LTC1647-1/ LTC1647-2/LTC1647-3 Dual Hot Swap Controllers FEATURES DESCRIPTION n The LTC(R)1647-1/LTC1647-2/LTC1647-3 are dual Hot SwapTM controllers that permit a board to be safely inserted and removed from a live backplane. n n n n n n Allows Safe Board Insertion and Removal from a Live Backplane Programmable Electronic Circuit Breaker FAULT Output Indication Programmable Supply Voltage Power-Up Rate High Side Drive for External MOSFET Switches Controls Supply Voltages from 2.7V to 16.5V Undervoltage Lockout APPLICATIONS n n n n Hot Board Insertion Electronic Circuit Breaker Portable Computer Device Bays Hot Plug Disk Drive L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Using external N-channel MOSFETs, the board supply voltages can be ramped up at a programmable rate. A high side switch driver controls the MOSFET gates for supply voltages ranging from 2.7V to 16.5V. A programmable electronic circuit breaker protects against overloads and shorts. The ON pins are used to control board power or clear a fault. The LTC1647-1 is a dual Hot Swap controller with a common VCC pin, separate ON pins and is available in an SO-8 package. The LTC1647-2 is similar to the LTC1647-1 but combines a fault status flag with automatic retry at the ON pins and is also available in the SO-8 package. The LTC1647-3 has individual VCC pins, ON pins and FAULT status pins for each channel and is available in a 16-lead narrow SSOP package. TYPICAL APPLICATION Dual Motherboard Resident Hot Swap Controller 20m 12V SUPPLY IRF7413 ON/OFF Sequence VOUT1 (2.5A) + CLOAD VON 5V/DIV 10 VCC ON1 ON1 ON2 ON2 GND SENSE 1 GATE 1 10nF VGATE 10V/DIV DDZ23* LTC1647-1 VOUT 5V/DIV SENSE 2 GATE 2 10 10ms/DIV DDZ23* 10nF 20m IRF7413 1647-1/2/3 TA01a VOUT2 (2.5A) + CLOAD *REQUIRED FOR VCC > 10V 1647-1/2/3 TA01 1647fa 1 LTC1647-1/ LTC1647-2/LTC1647-3 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltage (VCC) ................................................17V Input Voltage (SENSE) ................. - 0.3V to (VCC + 0.3V) Input Voltage (ON) .....................................- 0.3V to 17V Output Voltage (FAULT) ..............................- 0.3V to 17V Output Voltage (GATE) ...........Internally Limited (Note 3) Operating Temperature Range C-Grade ................................................... 0C to 70C I-Grade................................................. -40C to 85C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C PIN CONFIGURATION TOP VIEW TOP VIEW TOP VIEW VCC1 1 16 VCC2 ON1 2 15 SENSE1 VCC 1 8 SENSE1 VCC 1 8 SENSE1 FAULT1 3 14 SENSE2 ON1 2 7 SENSE2 ON1/FAULT1 2 7 SENSE2 ON2 4 13 GATE1 5 12 GATE2 ON2 3 6 GATE1 ON2/FAULT2 3 6 GATE1 FAULT2 GND 4 5 GATE2 GND 4 5 GATE2 NC 6 11 NC NC 7 10 NC GND 8 9 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, qJA = 130C/W S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, qJA = 130C/W NC GN PACKAGE 16-LEAD PLASTIC SSOP TJMAX = 150C, qJA = 130C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC1647-1CS8#PBF LTC1647-1CS8#TRPBF 16471 8-Lead (4mm 3mm) Plastic SO 0C to 70C LTC1647-1IS8#PBF LTC1647-1IS8#TRPBF 16471I 8-Lead (4mm 3mm) Plastic SO -40C to 85C 0C to 70C LTC1647-2CS8#PBF LTC1647-2CS8#TRPBF 16472 8-Lead (4mm 3mm) Plastic SO LTC1647-2IS8#PBF LTC1647-2IS8#TRPBF 16472I 8-Lead (4mm 3mm) Plastic SO -40C to 85C LTC1647-3CGN#PBF LTC1647-3CGN#TRPBF 16473 16-Lead Plastic SSOP 0C to 70C LTC1647-3IGN#PBF LTC1647-3IGN#TRPBF 16473I 16-Lead Plastic SSOP -40C to 85C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 1647fa 2 LTC1647-1/ LTC1647-2/LTC1647-3 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. SYMBOL PARAMETER VCC VCCX Supply Range CONDITIONS MIN Operating Range l TYP 2.7 MAX UNITS 16.5 V ICC VCC Supply Current (Note 4) ON1, ON2 = VCC1 = VCC2, ICC = ICC1 + ICC2 l 1.0 6 mA ICCX VCCX Supply Current (Note 5, LTC1647-3) ONX = VCCX, ICCX Individually Measured, VCC1 = 5V, VCC2 = 12V or VCC1 = 12V, VCC2 = 5V l 0.5 5 mA VLKO VCCX Undervoltage Lockout Coming Out of UVLO (Rising VCCX) l 2.45 2.60 VLKH VCCX Undervoltage Lockout Hysteresis VCB Circuit Breaker Trip Voltage VCB = VCCX - VSENSEX l 40 50 60 mV ICP GATEX Output Current ONX High, FAULTX High, VGATE = GND (Sourcing) ONX Low, FAULTX High, VGATE = VCC (Sinking) ONX High, FAULTX Low, VGATE = 15V (Sinking) l 6 10 50 50 14 A A mA VGATE External MOSFET Gate Drive (VGATE - VCC), VCC1 = VCC2 = 5V (VGATE - VCC), VCC1 = VCC2 = 12V l l 10 10 13 15 17 19 V V VONHI ONX Threshold High l 1.20 1.29 1.38 V ONX Threshold Low l 