Cool-Switch® PI2161 60 Volt, 12 Amp Full-Function Load Disconnect Switch Solution Product Description Features The Cool-Switch® PI2161 is a complete full-function Load Disconnect Switch solution for medium voltage applications with a high-speed electronic circuit breaker and a very low on-state resistance MOSFET. It is designed to protect an input power bus from output load fault conditions. The PI2161 Cool-Switch solution is offered in an extremely small, thermally enhanced 7mm x 8mm LGA package. The PI2161 enables an extremely low power loss solution with fast dynamic response to an over current fault or high conditions. The PI2161 senses a small portion of the total MOSFET current and has a low voltage threshold allowing the use of low power sense resistors. • Integrated High Performance 12 A, 8.5 mΩ MOSFET The switch is closed when the EN input is low and is open when EN is high. Once enabled, the PI2161 monitors the MOSFET current through a sense resistor. If an over current level is sensed, the switch is quickly latched off to prevent the power source from being overloaded. Bringing the EN pin high will reset the over current latch allowing retry. The PI2161 has an internal 10 kΩ bias resistor connected between the Drain (D) and VC to eliminate need for external resistor in a 44 V bus application (41 V to 48 V). • Very small, high density fully-optimized solution with simple PCB layout • Programmable latching over-current detection • Fast 120ns disconnect response to load failures • Low loss current sensing • Fast disable via EN pin, typically 200 ns. • Load Status output (VO scaled load voltage) Applications • • • • N+1 Redundant Power Systems Servers & High End Computing Load Disconnect High Side Circuit Breaker Package Information • The PI2161 is offered in the following package: 17-pin 7mm x 8mm thermally enhanced LGA package, achieving <10°C/W RθJ-PCB Typical Application IOUT SH D EN SL EN PI2161 VC 0.1 µF PG GND VOUT SP SN CVC RS VO LOAD VIN VO RPG RVO Figure 2 — PI2161 response time to output short fault condition Figure 1 — PI2161 High Side Disconnect switch Cool-Switch® Rev 1.3 vicorpower.com Page 1 of 18 02/2014 800 927.9474 PI2161 Order Information Part Number Package Transport Media PI2161-01-LGIZ 7mm x 8mm 17-pin LGA T&R Absolute Maximum Ratings Note: Unless otherwise specified, all voltage nodes are referenced to “PG” Name Rating Drain-to-Source Voltages (VD to VSH and VSL) 60 V @ 25°C Source Current (ISH+ISL) Continuous 12 A @ 25°C Source Current (ISH+IS) Pulsed (10 μs) 100 A Source Current (ISH+IS) Pulsed (300 ns) [1] Single Pulse Avalanche Current (TAV<11 μs) [1] Junction-to-Ambient Thermal Resistance (RθJ-A) 150 A 33 A 45°C/W (0 LFM) Junction-to-PCB Thermal Resistance (RθJ-PCB) 10°C/W SH, SL, SP, SN to PG -0.3 V to 13 V / 20 mA SH to SL [4] ± 1.5 V VC to PG -0.3 V to 13 V / 10 mA Drain (D) to PG, Drain (D) to GND -0.3 V to 60 V / 10 mA VO, EN -0.3 V to 60 V / 1 mA Storage Temperature -65°C to 150°C Operating Junction Temperature -40°C to 140°C Internal MOSFET Operating Junction Temperature -40°C to 150°C Lead Temperature (Soldering, 20 sec) 250°C ESD Rating CDM Class IV [1] These parameters are not production tested but are guaranteed by design, characterization, and correlation with statistical process control. [4] A sense Resistor (Rs) has to be connected between SH and SL as shown in Figure 1, Rs ≤ 2 Ω. Cool-Switch® Rev 1.3 vicorpower.com Page 2 of 18 02/2014 800 927.9474 PI2161 Pin Description Pin Number Pin Name 1 EN Description Enable: Logic level input, active low allows switch to reach 8.5 mΩ typical in the on state within 2 ms. A logic high input will turn the switch off in typically 200 ns. Leave this pin open to allow switch to turn on after application of input power. Load Status Output: This pin pulls to the load voltage once the switch is enabled through an internal 2 VO 150 kΩ resistor. Connect a resistor from this pin to ground to scale the load voltage to the appropriate logic or analog level. Ground this pin if unused. 