DESCRIPTIO APPLICATIO S TYPICAL APPLICATIO. LT1640AL/LT1640AH Negative Voltage Hot Swap Controller FEATURES

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1 LT60AL/LT60AH Negative oltage Hot Swap Controller FEATURES Allows Safe Board Insertion and Removal from a Live Backplane Operates from 0 to 0 Programmable Inrush Current Allows 50mA of Reverse Drain Pin Current Programmable Electronic Circuit Breaker Programmable Overvoltage Protection Programmable Undervoltage Lockout Power Good Control Output APPLICATIO S U Central Office Switching Distributed Power Systems Negative Power Supply Control DESCRIPTIO U The LT 60AL/LT60AH are -pin, negative voltage Hot Swap TM controllers that allow a board to be safely inserted and removed from a live backplane. Inrush current is limited to a programmable value by controlling the gate voltage of an external N-channel pass transistor. The pass transistor is turned off if the input voltage is less than the programmable undervoltage threshold or greater than the overvoltage threshold. A programmable electronic circuit breaker protects the system against shorts. The (LT60AL) or (LT60AH) signal can be used to directly enable a power module. The LT60AL is designed for modules with a low enable input and the LT60AH for modules with a high enable input. The LT60AL/LT60AH are available in -pin PDIP and SO packages., LTC and LT are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO U Input Inrush Current U = = R 56k 9.09k 0k U R 0.0Ω DIODES INC. SMAT0A THESE COMPONENTS ARE APPLICATION SPECIFIC AND MUST BE SELECTED BASED UPON OPERATING CONDITIONS AND DESIRED PERFORMANCE. SEE APPLICATIONS INFORMATION. DD LT60AL 5 6 C 50nF 5 R 0Ω R k C.nF Q IRF50 ON/OFF 9 IN OUT 5 C C C5 0.µF 00µF TRIM 00µF IN OUT LUCENT JW050A-E 60A TA0 CONTACT BOUNCE 60A F0b

2 LT60AL/LT60AH ABSOLUTE MAXIMUM RATINGS W W W Supply oltage ( DD ) to, Pins to Pin... to, Pins to 0 U, Pins to 60 Maximum Junction Temperature... 5 C U (Note ), All oltages Referred to Operating Temperature Range LT60ALC/LT60AHC... 0 C to 0 C LT60ALI/LT60AHI... 0 C to 5 C Storage Temperature Range C to 50 C Lead Temperature (Soldering, 0 sec) C PACKAGE/ORDER I FOR U N PACKAGE -LEAD PDIP TOP IEW 6 5 DD S PACKAGE -LEAD PLASTIC SO T JMAX = 5 C, θ JA = 0 C/W (N) T JMAX = 5 C, θ JA = 50 C/W (S) W U ATIO U ORDER PART NUMBER LT60ALCN LT60ALCS LT60ALIN LT60ALIS S PART MARKING 60AL 60ALI U N PACKAGE -LEAD PDIP TOP IEW 6 5 DD S PACKAGE -LEAD PLASTIC SO T JMAX = 5 C, θ JA = 0 C/W (N) T JMAX = 5 C, θ JA = 50 C/W (S) ORDER PART NUMBER LT60AHCN LT60AHCS LT60AHIN LT60AHIS S PART MARKING 60AH 60AHI Consult factory for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = 5 C. (Note ), DD =, = 0 unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS DC DD Supply Operating Range 0 0 I DD Supply Current U =, =, =. 5 ma CB Circuit Breaker Trip oltage CB = ( ) m I PU Pin Pull-Up Current Gate Drive On, = µa I PD Pin Pull-Down Current Any Fault Condition 50 0 ma I Pin Current = 50m 0 µa External Gate Drive ( ), 5 DD ( ), 0 DD < UH U Pin High Threshold oltage U Low to High Transition... UL U Pin Low Threshold oltage U High to Low Transition.9.. UHY U Pin Hysteresis 0 m I INU U Pin Input Current U = µa H Pin High Threshold oltage Low to High Transition.9.. L Pin Low Threshold oltage High to Low Transition HY Pin Hysteresis 0 m I IN Pin Input Current = µa