1.17 1.21 1.25 VONLO 2.30 210 VONHYST ONX Hysteresis 70 IIN ONX Input Current ON = GND or VCC l VOL FAULTX Output Low Voltage (LTC1647-2, LTC1647-3) IO = 1mA, VCC = 5V IO = 5mA, VCC = 5V l ILEAK FAULTX Output Leakage Current (LTC1647-3) No Fault, FAULTX = VCC = 5V 1 tFAULT Circuit Breaker Delay Time VCCX - VSENSEX = 0 to 100mV 0.3 1 V mV V mV 10 A 0.4 V V 10 A 0.8 s tRESET Circuit Breaker Reset Time ONX High to Low, to FAULTX High tON Turn-On Time ONX Low to High, to GATEX On 2 s tOFF Turn-Off Time ONX High to Low, to GATEX Off 1 s Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to ground unless otherwise specified. Note 3: An internal Zener on the GATE pins clamp the charge pump voltage to a typical maximum operating voltage of 28V. External overdrive l 50 100 s of the GATE pin beyond the internal Zener voltage may damage the device. The GATE capacitance must be < 0.15F at maximum VCC. If a lower GATE pin clamp voltage is desired, use an external Zener diode. Note 4: The total supply current ICC is measured with VCC1 and VCC2 connected internally (LTC1647-1, LTC1647-2) or externally (LTC1647-3). Note 5: The individual supply current ICCX is measured on the LTC1647-3. The lower of the two supplies, VCC1 and VCC2, will have its channel's current. The higher supply will carry the additional supply current of the charge pump and the bias generator beside its channel's current. 1647fa 3 LTC1647-1/ LTC1647-2/LTC1647-3 PIN TABLES LTC1647-1 Pinout PIN LTC1647-3 Pinout DESCRIPTION PIN DESCRIPTION PIN DESCRIPTION PIN DESCRIPTION 1 VCC 5 GATE2 1 VCC 9 NC 2 ON1 6 GATE1 2 ON1 10 NC 3 ON2 7 SENSE2 3 FAULT1 11 NC 4 GND 8 SENSE1 4 ON2 12 GATE2 5 FAULT2 13 GATE1 6 NC 14 SENSE2 7 NC 15 SENSE1 8 GND 16 VCC2 LTC1647-1 Does Not Have the FAULT Status Feature. LTC1647-2 Pinout PIN DESCRIPTION PIN DESCRIPTION 1 VCC 5 GATE2 2 ON1 and FAULT1 (Internally Tied Together) 6 GATE1 ON1 and FAULT2 (Internally Tied Together) 7 SENSE2 3 8 SENSE1 4 GND The ONX/FAULTX must be connected to a driver via a resistor if the autoretry feature is being used. TYPICAL PERFORMANCE CHARACTERISTICS ICC vs VCC ICC vs Temperature 6 TA = 25C ICC = ICC1 + ICC2 VCC = VCC1 = VCC2 = ON1 = ON2 5 5 5 ICC = ICC1 + ICC2 VCC = VCC1 = VCC2 = ON1 = ON2 TA = 25C 4 3 3 2 2 1 1 VCC = 15V ICC1 (mA) 4 ICC (mA) 4 ICC (mA) ICC1 vs VCC2 6 VCC = 12V VCC = 5V 0 2 4 6 8 10 12 VCC (V) 14 16 18 1647-1/2/3 G01 0 -75 -50 -25 3 VCC1 = 15V VCC1 = 12V 2 VCC1 = 5V 1 VCC1 = 3V VCC = 3V 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G02 0 0 2 4 6 8 10 12 14 16 18 20 VCC2 (V) 1647-1/2/3 G03 1647fa 4 LTC1647-1/ LTC1647-2/LTC1647-3 TYPICAL PERFORMANCE CHARACTERISTICS ICC2 vs VCC2 (VGATE - VCC) vs VCC 5 TA = 25C 25 16 VCC1 = 15V VCC1 = 12V 2 VCC1 = 3V 1 14 20 12 VGATE (V) 3 (VGATE - VCC) (V) 10 8 4 VCC1 = 5V 0 2 4 6 0 0 2 4 6 8 0 10 12 14 16 18 20 VCC (V) 1647-1/2/3 G04 (VGATE - VCC) vs Temperature VGATE vs Temperature 8 VGATE (V) VCC = 15V VCC = 3V 6 VCC = 5V VCC = 12V 20 15 VCC = 3V 10 4 5 VCC = VCC1 = VCC2 2 VCC = VCC1 = VCC2 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 6 0 VCC1 = 3V 20 VCC1 = 3V 10 TA = 25C (LTC1647-3) 5 0 2 4 6 8 10 12 14 16 18 20 VCC2 (V) 1647-1/2/3 G10 0 2 4 6 8 10 12 14 16 18 20 VCC2 (V) GATE Output Source Current vs Temperature 14 TA = 25C VCC = VCC1 =VCC2 13 GATE OUTPUT SOURCE CURRENT (A) VCC1 = 5V GATE OUTPUT SOURCE CURRENT (A) 30 TA = 25C (LTC1647-3) 1647-1/2/3 G09 14 VCC1 = 15V 12 11 10 9 8 7 6 VCC1 = 15V 8 GATE Output Source Current vs VCC 35 VGATE1 (V) VCC1 = 5V 10 1647-1/2/3 G08 VGATE1 vs VCC2 0 12 2 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G07 15 10 12 14 16 18 20 VCC (V) 14 4 VCC1 = 12V 8 16 12 25 6 VCC1 = 12V 18 25 0 -75 -50 -25 4 (VGATE1 - VCC1) vs Temperature VCC = 15V 30 14 10 2 20 VCC = 12V VCC = 5V 16 0 1647-1/2/3 G06 35 18 TA = 25C VCC = VCC1 = VCC2 1647-1/2/3 G05 20 (VGATE - VCC) (V) 5 TA = 25C VCC = VCC1 = VCC2 2 8 10 12 14 16 18 20 VCC2 (V) 15 10 6 (VGATE1 - VCC1) (V) ICC2 (mA) 30 18 4 0 VGATE vs VCC 20 0 2 4 6 8 10 12 14 16 18 20 VCC (V) 1647-1/2/3 G11 13 VCC = VCC1 = VCC2 = 5V 12 11 10 9 8 7 6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G12 1647fa 5 LTC1647-1/ LTC1647-2/LTC1647-3 TYPICAL PERFORMANCE CHARACTERISTICS GATE Output Sink Current vs Temperature GATE Output Sink Current vs VCC GATE OUTPUT SINK CURRENT (A) GATE OUTPUT SINK CURRENT (A) 80 70 60 50 40 30 20 10 0 60 55 TA = 25C 90 VCC = 5V 54 GATE FAST PULL-DOWN CURRENT (mA) 100 53 52 51 50 49 48 47 46 0 2 4 6 8 45 -75 -50 -25 10 12 14 16 18 