3 VC Voltage Bias: This pin is the supply pin for the control circuitry and gate driver. Connect a 0.1 μF capacitor between the VC pin and the PG pin. Voltage on this pin is regulated to 11.7 V with respect to PG by an internal shunt regulator. A 10 kΩ internal resistor (RD-VC) is connected between D pin and VC pin. 4 PG 5 SP Control Circuitry Return: PG is the floating return path for the controller circuitry. Connect this pin via a resistor to the GND (ground), as shown in Figure 1. Sense-Positive Input: Connect the SP pin to the SL pin side of the sense resistor as a Kelvin connection. The magnitude of the voltage difference between SP and SN provides an indication of the current through the sense resistor and the SL section of the MOSFET. 6,7 SL 8 SN Source Low: A low percentage of the internal N-channel MOSFET source current passes through this to the sense resistor. Refer to the Current Sense section in the Functional Description. Sense-Negative Input: Connect the SN pin to the SH pin side of the sense resistor as a Kelvin connection. The magnitude of the voltage difference between SP and SN provides an indication of the current through the sense resistor and the SL section of the MOSFET. 9, 10, 11, 17 SH 12, 13, 14, 16 D 15 GND Source High: The Source of the internal N-channel MOSFET section providing the majority of the load current and alternate bias to the control circuitry. Drain: The Drain of the internal N-channel MOSFET, connect to the input power source bus voltage that provides the current to the load. Ground: This pin is the return (ground) for the enable circuitry. Connect this pin to the logic/system power ground. Package Pin-Outs PI2161 Cool-Switch® Rev 1.3 vicorpower.com Page 3 of 18 02/2014 800 927.9474 PI2161 Electrical Characteristics Unless otherwise specified: -40°C < TJ < 125°C, VVC-PG = 10.5 V, VPG = VGND = 0 V, CVC = 0.1 μF Parameter Symbol Operating Supply Range Quiescent Current Quiescent Current at Start Up Clamp Voltage Clamp Shunt Resistance Under-Voltage Rising Threshold Under-Voltage Falling Threshold Under-Voltage Hysteresis VVC-PG IVC IVCSU VVC-CLM RSHUNT VVCUVLO VVCUVF VVCUV-HS Operating Supply Range D to VC resistance D input UVLO Rising Threshold VVD-GND RD-VC VVD-UVLO Conditions Control Circuit Supply (VC to PG) No VC limiting Resistor VC = 10.5 V, SP = SN = VC VC = 8.5 V, SP = SN = PG IVC = 3 mA Delta IVC = 10 mA VD = VVC , measure when VD = VSH Min Typ 8.5 Max Unit V mA mA V Ω V V mV 2.0 11 1.7 2.5 11.7 6.2 6 240 7.32 7.00 320 10.5 2.1 3.0 12.5 10 8.5 7.9 400 41 8 27 44 10 33 48 14 38 V kΩ V VVC +0.3 V 250 mV Drain Supply RPG = 6 kΩ RPG = 6 kΩ, ISH = -1 mA EN = 0 V Differential Amplifier and Comparators Common Mode Input Voltage Differential Operating Input Voltage [1] SP Input Bias Current SN Input Bias Current DBST Diode Forward Voltage (SN to VC) Low Range Overcurrent Threshold Low Range Overcurrent Turn-off Time High Range Overcurrent Threshold Overcurrent Hysteresis [1] Over Current Range switch over Threshold Over Current Range switch over delay [1]: Low to high Threshold Over Current Range switch over delay: High to low threshold Drain-to-Source Breakdown Voltage Source Current Continuous Drain to source Off State Current Drain-to-Source On Resistance Current Sense Ratio [3] VCM VSP-SN ISP ISN VDBST VOC-THL TOC-OFF VOC-THH VOC-HY VPG SP-SN SP = SN = VC SP = SN = VC 15 25 35 50 0.87 1.0 133 9 70 120 166 13 77 200 200 17 mV ns mV mV ISN = 3 mA VC-SN = 0 V VSP-SN = 0~200 mV step to 90% of VSH max, SN = VC VC-SN = 6 V μA μA 25 37 63 V VSOTH VC-SN 0.5 0.8 1 V TSOL2H VC-SN = -0.7 V~1.7 V 100 170 300 ns TSOH2L SN-VC = -1.7 V~0.7 V 80 125 190 ns BVDSS ISH+ISL IDS-OFF RDSon KS Internal N-Channel MOSFET ID = 2 mA, Tj = 25°C In ON state, Tj=25°C EN = 3.3 V, VD = 44 V, VSH = VSL = 0 V In ON state, ID = 10 A. Tj = 25°C ISL/ (ISH+ISL), ID = 10 A [4] 3.2 8.5 12 4.3 11 8 V A mA mΩ % Cool-Switch® Rev 1.3 vicorpower.com Page 4 of 18 02/2014 800 927.9474 60 PI2161 Electrical Characteristics (Cont.) Unless otherwise specified: -40°C < TJ < 125°C, VVC-PG = 10.5 V, VPG = VGND = 0 V, CVC = 0.1 μF Parameter DClamp Forward voltage Symbol VF Conditions Min Typ Internal Schottky Diode (between PG and SH) VF = 10 mA, Tj = 25°C Max Unit 400 mV 158 5 kΩ μA 1.6 V μA Load Status Voltage (VO) Source (SH) to VO resistance Source to VO leakage RSH-VO IVOLK 142 150 Enable ( EN ) Threshold Voltage Input bias @ 3.3 V VEN 0.4 50 IEN [1] These parameters are not production tested but are guaranteed