3 ELECTRICAL CHARACTERISTICS LT60AL/LT60AH The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = 5 C. (Note ), DD =, = 0 unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS PG Power Good Threshold, High to Low Transition...0 PGHY Power Good Threshold Hysteresis 0. I Drain Input Bias Current = µa OL Output Low oltage (LT60AL), ( ) < PG I OUT = ma I OUT = 5mA.50.0 Output Low oltage (LT60AH), = 5 ( ) I OUT = ma I OH Output Leakage (LT60AL), =, µa = 0 R OUT Power Good Output Impedance (LT60AH), ( ) < PG 6.5 kω ( to ) AC t PHL High to Low Figures,. µs t PHLU U Low to Low Figures,.5 µs t PLH Low to High Figures, 5.5 µs t PLHU U High to High Figures, 6.5 µs t PHL High to Gate Low Figures, µs t PHLPG Low to Low (LT60AL) Figures, µs Low to ( ) High (LT60AH) Figures, µs t PLHPG High to High (LT60AL) Figures, µs High to ( ) Low (LT60AH) Figures, µs Note : Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note : All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to unless otherwise specified. TYPICAL PERFOR A CE CHARACTERISTICS UW SUPPLY CURRENT (ma) Supply Current vs Supply oltage. TA = 5 C SUPPLY CURRENT (ma) Supply Current vs Temperature.6 DD = OLTAGE () Gate oltage vs Supply oltage T A = 5 C SUPPLY OLTAGE () TEMPERATURE ( C) SUPPLY OLTAGE () 60A G0 60A G0 60A G0

4 LT60AL/LT60AH TYPICAL PERFOR A CE CHARACTERISTICS UW OLTAGE () Gate oltage vs Temperature DD = TRIP OLTAGE (m) Circuit Breaker Trip oltage vs Temperature PULL-UP CURRENT (µa) 6 5 Gate Pull-Up Current vs Temperature = TEMPERATURE ( C) TEMPERATURE ( C) TEMPERATURE ( C) 60A G0 60A G05 60A G06 55 Gate Pull-Down Current vs Temperature = 0.5 Output Low oltage vs Temperature (LT60AL) I OUT = ma Output Impedance vs Temperature (LT60AH) >. PULL-DOWN CURRENT (ma) OUTPUT LOW OLTAGE () OUTPUT IMPEDANCE (kω) TEMPERATURE ( C) TEMPERATURE ( C) TEMPERATURE ( C) 00 60A G0 60A G0 60A G09 PI FU CTIO S U U U / (Pin ): Power Good Output Pin. This pin will toggle when is within PG of. This pin can be connected directly to the enable pin of a power module. When the pin of the LT60AL is above by more than PG, the pin will be high impedance, allowing the pull-up current of the module s enable pin to pull the pin high and turn the module off. When drops below PG, the pin sinks current to, pulling the enable pin low and turning on the module. When the pin of the LT60AH is above by more than PG, the pin will sink current to the pin which pulls the module s enable pin low, forcing it off. When drops below PG, the sink current is turned off and a 6.5k resistor is connected between and, allowing the module s pullup current to pull the enable pin high and turn on the module.