20 VCC (V) 30 20 10 0 -75 -50 -25 58 56 54 52 50 48 46 44 42 40 0 25 50 75 100 125 150 TEMPERATURE (C) 0 2 4 6 8 58 56 54 2.2 2.1 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G19 10 12 14 16 18 20 VCC (V) VCC = 15V VCC = 12V VCC = 5V VCC = 3V 48 46 44 42 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G18 ON Threshold Voltage vs Temperature 1.35 VCC = 5V 1.30 ON THRESHOLD VOLTAGE (V) ON THRESHOLD VOLTAGE (V) FALLING EDGE 8 50 TA = 25C 2.3 6 40 -75 -50 -25 10 12 14 16 18 20 VCC (V) 1.35 2.4 4 52 ON Threshold Voltage vs VCC 2.6 RISING EDGE 2 1647-1/2/3 G17 Undervoltage Lockout Threshold vs Temperature 2.5 0 60 TA = 25C 1647-1/2/3 G16 UNDERVOLTAGE LOCKOUT THRESHOLD (V) 35 Circuit Breaker Trip Voltage vs Temperature CIRCUIT BREAKER TRIP VOLTAGE (mV) CIRCUIT BREAKER TRIP VOLTAGE (mV) GATE FAST PULL-DOWN CURRENT (mA) 40 40 1647-1/2/3 G15 60 50 45 Circuit Breaker Trip Voltage vs VCC 80 60 50 1647-1/2/3 G14 GATE Fast Pull-Down Current vs Temperature VCC = VCC1 = VCC2 = 5V TA = 25C 55 30 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G13 70 GATE Fast Pull-Down Current vs VCC HIGH 1.25 LOW 1.20 1.15 0 2 4 6 8 10 12 14 16 18 20 VCC (V) 1647-1/2/3 G20 1.30 HIGH 1.25 LOW 1.20 1.15 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G21 1647fa 6 LTC1647-1/ LTC1647-2/LTC1647-3 TYPICAL PERFORMANCE CHARACTERISTICS FAULT VOL vs VCC FAULT VOL vs Temperature 2.0 1.6 1.4 1.4 FAULT VOL (V) FAULT VOL (V) 1.6 1.2 IOL = 5mA 1.0 0.8 0.6 TA = 25C VCC = 5V 1.8 0.8 1.2 1.0 IOL = 5mA 0.8 0.4 0.2 0.4 IOL = 1mA 0.2 0 2 4 6 8 IOL = 1mA 0.2 0 -75 -50 -25 10 12 14 16 18 20 VCC (V) 0 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G22 VCC = 5V VCC = 12V 0.2 VCC = 15V 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G25 6 8 10 12 14 16 18 20 VCC (V) 60 TA = 25C CIRCUIT BREAKER RESET TIME (s) 0.4 4 Circuit Breaker Reset Time vs Temperature 70 CIRCUIT BREAKER RESET TIME (s) 1.0 VCC = 3V 2 1647-1/2/3 G24 Circuit Breaker Reset Time vs VCC 0.8 0 1647-1/2/3 G23 tFAULT vs Temperature TFAULT (s) 0.6 0.6 0.4 0.6 TFAULT (s) TA = 25C 1.8 0 tFAULT vs VCC 1.0 2.0 60 50 40 30 0 2 4 6 8 10 12 14 16 18 20 VCC (V) 1647-1/2/3 G26 58 56 VCC = 3V 54 52 50 48 VCC = 5V VCC = 12V 46 VCC = 15V 44 42 40 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1647-1/2/3 G27 1647fa 7 LTC1647-1/ LTC1647-2/LTC1647-3 PIN FUNCTIONS VCC1 (LTC1647-3): Channel 1 Positive Supply Input. The supply range for normal operation is 2.7V to 16.5V. The supply current, ICC1, is typically 1mA. Channel 1's undervoltage lockout (UVLO) circuit disables GATE 1 until the supply voltage at VCC1 is greater than VLKO (typically 2.45V). GATE 1 is held at ground potential until UVLO deactivates. If ON1 is high and VCC1 is above the UVLO threshold voltage, GATE 1 is pulled high by a 10A current source. If VCC1 falls below (VLKO - VLKH), GATE 1 is pulled immediately to ground. The internal reference and the common charge pump are powered from the higher of the two VCC inputs, VCC1 or VCC2. VCC2 (LTC1647-3): Channel 2 Positive Supply Input. See VCC1 for functional description. VCC: The Common Positive Supply Input for the LTC1647-1 and the LTC1647-2. VCC1 and VCC2 are internally connected together. GND: Chip Ground. ON1: Channel 1 ON Input. The threshold at the ON1 pin is set at 1.29V with 70mV hysteresis. If UVLO and the circuit breaker of channel 1 are inactive, a logic high at ON1 enables the 10A charge pump current source, pulling the GATE 1 pin above VCC1. If the ON1 pin is pulled low, the GATE 1 pin is pulled to ground by a 50A current sink. ON1 resets channel 1's electronic circuit breaker by pulling ON1 low for greater than one tRESET period (50s). A low-to-high transition at ON1 restarts a normal GATE 1 pull-up sequence. ON2: Channel 2 ON Input. See ON1 for functional description. FAULT1: Channel 1 Open-Drain Fault Status Output. FAULT1 pin pulls low after 0.3s (tFAULT) if the circuit breaker measures greater than 50mV across the sense resistor connected between VCC1 and SENSE 1. If FAULT1 pulls low, GATE 1 also pulls low. FAULT1 remains low until ON1 is pulled low for at least one tRESET period. FAULT2: Channel 2 Open-Drain Fault Status Output. See FAULT 1 for functional description. SENSE1: Channel 1 Circuit Breaker Current Sense Input. Load current is monitored by a sense resistor connected between VCC1 and SENSE 1. The circuit breaker trips if the voltage across the sense resistor exceeds 50mV (VCB). To disable the circuit breaker, connect SENSE 1 