by design, characterization, and correlation with statistical process control. [2] Current sourced by a pin is reported with a negative sign. [3] Refer to the Current Sense section in the Functional Description. [4] A sense Resistor (Rs) has to be connected between SH and SL as shown in Figure 1, Rs ≤ 2 Ω. Cool-Switch® Rev 1.3 vicorpower.com Page 5 of 18 02/2014 800 927.9474 PI2161 The PI2161 integrated Cool-Switch product takes advantage of two different technologies combining low RDS(on) N-channel MOSFETs with high density control circuitry to provide a high side fast Circuit Breaker solution. The PI2161’s 8.5 mΩ on state resistance MOSFET minimizes the voltage drop, at the maximum rated current of 12 A, significantly reducing power dissipation and eliminating the need for heat sinking. As shown in the typical application Figure 1 and the block diagram Figure 5, the unique aspect of the load current sensing scheme is that only a small portion of the total MOSFET source current is routed through the sense resistor (Rs). This allows using a much lower power component compared to the conventional method of sensing the total current to the load. Figure 5, Figure 6 and Figure 7 show the PI2161 block diagram, timing diagram and state diagram respectively. Differential Amplifier The PI2161 integrates a high-speed fixed offset voltage differential amplifier to sense the difference between the Sense Positive (SP) pin and Sense Negative (SN) pin voltage. The amplifier output is connected to the control logic that determines the state of the fault latch. To avoid tripping the breaker due to load capacitance during initial power up, a higher threshold (VOC-THH) is used. The amplifier will detect if the drop across the sense resistor reaches 166 mV and discharge the gate of the MOSFET if detected. Once the load voltage approaches the input potential, the threshold (VOC-THL) is lowered to 70 mV. This allows for capacitive load charging and continuous current sensing without the use of a sense blanking timer. Current Sense The PI2161 internal MOSFET source is split into two portions, Source High current (SH) and Source Low current (SL). SH conducts the majority of the current and SL conducts a small portion of the load current. SL current is routed through the sense Resistor (Rs) for current sensing. Current Sense Ratio (Ks) [%] Functional Description 6.0 5.8 5.6 Ju n 5.4 5.2 5.0 Ju 4.8 4.6 on tio n Te m Te m pe pe 4.0 3.8 ra t u re ra t ure =1 =2 25 °C 5°C 40 50 60 70 80 90 100 110 120 130 140 150 Sense Resistor Value (mΩ) Figure 3 — Current ratio vs. sense resistor over temperature Figure 4 characterizes the trip current range between 25°C and 125°C over a range of sense resistor values. The equations and an example for calculating Rs value for a trip current level and the equation for the trip current at a given sense resistor value are provided in the Application Information section. Enable Input (EN) This input provides control of the switch state enabling and disabling with logic level signals. The active low feature allows grounding or floating of the input resulting in switch closure upon application of input power. System control can disable the switch and reset the over current latch by pulling this pin to a logic high state. Once enabled the load voltage will reach the input voltage in typically 1 ms and the device will sense the current continuously once the POR interval has cleared relative to the VC to PG potential. The disable control with this input is very fast, turning the switch off in typically 200 ns. The response to open during an over current event is typically 120 ns and the switch will latch off until reset by bringing this input high or recycling of the input power. 40 38 Overcurrent Threshold = 70 mV Typical RDS(on) at 25°C = 8.5 mΩ 36 34 32 30 28 26 24 22 20 Ju n c 18 Ju n c 16 14 12 Where: tion T e mp eratu re = tion T 25°C emp eratu re = 1 25° C 10 30 RS : RDS(on): KS: ISL: ILoad: cti nc 4.4 4.2 30 Over Current Trip (A) 12 • R DS ( on ) I K S = SL = I Load 144 • R DS ( on ) + ( Rs + 17.5) • (11) Typical RDS(on) at 25°C = 8.5 mΩ 3.6 3.4 3.2 The value of the sense Resistor in the path of the sense current, will create a voltage drop and have an effect on the current ratio KS. The current ratio is expressed in the following equation as a function of RDS(on) and Rs. Note that the MOSFET RDS(on) value is temperature dependent and temperature will effect the current ratio. For one RDS(on) value the current ratio is constant with respect to the load current. Current ratio vs. sense resistor over temperature performance is shown in Figure 3. 