5 LT60AL/LT60AH PIN FUNCTIONS U U U (Pin ): Analog Overvoltage Input. When is pulled above the. low-to-high threshold, an overvoltage condition is detected and the pin will be immediately pulled low. The pin will remain low until drops below the.0 high-to-low threshold. U (Pin ): Analog Undervoltage Input. When U is pulled below the. high to low threshold, an undervoltage condition is detected and the pin will be immediately pulled low. The pin will remain low until U rises above the. low-to-high threshold. The U pin is also used to reset the electronic circuit breaker. If the U pin is cycled low and high following the trip of the circuit breaker, the circuit breaker is reset and a normal power-up sequence will occur. (Pin ): Negative Supply oltage Input. Connect to the lower potential of the power supply. (Pin 5): Circuit Breaker Sense Pin. With a sense resistor placed in the supply path between and, the circuit breaker will trip when the voltage across the resistor exceeds 50m. Noise spikes of less than µs are filtered out and will not trip the circuit breaker. If the circuit breaker trip current is set to twice the normal operating current, only 5m is dropped across the sense resistor during normal operation. To disable the circuit breaker, and can be shorted together. (Pin 6): Gate Drive Output for the External N-Channel. The pin will go high when the following start-up conditions are met: the U pin is high, the pin is low and ( ) < 50m. The pin is pulled high by a 5µA current source and pulled low with a 50mA current source. (Pin ): Analog Drain Sense Input. Connect this pin to the drain of the external N-channel and the pin of the power module. When the pin is below PG, the or pin will toggle. In some conditions, the pin is pulled below. The part is not damaged if the reverse pin current is limited to 50mA. DD (Pin ): Positive Supply oltage Input. Connect this pin to the higher potential of the power supply inputs and the pin of the power module. The input supply voltage ranges from 0 to 0. BLOCK DIAGRA W DD U REF CC AND REFERENCE GENERATOR CC REF OUTPUT DRIE / 50m LOGIC AND DRIE PG 60A BD 5

6 LT60AL/LT60AH TEST CIRCUIT 5 R 5k / DD LT60AL/LT60AH U U 60A F0 Figure. Test Circuit TIMING DIAGRAMS U W W..0 U t PHL t PLH t PHLU t PLHU 60A F0 60A F0 Figure. to Timing Figure. U to Timing 50m.. t PHL t PLHPG t PHLPG 60A F0 Figure. to Timing.. 0 t PLHPG t PHLPG = 0 60A F05 Figure 5. to / Timing 6

7 LT60AL/LT60AH APPLICATIO S I FOR ATIO U W U U Hot Circuit Insertion When circuit boards are inserted into a live backplane, the bypass capacitors at the input of the board s power module or switching power supply can draw huge transient currents as they charge up. The transient currents can cause permanent damage to the board s components and cause glitches on the system power supply. The LT60A is designed to turn on a board s supply voltage in a controlled manner, allowing the board to be safely inserted or removed from a live backplane. The chip also provides undervoltage, overvoltage and overcurrent protection while keeping the power module off until its input voltage is stable and within tolerance. Power Supply Ramping The input to the power module on a board is controlled by placing an external N-channel pass transistor (Q) in the power path (Figure 6a, all waveforms are with respect to the pin of the LT60A). R provides current fault detection and R prevents high frequency oscillations. Resistors R, and provide undervoltage and overvoltage sensing. By ramping the gate of Q up at a slow rate, the surge current charging load capacitors C and C can be limited to a safe value when the board makes connection. Resistor R and capacitor C act as a feedback network to accurately control the inrush current. The inrush current can be calculated with the following equation: I INRUSH = (5µA C L )/C where C L is the total load capacitance equal to C C module input capacitance. U = = R 56k 9.09k 0k U DD LT60AH 5 6 C 0.µF C 00µF ICOR I-JD-CY IN OUT IN IN OUT 5 C5 00µF 6 DIODES INC. SMAT0A R 0.0Ω C 50nF 5 R 0Ω Q IRF50 R k C.nF 60A F06a Figure 6a. Inrush Control Circuitry

8 LT60AL/LT60AH APPLICATIO S I FOR ATIO Capacitor C and resistor R prevent Q from momentarily turning on when the power pins first make contact. Without C and R, capacitor C would pull the gate of Q up to a voltage roughly equal to C/C GS (Q) before the LT60A could power up and actively pull the gate low. By placing capacitor C in parallel with the gate capacitance of Q and isolating them from C using resistor R, the problem is solved. The value of C should be: INMAX TH TH U W U U C C ( GD) where TH is the MOSFET s minimum gate threshold and INMAX is the maximum operating input voltage. R s value is not critical and is given by ( INMAX )/ 5mA. The waveforms are shown in Figure 6b. When the power pins make contact, they bounce several times. While the contacts are bouncing, the LT60A senses an undervoltage condition and the is immediately pulled low when the power pins are disconnected. Once the power pins stop bouncing, the pin starts to ramp up. When Q turns on, the voltage is held constant by the feedback network of R and C. When the voltage has finished ramping, the pin then ramps to its final value. CONTACT BOUNCE 60A F0b Figure 6b. Inrush Control Waveforms