to VCC1. In order to obtain optimum performance, use Kelvin-sense connections between the VCC and SENSE pins to the current sense resistor. SENSE2: Channel 2 Circuit Breaker Current Sense Input. See SENSE 1 for functional description. GATE1: Channel 1 N-channel MOSFET Gate Drive Output. An internal charge pump guarantees at least 10V of gate drive from a 5V supply. Two Zener clamps are incorporated at the GATE 1 pin; one Zener clamps GATE 1 approximately 15V above VCC and the second Zener clamps GATE 1 appoximately 28V above GND. The rise time at GATE 1 is set by an external capacitor connected between GATE 1 and GND and an internal 10A current source provided by the charge pump. The fall time at GATE 1 is set by the 50A current sink if ON1 is pulled low. If the circuit breaker is tripped or the supply voltage hits the UVLO threshold, a 50mA current sink rapidly pulls GATE 1 low. An external 23V Zener from GATE1 to GND is required for supply voltages (VCC1) greater than 10V. GATE2: Channel 2 N-channel MOSFET Gate Drive Output. See GATE 1 for functional description. NC: No Connection. 1647fa 8 LTC1647-1/ LTC1647-2/LTC1647-3 BLOCK DIAGRAMS LTC1647-1 + - 50mV CHANNEL ONE + CP - SENSE1 8 1.21V 10A + 50s FILTER 6 GATE1 - ON1 2 50A 2.45V UVL VCC 1 GND 4 REFERENCE CHARGE PUMP 1.21V CP CHANNEL TWO (DUPLICATE OF CHANNEL ONE) SENSE2 7 5 GATE2 ON2 3 1647-1/2/3 BD1 LTC1647-2 + - 50mV CHANNEL ONE + CP - SENSE1 8 1.21V 10A + 50s FILTER ON1/FAULT1 2 6 GATE1 - 50A 2.45V UVL FAULT VCC 1 GND 4 SENSE2 7 REFERENCE 1.21V CHARGE PUMP CP CHANNEL TWO (DUPLICATE OF CHANNEL ONE) 5 GATE2 ON2/FAULT2 3 1647-1/2/3 BD2 1647fa 9 LTC1647-1/ LTC1647-2/LTC1647-3 BLOCK DIAGRAMS LTC1647-3 VCC1 1 + - 50mV CHANNEL ONE + CP - SENSE1 15 1.21V 10A + 50s FILTER ON1 2 FAULT1 3 GND 8 13 GATE1 - 50A 2.45V UVL FAULT REFERENCE CHARGE PUMP 1.21V CP VCC SELECTION VCC2 16 SENSE2 14 12 GATE2 CHANNEL TWO (DUPLICATE OF CHANNEL ONE) ON2 4 FAULT2 5 1647-1/2/3 BD3 APPLICATIONS INFORMATION VCC Selection Circuit Electronic Circuit Breaker The LTC1647-3 features separate supply inputs (VCC1 and VCC2) for each channel. The reference and charge pump circuit draw supply current from the higher of the two supplies. An internal VCC selection circuit detects and makes the power connection automatically. This allows a 3V channel to have standard MOSFET gate overdrive when the other channel is 5V. An internal Zener clamps GATE about 15V above VCC. Each channel of the LTC1647 features an electronic circuit breaker to protect against excessive load current and shortcircuits. Load current is monitored by sense resistor R1 as shown in Figure 1. The circuit breaker threshold, VCB, is 50mV and it exhibits a response time, tFAULT, of approximately 300ns. If the voltage between VCC and SENSE exceeds VCB for more than tFAULT, the circuit breaker trips and immediately pulls GATE low with a 50mA current sink. The MOSFET turns off and FAULT pulls low. The circuit breaker is cleared by pulling the ON pin low for a period of at least tRESET (50s). A timing diagram of these events is shown in Figure 2. If both supplies are connected together (internally for LTC1647-1 and LTC1647-2 or externally for LTC1647-3), the reference and charge pump circuit draw equal current from both pins. The value of the sense resistor R1 is given by: R1 = VCB/ITRIP() 1647fa 10 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION R1 0.01 Q1 IRF7413 VCC VOUT + R3 10k ON FAULT CLOAD R2 10 2 1 15 13 VCC SENSE GATE ON1 3 FAULT 8 C1 10nF *D1 DDZ23 LTC1647-3 GND *D1 REQUIRED FOR VCC > 10V 1647-1/2/3 F01 Figure 1. Supply Control Circuitry tFAULT tRESET VGATE VFAULT 1647-1/2/3 F02 Figure 2. Current Fault Timing Q1 IRF7413 R1 0.01 VCC VOUT + C3 10nF R3 1.5k CLOAD R2 10 C1 10nF VCC SENSE IPK = 7.5A IAV = 2.5A ITRIP = VCB/R1 = 5A tDELAY = 10s LTC1647 1647-1/2/3 F03 Figure 3. Filtering Current Ripple/Glitches Q1 VCC VOUT D1* D2 1N4148 Minimize the effects of ripple current by either filtering the VOUT line or adding an RC filter to the SENSE pin. A series inductance of 1H to 10H inserted between Q1 and CLOAD is adequate ripple current suppression in most cases. Alternatively, a filter, consisting of R3 and C3 (Figure 3), simply filters the ripple component from the SENSE pin at the expense of response time. The added delay is given by: tDELAY = - R3*C3*ln[1 - (VCB/R1 - IAV)/(IPK - IAV)] Power MOSFET Selection GATE R1 The circuit breaker trip voltage has a tolerance of 20%; combined with a 5% sense resistor, the