6.6 6.4 6.2 Sense Resistor value in [mΩ] MOSFET ON resistance value [mΩ] Current sense ratio SL sense current [A] Load Current [A] 40 50 60 70 80 90 100 110 120 130 140 150 Sense Resistor Value (mΩ) Figure 4 — Over current trip vs. sense resistor over temperature Cool-Switch® Rev 1.3 vicorpower.com Page 6 of 18 02/2014 800 927.9474 PI2161 VC Voltage Regulator and MOSFET Drive The biasing scheme in the PI2161 uniquely enables the gate control relative to the PG pin via the resistor RPG shown in Figure 1. The VC input provides power to the control circuitry, the charge pump and the gate driver. An internal regulator clamps the VC voltage to 11.7 V with respect to PG. The internal regulator circuit has a comparator to monitor VC voltage and pulls the gate low when VC to PG is lower than the VC Under-Voltage Threshold. During start up or in a fault condition when the output (Load) is shorted, the VC pin is biased through a 10 KΩ (RD-VC) internal resistor connected to the drain of the MOSFET. The VC pin will be biased through the load potential once the MOSFET is enabled. In a high voltage application as shown in Figure 1 the lower bias resistor RPG placed between the PG pin and system ground is required. RPG creates an offset voltage at the PG pin to regulate VC with respect to PG when the MOSFET is enabled and the load voltage reaches the input voltage. The PI2161 has an integrated charge pump that approximately doubles the regulated VC with respect to PG enhancing the NChannel MOSFET gate to source voltage. The internal gate driver controls the N-channel MOSFET such that in the on state, the gate driver applies current to the MOSFET gate driving it to bring the load up to the input voltage and into the RDS(on) condition. When an over current condition is sensed the gate driver pulls the gate low to PG and discharges the MOSFET gate with 4 A peak capability. Load Status (VO) When the Gate is enabled, a 150 kΩ resistor is connected to the MOSFET source and VO. An external resistor between VO and ground creates a voltage divider that scales the load voltage down to the desired level to interface with the diagnostic circuit to represent a logic state or analog voltage level. The external resistor RVO can be calculated using the following equation: RVO = 150KΩ • VO VSH − VO Where: VO : Desired voltage level at VO pin VSH: Enabled load or SH voltage Cool-Switch® Rev 1.3 vicorpower.com Page 7 of 18 02/2014 800 927.9474 PI2161 Figure 5 — PI2161 block diagram Initial Power-up Disabled Over Current Reset VIN Latched EN VC Internal Gate Over Current Threshold IOUT VOUT VO Scaled VSH Figure 6 — PI2161 timing diagram, referenced to Figure 1 Cool-Switch® Rev 1.3 vicorpower.com Page 8 of 18 02/2014 800 927.9474 Latched PI2161 Figure 7 — PI2161 State Diagram, referenced to Figure 1 Cool-Switch® Rev 1.3 vicorpower.com Page 9 of 18 02/2014 800 927.9474 PI2161 Typical Characteristics 1.15 1.76 VVC-PG = 10.5 V VC Quiescent Current (mA) 1.74 1.10 1.72 ID = 2 mA 1.70 1.05 1.68 1.66 1.00 1.64 1.62 0.95 1.60 0.90 1.58 -50 -25 0 25 50 75 100 125 -50 150 -25 75 100 125 150 1.5 70.0 IS = 12 A 1.4 69.5 RDS(on) (Normalized) 69.0 68.5 68.0 1.3 1.2 1.1 1.0 0.9 VVC-PG = 10.5 V 67.5 0.8 VC = SN 67.0 0.7 -25 0 25 50 75 100 125 150 -50 Junction Temperature (°C) -25 0 25 50 75 100 125 150 Junction Temperature (°C) Figure 9 — Low Range Overcurrent Threshold vs. temperature Figure 12 — Internal MOSFET on-state resistance vs. temperature 100 130 VSp-SN = 0 to 200 mV step 128 124 122 120 118 10 TJ = 15 0° C IS - Source Current (A) SN = VC 126 TJ = 25°C Low Overcurrent Threshold (mV) 50 1.6 70.5 Low Overcurrent Turn-off Time (ns) 25 Figure 11 — Internal MOSFET drain to source breakdown voltage vs.temperature Figure 8 — Controller bias current vs. temperature -50 0 Junction Temperature (°C) Junction Temperature (°C) 116 1 114 -50 -25 0 25 50 75 100 125 