiting. VCC (Pin 16): Positive Supply Voltage. An internal under- voltage lockout circuit holds the GATE pin at ground until VCC exceeds 2.73V. If VCC exceeds 16.5V an internal shunt regulator protects the chip from V CC and SENSE pin voltages up to 33V. In this case the GATE pin voltage will usually be low but this is not guaranteed; use the OV pin to ensure that the pass device is off. The V CC pin also provides a high side connection to the SENSE resistor.

–7FB 1.22V 0.41V 1.22V 16VCC GATE CHARGE PUMP 25µA 23mV TO 53mV +9OV 1.22V +4ON 1.22V +VCC VCC 2.7V +11 12COMP– COMP+ RISING DELAY 15µs TO 100µs RISING DELAY 15µs TO 100µs RISING DELAY 2µs RISING DELAY 10µs CRWBR 45µA 1.5mA 1.22V BRK TMR 20µA 1.22V RST TMR 1642a BD 2µA

6 FAULT

10µA AT 5V VCC SENSE

5 RESET

10µA AT 5V VCC

13 REF

10 COMPOUT

21.5V 21V 21V 21V 21V 21V 21V BLOCK DIAGRA W

The uncommitted comparator has an open drain output. COMPOUT pins may be left floating. Figure 15. Recommended Layout for R1, R2 and R5 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. and GND pins short. Figure 15 shows an example layout.

© LINEAR TECHNOLOGY CORPORATION 1 999 LT/TP 0605 500 • PRINTED IN USA RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1421 Hot Swap Controller Two Supplies from 3V to 12V and –12V LTC4211 Hot Swap Controller with Multifunction Current Control Single Supply from 2.5V to 16.5V, MSOP Package LT4250 Negative Voltage Hot Swap Controller in SO-8 –48V Supplies, Active Current Limit LTC1643 PCI-Bus Hot Swap Controller 3.3V, 5V, ±12V Supplies for PCI Bus, Active Current Limit TYPICAL APPLICATIO U Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com 12V Hot Swap Circuit for InfiniBand Modules 1N4705 18V REF COMP – CRWBR RST TMR BRK TMR GND VCC SENSE GATE COMPOUT RESET FB FAULT ON OV COMP+ LTC1642A 13 12 1 3 2 8 16 15 14 100Ω 0.047µF 330Ω R12 84.5k 1%R6 127k 10.2k 1% R2 Q1 0.01µF R11 12.4k 0.1µF 0.01µF C1* 0.033µF 30k 0.033µF D1* 1N4148 10k 681k 100k DC/DC CONVERTER INPUT TO CONVERTER'S RUN/SS TO DC/DC RETURN 1642a TA02 VB_In VBxEn_L VB_Ret InfiniBand BACKPLANE InfiniBand MODULE LOCAL POWER ENABLE UV *INSTALL D1 FOR AUTOMATIC RESTART IF USING D1, INCREASE C1 START-UP DELAY IS 20ms TYPICAL CIRCUIT-BREAKER DELAY IS 1ms TYPICAL †FAIRCHILD (408) 822-2126 REWOPELUDOM2 R1 Q W52% 5,Ω510.02 †166SDF W05% 5,Ω700.00 †866SDF LONG SHORT LONG PACKAGE DESCRIPTIO U GN16 (SSOP) 0204 12 3 4 5 6 7 8 .229 – .244 (5.817 – 6.198) .150 – .157** (3.810 – 3.988) 16 15 14 13 .189 – .196* (4.801 – 4.978) 12 11 10 9 .016 – .050 (0.406 – 1.270) .015 ± .004 0° – 8° TYP.007 – .0098 (0.178 – 0.249) .0532 – .0688 (1.35 – 1.75) .008 – .012 (0.203 – 0.305) TYP .004 – .0098 (0.102 – 0.249) .0250 (0.635) BSC .009 (0.229) REF .254 MIN RECOMMENDED SOLDER PAD LAYOUT .150 – .165 .0250 BSC.0165 ± .0015 .045 ±.005 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE INCHES (MILLIMETERS) NOTE: 1. CONTROLLING DIMENSION: INCHES 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641)