total tolerance is 25%. Therefore, calculate R1 based on a trip current ITRIP of no less than 125% of the maximum operating current. Do not neglect the effect of ripple current, which adds to the maximum DC component of the load current. Ripple current may arise from any of several sources, but the worst offenders are switching supplies. A switching regulator on the load side will attempt to draw some ripple current from the backplane and this current passes through the sense resistor. Similarly, output ripple from a switching regulator supplying the backplane will flow through the sense resistor and into the load capacitor. VON VCC - VSENSE where VCB is the circuit breaker trip voltage (50mV) and ITRIP is the value of the load current at which the circuit breaker trips. Kelvin-sense layout techniques between the sense resistor and the VCC and SENSE pins are highly recommended for proper operation. D2 1N4148 D4* **D5 *D1, D4 USER SELECTED VOLTAGE CLAMP 1N4688 (5V) 1N4692 (7V): LOGIC-LEVEL MOSFET 1N4695 (9V) 1N4702 (15V): STANDARD-LEVEL MOSFET **D5 DDZ23 (23V) REQUIRED FOR VCC > 10V Figure 4. Optional Gate Clamp 1647-1/2/3 F04 Power MOSFETs are classified into two catagories: standard MOSFETs (RDS(ON) specified at VGS = 10V) and logic-level MOSFETs (RDS(ON) specified at VGS = 5V). The absolute maximum rating for VGS is typically 20V for standard MOSFETs. The maximum rating for logic-level MOSFETs is lower and ranges from 8V to 16V depending on the manufacturer and specific part number. Some logic-level MOSFETs have a 20V maximum VGS rating. The LTC1647 is primarily targeted for standard MOSFETs; low supply voltage applications should use logic-level MOSFETs. GATE overdrive as a function of VCC is illustrated in the Typical Performance Curves. If lower GATE overdrive is desired, connect a diode in series with a Zener between GATE and VCC or between GATE and VOUT as shown in Figure 4. For 1647fa 11 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION an input supply greater than 10V at VCC1 or VCC2, a 24V Zener is recommended between the corresponding GATE1 or GATE2 pin and GND as shown in Figures 1 and 4. The RDS(ON) of the external pass transistor must be low to make VDS a small percentage of VCC. At VCC = 3.3V, VDS + VCB = 0.1V yields 3% error at maximum load current. This restricts the choice of MOSFETs to very low RDS(ON). At higher VCC voltages, the RDS(ON) requirement can be relaxed. MOSFET package dissipation (PD and TJ) may restrict the value of RDS(ON). If the ON pin is connected to VCC, or is pulled high before VCC is first applied, GATE is held low until VCC rises above the undervoltage lockout threshold, VLKO (Figure 6). Once the threshold is exceeded, GATE ramps at a controlled rate of 10A/C1. When the power supply is disconnected, the body diode of Q1 holds VCC about 700mV below VOUT. The GATE voltage droops at a rate determined by VCC. If VCC drops below VLKO - VLKH , the LTC1647 enters UVLO and GATE pulls down to GND. VGATE VCC + VGATE Power Supply Ramping VOUT is controlled by placing MOSFET Q1 in the power path (Figure 1). R1 provides load current fault detection and R2 prevents MOSFET high frequency oscillation. By ramping the gate of the pass transistor at a controlled rate (dV/dt = 10A/C1), the transient surge current (I = CLOAD*dV/dt = 10A*CLOAD/C1) drawn from the main backplane is limited to a safe value when the board is inserted into the connector. When power is first applied to VCC , the GATE pin pulls low. A low-to-high transition at the ON pin initiates GATE rampup. The rising dV/dt of GATE is set by 10A/C1 (Figure 5), where C1 is the total external capacitance between GATE and GND. The ramp-up time for VOUT is equal to t = (VCC*C1)/10A. A high-to-low transition at the ON pin initiates a GATE ramp-down at a slope of - 50A/C1. This rate is usually adequate as the supply bypass capacitors take time to discharge through the load. VGATE VCC + VGATE VGATE DROOP DUE TO VCC RAMP-UP SLOPE = 10A/C1 FAST RAMP-DOWN AT UNDERVOLTAGE LOCKOUT VOUT VCC CLOAD DISCHARGES 0V VCC OUT OF UVLO VCC INTO UVLO VCC UNPLUGGED VLKO VLKO - VLKH 0V 1647-1/2/3 F06 Figure 6. Supply Turn-On/Off with VCC Q1 IRF7413 R1 0.01 VCC + VOUT CLOAD R2 10 ON (5V LOGIC) 1 R3 15k FAULT C3 0.1F VCC 2 4 ON/FAULT 8 C1 10nF 6 SENSE GATE LTC1647-2 GND RAMP-UP SLOPE = 10A/C1 RAMP-DOWN SLOPE = -50A/C1 VCC - VSENSE tRESET VOUT VCC VGATE CLOAD DISCHARGES 0V VCC 0V tDELAY VFAULT VON tRAMP 1647-1/2/3 F07 1647-1/2/3 