0.2 150 Junction Temperature (°C) Figure 10 — Low Range Overcurrent Turn-off time vs. temperature 0.4 0.6 0.8 1.0 1.2 Vf-BD - Diode Forward Voltage (V) Figure 13 — Internal MOSFET source to drain diode forward voltage (pulsed ≤300 µs). Cool-Switch® Rev 1.3 vicorpower.com Page 10 of 18 02/2014 800 927.9474 PI2161 Thermal Characteristics 150 150 Air Flow = 0 LFM Rds(on)max = 11 mΩ @ 25°C 130 RθJA = 45°C/W 120 110 1 TA = 100 00°C 9 TA = 90 TA = 80 0°C 80°C 70°C TA = 60°C TA = 50°C TA = 70 60 1 2 3 Rds(on)max = 11 mΩ @ 25°C 130 RθJA = 35°C/W 120 110 1 TA = 100 0°C 8 TA = 80 0°C 70°C TA = 60°C TA = 50°C TA = 70 50 4 5 6 7 8 9 0 10 11 12 1 2 3 4 5 Figure 14 — MOSFET Junction Temperature vs. Input Current for a given ambient temperature (0 LFM) 13 12 8 ; Ma mΩ 7 6 x TJ Input Current (A) 9 = 11 5 = 12 FM ,R m Ω FM DS =1 ,R 1m DS Ω =1 1m Ω Ω m 8. 5 5 8. = 10 ax = 7 DS S 8 ,R 0L D 0L ,R M LF 9 LF M 10 11 12 R DS(on)m 0 20 9 11 20 10 8 RDS(on)max = 11 mΩ; Max TJ = 150°C 12 0 7 Figure 16 — MOSFET Junction Temperature vs. Input Current for a given ambient temperature (200 LFM) 13 11 6 Input Current (A) Input Current (A) Input Current (A) 00°C 9 TA = 90 60 50 0 Air Flow = 200 LFM 140 Junction Temperature (°C) Junction Temperature (°C) 140 6 5°C 4 3 5 2 45 55 65 75 85 95 105 115 80 125 90 100 110 120 130 140 150 Ambient Temperature (°C) Ambient Temperature (°C) Figure 17 — PI2161 input current de-rating vs. PCB temperature, for the MOSFET maximum TJ at 125°C and 150°C Figure 15 — PI2161 input current de-rating based on the MOSFET maximum TJ = 150°C vs. ambient temperature MOSFET PI2161 Figure 18 — PI2161 mounted on a 1in2 pad of 0.5 oz copper. Thermal Image picture, IOUT = 10 A, TA = 25°C, Air Flow = 0 LFM Cool-Switch® Rev 1.3 vicorpower.com Page 11 of 18 02/2014 800 927.9474 PI2161 Figure 19 — PI2161 response to an increase in load current Application Information The PI2161 Cool-Switch is a medium voltage high side load disconnect switch. This section describes in detail the procedure to follow when designing with the PI2161 load disconnect switch. Lower Bias Resistor selection: RPG As described in Functional Description section, in a floating application as shown in Figure 1 the lower bias resistor RPG placed between the PG pin and system ground is required. RPG creates an offset voltage at the PG pin to regulate VC with respect to PG when the MOSFET is enabled. The RPG resistor can be calculated using the following expression: R PG = Controller maximum VC bias current. 2.1 mA 100 μA: 100 μA is added for a margin Example: 41 V < VIN < 48 V Make sure that the PI2161 to turn on below the minimum required voltage, use 27 V for the minimum voltage to calculate RPG. RPG = 27V − 12.5V − 1V = 6.136KΩ or 6.04KΩ 2.1mA + 100μA Pd RPG = (48V − 11V ) 2 = 227mW 6.04 KΩ Enable Input: (EN) This input provides control of the switch state enabling and disabling with logic level signals. VVD −UVLO min − VC clampMAX − V DBST − MAX I VCMAX + 100μA The RPG worst case condition for power dissipation is a function of the maximum BUS voltage and minimum VC clamp voltage. Where: Pd RPG = IVCMAX: (Vinmax − VC clampMIN ) 2 R PG VVD-UVLO min: Drain input UVLO minimum voltage, 27 V VINMAX: Vin maximum voltage, 48 V VCClampMax: Controller maximum VC clamp voltage, 12.5 V VDBST-MAX: Maximum DBST Forward Voltage, 1.0 V VCClampMin: Controller minimum VC clamp voltage, 11 V Current Sense Resistor Selection: Rs The Rs value can be selected from Figure 4 to set the nominal trip current at junction temperature for internal MOSFET of 25°C or 125°C. To set the minimum trip current at specific junction temperature use the following procedure. The current trip point is a function of the Low Range Overcurrent Threshold (VOC-THL), the internal MOSFET on resistance (RDS(on)) and current sense resistor (Rs). To insure that PI2161 will not trip within the expected nominal operating current range, include the variation of VOC-THL and RDS(on) in the calculation when selecting Rs. VOC-THL is 70 mV typical, 63 mV minimum and 77 mV maximum. The RDS(on) typical value at 25°C is 8.5 mΩ and 11 mΩ maximum. RDS(on) will increase with temperature as shown in Figure 12, and can be calculated by multiplying the RDS(on) value at 25°C by the normalized