9 LT60AL/LT60AH APPLICATIO S I FOR ATIO U W U U Electronic Circuit Breaker The LT60A features an electronic circuit breaker function that protects against short circuits or excessive supply currents. By placing a sense resistor between the and pin, the circuit breaker will be tripped whenever the voltage across the sense resistor is greater than 50m for more than µs as shown in Figure. Note that the circuit breaker threshold should be set sufficiently high to account for the sum of the load current and the inrush current. If the load current can be controlled by the / pin (as in Figure 6a), the threshold can be set lower, since it will never need to accommodate inrush current and load current simultaneously. When the circuit breaker trips, the pin is immediately pulled to and the external N-channel turns off. The pin will remain low until the circuit breaker is reset by pulling U low, then high or cycling power to the part. If more than µs deglitching time is needed to reject current noise, an external resistor and capacitor can be added to the sense circuit as shown in Figure. R and C act as a lowpass filter that will slow down the pin voltage from rising too fast. Since the pin will source current, typically 0µA, there will be a voltage drop on R. This voltage will be counted into the circuit breaker trip voltage just as the voltage across the sense resistor. A small resistor is recommended for R. A 00Ω for R will cause a m error. The following equation can be used to estimate the delay time at the pin: t t O t= R C In () ( ) ( t ) i Where (t) is the circuit breaker trip voltage, typically 50m. (t O ) is the voltage drop across the sense resistor before the short or overcurrent condition occurs. i is the voltage across the sense resistor when the short current or overcurrent is applied on it. Example: A system has a A current load and a 0.0Ω sense resistor is used. An extended delay circuit needs to be designed for a 50µs delay time after the load jumps to 5A. In this case: (t) = 50m (t O ) = 0m i = 5A 0.0Ω = 00m If we choose R = 00Ω, we will get C = µf. O U = = R 56k 9.09k 0k U C 5 DD LT60AL 6 C L 00µF 60A F0 DIODES INC. SMAT0A R 0.0Ω R C 50nF 5 Q IRF50 R R 0Ω k C.nF 60A F0 Figure. Short-Circuit Protection Waveforms Figure. Extending the Short-Circuit Protection Delay 9

10 LT60AL/LT60AH APPLICATIO S I FOR ATIO U W U U Under some conditions, a short circuit at the output can cause the input supply to dip below the U threshold, resetting the circuit breaker immediately. The LT60A then cycles on and off repeatedly until the short is removed. This can be minimized by adding a deglitching delay to the U pin with a capacitor from U to. This capacitor forms an RC time constant with the resistors at U, allowing the input supply to recover before the U pin resets the circuit breaker. A circuit that automatically resets the circuit breaker after a current fault is shown in Figure 9. Transistors Q and Q along with R, R, C and D form a programmable one-shot circuit. Before a short occurs, the pin is pulled high and Q is turned on, pulling node to. Resistor R turns off Q. When a short occurs, the pin is pulled low and Q turns off. Node starts to charge C and Q turns on, pulling the U pin low and resetting the circuit breaker. As soon as C is fully charged, R turns off Q, U goes high and the starts to ramp up. Q turns back on and quickly pulls node back to. Diode D clamps node one diode drop below. The duty cycle is set to 0% to prevent Q from overheating. D N DIODES INC. SMAT0A C µf Q N R M Q ZN0 R 50k R 56k 9.09k 0k U R 0.0Ω DD LT60AL 5 6 C 50nF 5 R 0Ω Q IRF50 R k C.nF C 00µF 60A F09a 60A F09b 0 Figure 9. Automatic Restart After Current Fault