F05 Figure 5. Supply Turn-On/Off with ON Figure 7. Autoretry Sequence 1647fa 12 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION Autoretry The LTC1647-2 and LTC1647-3 are designed to allow an automatic reset of the electronic circuit breaker after a fault condition occurs. This is accomplished by pulling the ON/FAULT (LTC1647-2) pin or the ON and FAULT pins tied together (LTC1647-3) high through a resistor, R3, as shown in Figure 7. An autoretry sequence begins if a fault occurs. If the circuit breaker trips, FAULT pulls the ON pin low. After a tRESET interval elapses, FAULT resets and R3 pulls the ON pin up. C3 delays GATE turn-on until the voltage at the ON pin exceeds VIH. The delay time is tDELAY = -R3*C3*ln[1-(VIH - VOL)/(VON - VOL)] GATE ramps up at 10A/C1 until Q1 conducts. If VOUT is still shorted to GND, the cycle repeats. The ramp interval is about tRAMP = VTH*C1/10A where VTH is the threshold voltage of the external MOSFET. Hot Circuit Insertion When circuit boards are inserted into a live backplane or a device bay, the supply bypass capacitors on the board can draw huge transient currents from the backplane or the device bay power bus as they charge up. The transient currents can damage the connector pins and glitch the system supply, causing other boards in the system to reset or malfunction. The LTC1647 is designed to turn two positive supplies on and off in a controlled manner, allowing boards to be safely inserted or removed from a live backplane or device bay. The LTC1647 can be located before or after the connector as shown in Figure 8. A staggered PCB connector can sequence pin conections when plugging and unplugging circuit boards. Alternatively, the control signal can be generated by processor control. capacitors slow the rate of rise of voltage and heavily damp any parasitic resonance of lead or trace inductance working against the supply bypass capacitors. The opposite is true for LTC1647 Hot Swap circuits on a daughterboard. In most cases, on the powered side of the MOSFET switch (VCC) there is no supply bypass capacitor present. An abrupt connection, produced by plugging a board into a backplane connector, results in a fast rising edge applied to the VCC line of the LTC1647. No bulk capacitance is present to slow the rate of rise and heavily damp the parasitic resonance. Instead, the fast edge shock excites a resonant circuit formed by a combination of wiring harness, backplane and circuit board parasitic inductances and MOSFET capacitance. In theory, the peak voltage should rise to 2X the input supply, but in practice the peak can reach 2.5X, owing to the effects of voltage dependent MOSFET capacitance. The absolute maximum VCC potential for the LTC1647 is 17V; any circuit with an input of more than 6.8V should be scrutinized for ringing. A well-bypassed backplane should not escape suspicion: circuit board trace inductances of as little as 10nH can produce sufficient ringing to overvoltage VCC . Check ringing with a fast storage oscilloscope (such as a LECROY 9314AL DSO) by attaching coax or a probe to VCC and GND, then repeatedly inserting the circuit board into the backplane. Figures 9a and 9b show typical results in a 12V application with different VCC lead lengths. The peak amplitude reaches 22V, breaking down the ESD protection diode in the process. Ringing There are two methods for eliminating ringing: clipping and snubbing. A transient voltage suppressor is an effective means of limiting peak voltage to a safe level. Figure 10 shows the effect of adding an ON Semiconductor, 1SMA12CAT3, on the waveform of Figure 9. Good engineering practice calls for bypassing the supply rail of any circuit. Bypass capacitors are often placed at the supply connection of every active device, in addition to one or more large value bulk bypass capacitors per supply rail. If power is connected abruptly, the bypass Figures 11a and 11b show the effects of snubbing with different RC networks. The capacitor value is chosen as 10X to 100X the MOSFET COSS under bias and R is selected for best damping--1 to 50 depending on the value of parasitic inductance. 