factor in Figure 12 at the expected operating junction temperature or use the following equation: Cool-Switch® Rev 1.3 vicorpower.com Page 12 of 18 02/2014 800 927.9474 PI2161 ( ) −3 RDS (on) (TJ ) = RDS (on) (25°C) • 0.873 • e 3.75• TJ •10 + 0.041 Where: This is a low power dissipation resistor and any package size work as far by selecting the nearest standard value. The closest resistor available value in 1% accuracy in an 0603 or 0805 package is 0.10 Ω (100 mΩ). If 0603 0.10 Ω 1% resistor selected, then the minimum trip current is: TJ : Internal MOSFET Junction temperature RDS(on) : Internal MOSFET RDS(on) at TJ in °C RDS(on): Internal MOSFET RDS(on) at TJ = 25°C I TRIP = 63 • (144 • 14.42 + 11 • (100 + 17.5) ) = 12.26 A 12 • 100 • 14.42 The sense resistor can be calculated from the following equation as a function of the trip current: Rs = Internal N-Channel MOSFET BVDSS VOC _ THL • (144 • R DS ( on ) + 192.5) 12 • I TRIP • R DS ( on ) − 11 • VOC _ THL And the trip current can be calculated from the following equation: I TRIP = VOC _ THL • (144 • R DS ( on ) + 11 • ( Rs + 17.5) ) In load disconnect switch applications when the load is shorted, a large current is sourced from the input supply through the MOSFET. Depending on the input impedance of the system and the parasitic inductance, the current in the MOSFET may exceed the source pulsed current rating (150 A) just before the PI2161 MOSFET is turned off. 12 • Rs • R DS ( on ) Sense resistor Maximum power dissipation is: Pd RS = VTH − MAX Rs 2 The peak current during an output short condition is calculated as follows, assuming that the output has very low impedance and it is not a limiting factor: Where: Rs: ITRIP: VOC_THL: VTH-MAX: The PI2161’s internal N-Channel MOSFET breakdown voltage (BVDSS) is rated for 60 V at 25°C and will degrade to 55.5 V at -40°C, refer to Figure 11. Drain to source voltage should not exceed BVDSS in nominal operation. During a fast switching transient the MOSFET can tolerate voltages higher than its BVDSS rating under avalanche conditions. Refer to the Absolute Maximum Ratings table. Current sense resistor [mΩ] Current trip point [A] Low Range Overcurrent Threshold [mV], 63 mV minimum Maximum Overcurrent Threshold [mV], 77 mV Current trip calculation example: Minimum current tripping point = 12 A I PEAK = V D • t OC −OFF L PARASITIC Where: IPEAK: Peak current in PI2161 MOSFET before it is turned off VD: Input voltage or load voltage at D pin before input short condition did occur Maximum MOSEFET junction temperature = 100°C. The lowest tripping current will occur at the internal MOSFET maximum RDS(on) and its maximum junction temperature, and minimum Low Range Overcurrent Threshold (VOC-THL). The MOSET maximum RDS(on) is 11mΩ at 25°C and at maximum junction temperature will be: ( −3 ) RDS (on) (100) = 11mΩ • 0.873 • e 3.75 •100 •10 + 0.041 R DS ( on ) (100 ) = 14.42 mΩ Select Rs at minimum VOC-THL =63 mV Rs = tOC-OFF: Low Range Overcurrent Turn-off Time. LPARASITIC: Circuit parasitic inductance The high peak current during an output short and before the MOSFET turns off, stores energy in the circuit parasitic inductance, and as soon as the MOSFET turns off, the stored energy at the drain side of the internal MOSFET will be released to produce a voltage higher than the input voltage while the MOSFET source is at ground. This event will create a high voltage difference between the drain and source of the MOSFET. The MOSFET will avalanche, but this avalanche will not affect the MOSFET performance because the PI2161 has a fast response time to the input fault condition and the stored energy will be well below the MOSFET avalanche capability. MOSFET avalanche energy during an output short event is calculated as follows: 63 • (144 • 14.42 + 192.5) = 103.32mΩ 12 • 12 • 14.42 − 11 • 63 E AS = Rs maximum power dissipation: 1.3 • BV DSS 1 2 • • LPARASITIC • I PEAK 2 1.3 • BV DSS − VS Where: 2 Pd RS V 0.077 2 = TH − MAX = = 57.6mW Rs 0.103 EAS: Avalanche energy BVDSS: MOSFET maximum rated voltage (60 V) Cool-Switch® Rev 1.3 vicorpower.com Page 13 of 18 02/2014 800 927.9474 PI2161 Power dissipation In Load Disconnect Switch applications, the MOSFET is on in steady state operation and the power dissipation is derived