11 LT60AL/LT60AH APPLICATIO S I FOR ATIO U W U U Undervoltage and Overvoltage Detection The U (Pin ) and (Pin ) pins can be used to detect undervoltage and overvoltage conditions at the power supply input. The U and pins are internally connected to analog comparators with 0m of hysteresis. When the U pin falls below its threshold or the pin rises above its threshold, the pin is immediately pulled low. The pin will be held low until U is high and is low. The undervoltage and overvoltage trip voltages can be programmed using a three resistor divider as shown in Figure 0a. With R = 56k, = 9.09k and = 0k, the undervoltage threshold is set to and the overvoltage threshold is set to. The resistor divider will also amplify the 0m hysteresis at the U pin and pin to 0.6 and. at the input, respectively. More hysteresis can be added to the U threshold by connecting resistor R between the U pin and the pin as shown in Figure 0b. R U =.( ) R =.( ) R U DD LT60AL LT60AH 60A F0a Figure 0a. Undervoltage and Overvoltage Sensing U =.6 U = = R 506k.k R 56k R 6.9k R.6M DD U LT60AL/LT60AH 5 6 DIODES INC. SMAT0A R 0.0Ω C 50nF 5 0Ω Q IRF50 60A F0b Figure 0b. Programmable Hysteresis for Undervoltage Detection

12 LT60AL/LT60AH APPLICATIO S I FOR ATIO The new threshold voltage when the input moves from low to high is: U, LH = UH R R R R R R R R where UH is typically.. The new threshold voltage when the input moves from high to low is: = R R R R R R R R R R U, HL UL where UL is typically.. The new hysteresis value will be: = U W U U R R R R R R R R HYS UHY R R With R = 56k, R = 6.9k and R =.6M, =.5 and UHY = 0m, the undervoltage threshold will be (from low to high) and.6 (from high to low). The hysteresis is 5.. A separate resistor divider should be used to set the overvoltage threshold given by: = H R With R = 506k, =.k and H =., the overvoltage threshold will be. / Output The / output can be used to directly enable a power module when the input voltage to the module is within tolerance. The LT60AL has a output for modules with an active low enable input, and the LT60AH has a output for modules with an active high enable input. When the voltage of the LT60AH is high with respect to (Figure ), the internal transistor Q is turned off and R and Q clamp the pin one diode drop ( 0.) above the pin. Transistor Q sinks the module s pull-up current and the module turns off. When the voltage drops below PG, Q will turn on, shorting the bottom of R to and turning Q off. The pull-up current in the module then flows through R, pulling the pin high and enabling the module. R LT60AH U PG DD R 6.5k Q Q C ACTIE HIGH ENABLE MODULE IN OUT ON/OFF IN OUT 5 6 C R R C DIODES INC. SMAT0A R Q 60A F Figure. Active High Enable Module

13 LT60AL/LT60AH APPLICATIO S I FOR ATIO U W U U When the voltage of the LT60AL is high with respect to, the internal pull-down transistor Q is off and the pin is in a high impedance state (Figure ). The pin will be pulled high by the module s internal pull-up current source, turning the module off. When the voltage drops below PG, Q will turn on and the pin will pull low, enabling the module. The signal can also be used to turn on an LED or optoisolator to indicate that the power is good as shown in Figure. Gate Pin oltage Regulation When the supply voltage to the chip is more than 5.5, the pin voltage is regulated at.5 above. If the supply voltage is less than 5.5, the voltage will be about below the supply voltage. At the minimum 0 supply voltage, the gate voltage is guaranteed to be greater than 6. The gate voltage will be no greater than for supply voltages up to 0. Drain Pin Protection A unique feature of the LT60A is the ruggedness of the pin. The is designed to withstand negative voltages (with respect to ) without requiring an external diode. A short circuit on the backplane pulls up the pin, but due to the storage capacitor C (Figure ), the pin is held more negative than the pin. The body diode of Q, plus the I R drop across R (if R is small), holds the pin to less than.5 below. A.5 reverse voltage gives rise to a 50mA reverse drain current, which is within the design capability of the LT60A. A design with R larger than 0.Ω may require a resistor in series with the pin to not exceed the 50mA drain current maximum. ACTIE LOW ENABLE MODULE IN OUT R LT60AL U PG DD Q C ON/OFF IN OUT 5 6 C R R C DIODES INC. SMAT0A R Q 60A F Figure. Active Low Enable Module