1647fa 13 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION Supply Glitching VID Power Controller LTC1647 Hot Swap circuits on the backplane are generally used to provide power-up/down sequence at insertion/ removal as well as overload/short-circuit protection. If a short-circuit occurs at supply ramp-up, the circuit breaker trips. The partially enhanced MOSFET, Q1, is easily disconnected without any supply glitch. The two Hot Swap channels of the LTC1647 are ideally suited for VID power control in portable computers. Figure 13 shows an application using the LTC1647-2 on the system side of the device bay interface (1394 PHY and/or USB). The controller detects the presence of a peripheral in each device bay and controls the LTC1647-2. The timing waveform illustrates the following sequence of events: t1, rising out of undervoltage lockout with GATE 1 ramping up; t2, load current fault at R1; t3, circuit breaker resets with R5/C3 delay; t4/t5, controller gates off/on device supply with RC delay; t6, device enters undervoltage lockout. If a dead short occurs after a supply connection is made (Figure 12), the sense resistor R1 and the RDS(ON) of fully enhanced Q1 provide a low impedance path for nearly unlimited current flow. The LTC1647 discharges the GATE pin in a few microseconds, but during this discharge time current on the order of 150 amperes flows from the VCC power supply. This current spike glitches the power supply, causing VCC to dip (Figure 12a and 12b). On recovery from overload, some supplies may overshoot. Other devices attached to this supply may reset or malfunction and the overshoot may also damage some components. An inductor (1H to 10H) in series with Q1's source limits the short-circuit di/dt, thereby limiting the peak current and the supply glitch (Figure 12a and 12b). Additional power supply bypass capacitance also reduces the magnitude of the VCC glitch. If C6 is not connected in Figure 13, FAULT2 and ON2 will have similar waveforms. t7 initiates an ON sequence; t8, a load fault is detected at R7 with FAULT2 pulling low. If the controller wants to stretch the interval between retries, it can pull ON2 low at t9 ( t9 - t8 < 0.4*tRESET). At t10/t11, the controller initiates a new power-up/down sequence. 1647fa 14 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION BACKPLANE CONNECTOR STAGGERED PCB EDGE CONNECTOR Q1 R1 VCC VOUT + R4 CLOAD R5 R2 ON R3 Q2 2 3 FAULT 8 1 15 13 VCC SENSE GATE C1 ON FAULT LTC1647-3 GND 8a. HOT SWAP CONTROLLER ON MOTHERBOARD BACKPLANE CONNECTOR STAGGERED PCB EDGE CONNECTOR Q1 R1 VCC + R4 VOUT CLOAD R2 FAULT R3 2 3 8 1 15 13 VCC SENSE GATE C1 ON FAULT LTC1647-3 GND 8b. HOT SWAP CONTROLLER ON DAUGHTERBOARD 1647-1/2/3 F08 Figure 8. Staggered Pins Connection 1647fa 15 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION R1 0.01 8' Q1 IRF7413 + 12V + - POWER LEADS VOUT CLOAD R2 10 SCOPE PROBE C1 10nF *D1 DDZ23 LTC1647 1647-1/2/3 F09 * REQUIRED FOR VCC >10V 24V 4V/DIV 4V/DIV 24V 0V 0V 1s/DIV 1s/DIV 1647-1/2/3 F09a 9a. Undamped VCC Waveform (48" Leads) 1647-1/2/3 F09b 9b. Undamped VCC Waveform (8" Leads) Figure 9. Ring Experiment 1647fa 16 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION Q1 IRF7413 R1 0.01 VOUT R2 10 D1* C1 10nF 2V/DIV PCB EDGE CONNECTOR + - POWER LEADS 12V CLOAD *D2 DDZ23 LTC1647 0V 1647-1/2/3 F10 1s/DIV ON SEMICONDUCTOR * 1SMA12CAT3, REQUIRED FOR VCC > 10V 1647-1/2/3 F10a VCC Waveform Clamped by a Transient Suppressor Figure 10. Transient Suppressor Clamp POWER LEADS PCB EDGE CONNECTOR 12V + - BACKPLANE CONNECTOR R1 0.01 Q1 IRF7413 + R3 10 VOUT CLOAD R2 10 C1 0.1F C1 10nF *D1 DDZ232 LTC1647 1647-1/2/3 F11 *REQUIRED FOR VCC > 10V 12V 2V/DIV 12V 2V/DIV 12V BACKPLANE CONNECTOR + 0V 0V 1s/DIV 1s/DIV 1647-1/2/3 F11a 11a. VCC Waveform Damped by a Snubber (15, 6.8nF) 1647-1/2/3 F11b 11b. VCC Waveform Damped by a Snubber (10, 0.1F) Figure 11. Snubber "Fixes" 1647fa 17 LTC1647-1/ LTC1647-2/LTC1647-3 APPLICATIONS INFORMATION + - Q1 IRF7413 L1 2H R2 10 C2 100F C1 10nF *D1 DDZ23 LTC1647 *REQUIRED FOR VCC > 10V BOARD WITH POSSIBLE SHORT-CIRCUIT FAULT 12V + R1 0.01 BACKPLANE CONNECTOR SUPPLY GLITCH 1647-1/2/3 F12 Figure 12. Supply Glitch GATE OF MOSFET 5V/DIV GATE OF MOSFET 5V/DIV VCC 5V/DIV VCC 5V/DIV VCC SHORT-CIRCUIT SUPPLY CURRENT 10A/DIV VCC SHORT-CIRCUIT SUPPLY CURRENT 50A/DIV 5s/DIV 1647-1/2/3 F12a 12a. VCC Short-Circuit Supply Current Glitch without Any Limiting 5s/DIV 1647-1/2/3 F12b 12b. VCC Supply Glitch with 2H Series Inductor 1647fa 18 LTC1647-1/ LTC1647-2/LTC1647-3 R1 0.1 3.3V VID SUPPLY Q1 1/2 MMDF3N02HD R3** R2 10 ON1 CONNECTOR #1 APPLICATIONS INFORMATION DEVICE #1 + CLOAD* R4** 1394 PHY AND/OR USB PORT R5 10 8 C3 0.1F 1 2 3 4 R6 10 FAULT2 C1 10nF 6 SENSE1 GATE1 VCC ON1/FAULT1 CLOAD IS USER-SELECTED BASED ON THE DEVICE REQUIREMENTS ** R3, R4, R7 