from the total source current and the on-state resistance of the MOSFET. The PI2161 internal MOSFET power dissipation can be calculated with the following equation: Pd MOSFET = Is 2 • RDS (on) Source Current PdMOSFET: MOSFET power dissipation RDS(on): MOSFET on-state resistance R PG = VVD −UVLO min − VC clampMAX − V DBST − MAX I VCMAX + 100μA 27V − 12.5V − 1V = 6.136kΩ 2.1mA + 0.1mA The closest 1% resistor available is 6.04 kΩ, RPG power dissipation will be: Where: Is: R PG = PdR PG = Note: For the worst case condition, calculate with maximum rated RDS(on) at the MOSFET maximum operating junction temperature because RDS(on) is temperature dependent. Refer to Figure 12 for normalized RDS(on) values over temperature. The PI2161 maximum RDS(on) at 25°C is 11 mΩ and will increase by 43% at 125°C junction temperature. The Junction Temperature rise is a function of power dissipation and thermal resistance. (V S − max − V S − PGMin ) 2 (50V − 11V )2 = = 252mW R PG 6.04 kΩ The selected resistor should be capable of supporting the total power at maximum operating temperature, 60°C. An 0805 (2012) will support the power requirement. VO pin In this application use the minimum voltage output VSH = 40 V, and for VO use the logic high voltage (2.0 V) with margin, VO = 2.1 V RVO = 150KΩ • Trise = RθJA • Pd MOSFET = RθJA • Is 2 • RDS (on) Closest 1% resistor is 8.45 kΩ to the high side Calculate VO at VSH = 40 V and RVO=8.45 kΩ Where: RqJA : 2.1V = 8.3KΩ 40V − 2.1V Junction-to-Ambient thermal resistance (45°C/Watt) This calculation may require iteration to get to the final junction temperature. Figure 14 and Figure 16 show the PI2161 internal MOSFET final junction temperature curves versus conducted current at maximum RDS(on), given ambient temperatures and air flow. VO = VSH • RVO 150KΩ + RVO VO = 40V • 8.45 KΩ = 2.133 V 150KΩ + 8.45 KΩ Load Status Resistor Selection: (RVO) RVO can be calculated using the following equation: RVO = 150KΩ • VO VSH − VO Typical Application Example Load Disconnect Switch Requirement Bus Voltage = 45 V ±5 V Maximum Load Operating Current = 9 A Minimum Trip Current = 10 A Maximum Ambient Temperature = 60°C, no air flow (0 LFM) The current flow parasitic inductance is 60 nH. System logic voltage is 3.3 V and logic high = 2.0 V Solution In this application, PI2161 is used to protect the power source from load failure, configured as shown in the circuit schematic in Figure 21. RPG Selection For a margin purpose, select RPG to operate at input voltage below the required operating voltage, use 27 V minimum operating voltage: Power Dissipation and Junction Temperature First use Figure 14 (MOSFET Junction Temperature vs. Input Current) to find the final junction temperature for 9 A load current at 60°C ambient temperature. In Figure 14 (illustrated in Figure 20) draw a vertical line from 9 A to intersect the 60°C ambient temperature line. At the intersection draw a horizontal line towards the Y-axis (Junction Temperature). The Junction Temperature at maximum load current (9 A) and 60°C ambient is 115°C. RDS(on) is 11 mΩ maximum at 25°C and will increase as the Junction temperature increases. From Figure 12, at 115°C RDS(on) will increase by 38%, then maximum at 115°C. Maximum power dissipation is: Pdmax = Iin2 • RDS (on) = (9 A)2 • 15.18mΩ = 1.23W Recalculate TJ: ⎞ ⎛ 45°C TJ max = 60°C + ⎜ ∗ (9 A) 2 • 15.18mΩ ⎟ = 115.3°C ⎠ ⎝ W Cool-Switch® Rev 1.3 vicorpower.com Page 14 of 18 02/2014 800 927.9474 PI2161 Junction Temperature (°C) 150 Air Flow = 0 LFM 140 133 130 Rds(on)max = 11 mΩ @ 25°C o RθJA = 45°C/W 120 115 110 o C 100 ° TA = ° 0 9 C TA = 80°C TA = 70°C TA = 60°C TA = 50°C TA = 100 90 80 70 60 PI2161 50 0 1 2 3 4 5 6 7 8 9 10 11 12 Input Current (A) Figure 20 — Example 1 final MOSFET junction temperature at 9 A/60°C TA Figure 21 — PI2161 configured for 10A minimum trip current Select Rs The minimum trip current will occur at maximum MOSFET junction temperature and VOC-THL = 63 mV: MOSFET Junction Temperature for 10 A at 60°C can be estimated using the graph in Figure 14 as illustrated in Figure 20. Draw a vertical line from 10 A to intersect the 60°C ambient temperature line. At the intersection draw a horizontal line towards the Y-axis (Junction Temperature). The Junction