14 LT60AL/LT60AH APPLICATIO S I FOR ATIO U W U U R 56k 9.09k U DD LT60AL R 5k N5 C 00µF 0k 5 6 DIODES INC. SMAT0A R 0.0Ω C 50nF 5 R 0Ω Q IRF50 R k C.nF 60A F Figure. Using to Drive an Optoisolator PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. N Package -Lead PDIP (Narrow 0.00) (LTC DWG # ) 0.00 (0.60) MAX ± 0.05 (6. ± 0.) (.60.55) (..65) 0.0 ± (.0 ± 0.) (0.9 0.) ( ) (.65) TYP 0.00 (.5) BSC THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.00 INCH (0.5mm) 0.5 (.5) MIN 0.0 ± 0.00 (0.5 ± 0.06) 0.00 (0.50) MIN N 09

15 LT60AL/LT60AH PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. S Package -Lead Plastic Small Outline (Narrow 0.50) (LTC DWG # ) ( ) ( ) (.0.9) ( ) ( ) 5 0 TYP (.6.5) ( ) (0.06.0) DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.5mm) PER SIDE DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.00" (0.5mm) PER SIDE ( ) TYP (.0) BSC SO 9 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. 5

16 LT60AL/LT60AH TYPICAL APPLICATION Using an EMI Filter Module Many applications place an EMI filter module in the power path to prevent switching noise of the module from being injected back onto the power supply. A typical application U using the Lucent FLTR0 filter module is shown in Figure. When using a filter, an optoisolator is required to prevent common mode transients from destroying the and ON/OFF pins. R 5k R 56k DD U 9.09k LT60AL 0k 5 R 0.0Ω DIODES INC. SMAT0A 6 C.nF C 50nF 5 R k R 0Ω Q IRF50 C 0.µF IN IN N5 OUT LUCENT FLTR0 CASE OUT C 0.µF C5 00µF C6 0.µF LUCENT JW050A-E IN ON/OFF OUT TRIM 9 6 IN OUT 5 CASE 60A F 5 C 00µF 6 Figure. Typical Application Using a Filter Module RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC Dual Channel, Hot Swap Controller Operates from to LTC Hot Swap Controller in SO- System Reset Output with Programmable Delay, to LT6 Positive Hot Swap Controller in SO- Foldback Analog Current Limit LTC6 Fault Protected Hot Swap Controller Operates Up to 6.5, Protected to LTC6 PCI Hot Swap Controller., 5,, Supplies for PCI Bus LTC65 Dual Hot Swap Controller Operates from. to, Power Sequencing LTC66 CompactPCI TM Hot Swap Controller., 5 Supplies, Precharge, Local PCI Reset Logic LTC6 Dual Hot Swap Controller Dual ON Pins for Supplies from to 5 CompactPCI is a trademark of the PCI Industrial Computer Manufacturers Group 6 Linear Technology Corporation 60 McCarthy Blvd., Milpitas, CA (0) -900 FAX: (0) alahf LT/TP 050 K PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 00

TYPICAL APPLICATIO. LT1641-1/LT Positive High Voltage Hot Swap Controllers DESCRIPTIO FEATURES APPLICATIO S

TYPICAL APPLICATIO. LT1641-1/LT Positive High Voltage Hot Swap Controllers DESCRIPTIO FEATURES APPLICATIO S Positive High Voltage Hot Swap Controllers FEATURES Allows Safe Board Insertion and Removal from a Live Backplane Controls Supply Voltage from 9V to 0V Programmable Analog Foldback Current Limiting High