AND R8 ARE OPTIONAL DISCHARGE RESISTORS WHEN DEVICES ARE POWERED-OFF Q1, Q2: ON SEMICONDUCTOR * LTC1647-2 ON2/FAULT2 GND SENSE2 GATE2 7 C6 0.1F 5 C4 10nF R8 10 R7 0.1 Q2 1/2 MMDF3N02HD VID VLKO R9** CONNECTOR #2 FAULT1 DEVICE BAY CONTROLLER WITH 1394 PHY AND/OR USB ON2 DEVICE #2 + CLOAD* R10** 1394 PHY AND/OR USB PORT VLKO - VLKH VON1 t4 t5 FAULT 1 WAVEFORM SHOWN WITH C3 VFAULT1 VIH VIH VIL VR1 VGATE1 t1 t2 t3 t6 VON2 t9 t10 t11 FAULT 2 WAVEFORM SHOWN WITHOUT C6 VFAULT2 t7 VR7 t8 VGATE2 1647-1/2/3 F13 Figure 13. VID Power Controller with Fault Status and Retry Sequence 1647fa 19 LTC1647-1/ LTC1647-2/LTC1647-3 PACKAGE DESCRIPTION GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 - .196* (4.801 - 4.978) .045 .005 .009 (0.229) REF 16 15 14 13 12 11 10 9 .254 MIN .150 - .165 .229 - .244 (5.817 - 6.198) .0165 .0015 .150 - .157** (3.810 - 3.988) .0250 BSC RECOMMENDED SOLDER PAD LAYOUT 1 .015 .004 s 45 (0.38 0.10) .007 - .0098 (0.178 - 0.249) 4 2 3 5 6 .0532 - .0688 (1.35 - 1.75) 7 8 .004 - .0098 (0.102 - 0.249) 0 - 8 TYP .016 - .050 (0.406 - 1.270) .0250 (0.635) BSC .008 - .012 (0.203 - 0.305) TYP NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) GN16 (SSOP) 0204 *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 3. DRAWING NOT TO SCALE S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 - .197 (4.801 - 5.004) NOTE 3 .045 .005 .050 BSC 8 .245 MIN 7 6 5 .160 .005 .150 - .157 (3.810 - 3.988) NOTE 3 .228 - .244 (5.791 - 6.197) .030 .005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 - .020 s 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP .016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN .053 - .069 (1.346 - 1.752) .014 - .019 (0.355 - 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 2 3 4 .004 - .010 (0.101 - 0.254) .050 (1.270) BSC SO8 0303 1647fa 20 LTC1647-1/ LTC1647-2/LTC1647-3 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 10/10 Replaced Typical Application circuit 1 Updated Order Information section 2 Revised GATE1 description in Pin Functions section Revised Figures 1, 4, 6, 7, 8, 9, 10, 11 and 12 in Applications Information section 8 11, 12, 15, to 18 Updated references to Figure 12a and 12b in Applications Information section 14 Revised Figure 14 in Typical Applications and updated Related Parts list 20 1647fa 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 21 LTC1647-1/ LTC1647-2/LTC1647-3 TYPICAL APPLICATION Hot Swapping Two Supplies Two separate supplies can be independently controlled by using the LTC1647-3. In some applications, sequencing between the two power supplies is a requirement. For example, it may be necessary to ramp-up one supply first before allowing the second supply to power-up, as well as requiring that this same supply ramp-down last on power-down. Figure 14's circuit illustrates how to program the delays between the two pass transistors using the Q1 IRF7413 R1 0.01 5V SUPPLY + R3 100 R4 4.7k ON1 ON2 CONNECTOR FAULT 2 R5 10k R6 10k 3 4 5 8 GND ON1 and ON2 pins (time events t1 to t4). t5 and t7 show both channels being switched on simultaneously where sequencing is not crucial. Some applications require that both channels be gated off if a fault occurs in one channel. This is accomplished in Figure 14 by using a crisscross FAULT-to-SENSE arrangement of R3/R4 and R7/R8. t6 and t9 illustrate the circuit's operation. VOUT1 (5A) CLOAD 1 15 13 VCC1 SENSE1 GATE1 VR1 t6 R2 10 VR10 C1 10nF t9 VON1 t2 ON1 t3 VON2 FAULT1 t1 t4 t5 t7 t8 LTC1647-3 ON2 VOUT1 FAULT2 GND R7 12k VCC2 SENSE2 GATE2 14 12 16 R8 100 VOUT2 1647-1/2/3 F14 C3 10nF R9 10 R10 0.02 12V SUPPLY Q2 IRF7413 + *D1 DDZ23 VOUT2 (2.5A) CLOAD *REQUIRED FOR VCC > 10V Figure 14. Hot Swapping Two Supplies RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1421 2-Channel Hot Swap Controller 24-Pin, Operates from 3V to 12V and Supports -12V LTC1422 Hot Swap Controller in SO-8 System Reset Output with Programmable Delay LT1640AL/LT1640AH Negative Voltage Hot Swap Controller in SO-8 Operates from -10V to -80V LT1641 High Voltage Hot Swap Controller in SO-8 Operates from 9V to 80V LT1642 Fault Protected Hot Swap Controller Operates Up to 16.5V, Protected to 33V LTC1643L/LTC1643H PCI-Bus Hot Swap Controller 3.3V, 5V and 12V in Narrow 16-Pin SSOP LT1645 2-Channel Hot Swap Controller Operates from 1.2V to 12V, Power Sequencing 1647fa 22 Linear Technology Corporation LT 1010 REV A * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com " LINEAR TECHNOLOGY CORPORATION 1999