Temperature at maximum load current (10 A) and 60°C ambient is 133°C. Layout Recommendation ( ) −3 RDS (on) (TJ ) = RDS (on) (25°C) • 0.873 • e 3.75 •TJ • 10 + 0.041 Use the following general guidelines when designing printed circuit boards. An example of the typical land pattern for the PI2161 is shown in Figure 22. • Use a solid ground (return) plane to reduce circuit parasitic. • Connect Rs terminal at SN pin side and all S pads together with a wide trace to reduce trace parasitics and to accommodate the high current output, and also connect all D pads together with a wide trace to accommodate the high current input. • Kelvin connect SP pin and SN pin to Rs terminals to the S pins. • Connect SL pins together with a wide trace connect them to Rs. ( −3 ) RDS (on) (133) = 11mΩ • 0.873 • e 3.75•133 •10 + 0.041 • Use 1oz of copper or thicker if possible to reduce trace resistance and reduce power dissipation. R DS ( on ) (133) = 16.26 mΩ Rs = Rs = • Place CVC very close to PI2161 to have very short traces to PI2161 pins without any PCB via in between. VOC _ THL • (144 • R DS ( on ) + 192.5) 12 • I TRIP • R DS ( on ) − 11 • VOC _ THL 63 • (144 • 16.26 + 192.5) = 126.9mΩ 12 • 10 • 16.26 − 11 • 63 The closest 1% resistor available off-the-shelf is 130 mΩ. The minimum trip current is: I TRIP = I TRIP = VOC _ THL • (144 • R DS ( on ) + 11 • ( Rs + 17.5) ) 12 • Rs • R DS ( on ) 63 • (144 • 16.26 + 11 • (130 + 17.5) ) = 9.85 A 12 • 130 • 16.26 Figure 22 — PI2161 layout recommendation Cool-Switch® Rev 1.3 vicorpower.com Page 15 of 18 02/2014 800 927.9474 PI2161 Package Drawings Cool-Switch® Rev 1.3 vicorpower.com Page 16 of 18 02/2014 800 927.9474 PI2161 Footprint Recommendation Cool-Switch® Rev 1.3 vicorpower.com Page 17 of 18 02/2014 800 927.9474 PI2161 Vicor’s comprehensive line of power solutions includes high density AC-DC and DC-DC modules and accessory components, fully configurable AC-DC and DC-DC power supplies, and complete custom power systems. Information furnished by Vicor is believed to be accurate and reliable. However, no responsibility is assumed by Vicor for its use. Vicor makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication. Vicor reserves the right to make changes to any products, specifications, and product descriptions at any time without notice. Information published by Vicor has been checked and is believed to be accurate at the time it was printed; however, Vicor assumes no responsibility for inaccuracies. Testing and other quality controls are used to the extent Vicor deems necessary to support Vicor’s product warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. Specifications are subject to change without notice. Vicor’s Standard Terms and Conditions All sales are subject to Vicor’s Standard Terms and Conditions of Sale, which are available on Vicor’s webpage or upon request. Product Warranty In Vicor’s standard terms and conditions of sale, Vicor warrants that its products are free from non-conformity to its Standard Specifications (the “Express Limited Warranty”). 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Life Support Policy VICOR’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL COUNSEL OF VICOR CORPORATION. As used herein, life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness. Per Vicor Terms and Conditions of Sale, the user of Vicor products and components in life support applications assumes all risks of such use and indemnifies Vicor against all liability and damages. Intellectual Property Notice Vicor and its subsidiaries own Intellectual Property (including issued U.S. and Foreign Patents and pending patent applications) relating to the products described in this data sheet. No license, whether express, implied, or arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Interested parties should contact Vicor's Intellectual Property Department. The products described on this data sheet are protected by the following U.S. Patents Number: 6,898,092 Vicor Corporation 25 Frontage Road Andover, MA 01810 USA Picor Corporation 51 Industrial Drive North Smithfield, RI 02896 USA email Customer Service: [email protected] Technical Support: [email protected] Cool-Switch® Rev 1.3 vicorpower.com Page 18 of 18 02/2014 800 927.9474