Application Note September 2001 AN9959 InfiniBand architecture re
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InfiniBand Class Power Supply Using ISL6160 HIP6006
Application Note September 2001 AN9959
InfiniBand architecture represents significant evolution high-performance, switched-fabric interconnect systems. goal provide high-performance, reliable, scalable connect high-end servers each other subsystems, routers switches that connect world outside data center. Available from Intersil ISL6160, evolution power sequencing, control protection InfiniBand modules (IM). ISL6160 designed address unique power requirements InfiniBand (IB) industry initiative providing independent power control both (bulk) (+12V) (auxiliary) (+5V) power rails single port. This device implemented both Class (non isolated) Class (isolated) Power Topology applications. Intersil also provides ISL6160EVAL2 concept evaluation platform. ISL6160EVAL2 complete InfiniBand Class (non isolated) power topology evaluation platform which highlights operation ISL6160 HIP6006 single output controller. Figure simplified block diagram ISL6160EVAL2 platform. This evaluation platform allows InfiniBand Module (IM) power supply designer evaluate concept this design apply this concept specific power requirement. evaluation platform configured Vout 3.5A Iout capability where exhibits efficiency 85%, small area. Figure complete ISL6160EVAL2 schematic.
supply rail from sudden in-rush current. During turn-on, external gate capacitor N-Channel MOSFET, switch) charged with 20µA current source resulting programmable ramp (soft start turn-on). internal charge pump supplies gate drive supply switch driving MOSFET gate +5V. Once Secondary Rail ramps DC-DC_En pulled high thus enabling accompanying voltage converter. DC-DC converter then provides well regulated output voltage load. evaluation either electronic passive load suitable suppling load current. ISL6160 undervoltage lockout feature prevents turn-on until VA_In 2.5V. then enables soft start power rising voltage output current limited ramp that both inrush current voltage slew rate limited, independent load. This reduces supply droop surge eliminates need additional external filters. During operation, once condition detected output current limited 12ms allow transient conditions pass. still current limit after current limit period elapsed, output then latched off. circuitry latched until reset disconnection reconnection from chassis backplane.
VB_IN
DC-DC_ON VB_ON VA_IN
UGATE Vout
ISL6160
HIP6006
LGATE
Using ISL6160EVAL2 Concept Board
ISL6160EVAL2 consists load boards, representing chassis respectively. board terminals supplies. load board with staggered length connector fingers emulate connector then plugs into socket shown Figure When load board inserted into board, stagger connector fingers, first provides VX_RET, then connections, finally shortest finger emulates VBx_En_L line connection. Once VB_In connected control portion circuit biased Secondary Rail (TP1) held until ISL6160 VB_ON signaled high. Local power enable signaling provided through LCL_PWR_EN jumper either hard `high' with jumper installed through external input signal, with jumper removed. single logic gate provides XORing VBxEN local power enable signals into ISL6160 VB_ON pin. time VB_ON asserted high ISL6160 turns Secondary Rail soft start mode protecting primary
VAout RLOAD
FIGURE ISL6160EVAL2 BLOCK DIAGRAM
Secondary Rail enabled once VB_ON (TP7) signalled high (through assertion local power enable), then DC-DC (TP2) pulled high network allows setting DC-DC converter enabling signal level ramp, thus customizing time DC-DC enabling. Once DC-DC enabled output (TP3) ramps output supplied with banana jack connecting external active passive load. Figure illustrates typical operational waveforms ISL6160EVAL2. These accessible through labeled test points (TPX) eval board. Figures ISL6160EVAL2 turn-on turn-off output voltage waveforms.
CAUTION: These devices sensitive electrostatic discharge; follow proper Handling Procedures. 1-888-INTERSIL 321-724-7143 Intersil Design trademark Intersil Americas Inc. Copyright Intersil Americas Inc. 2001, Rights Reserved
Application Note AN9959
LCL_PWR_EN (TP6)
Secondary Rail (TP1)
VGATE (TP4)
DC-DC_EN (TP2) Vout (TP3) Iout DIV)
FIGURE ISL6160EVAL2 Vout TURN-OFF
ISL6160EVAL2 Performance
FIGURE ISL6160EVAL2 PHOTOGRAPH
Efficiency
Figure displays ISL6160EVAL2 efficiency versus load current. highlights efficiency advantages switching regulator higher load current. designed current limit this evaluation ~3.5A. dashed portion curve collected from modified evaluation board with increased overcurrent protection limit. curve indicates maximum efficiency about 4.5A output current approximately input power.
IOUT (1A/DIV) INPUT CURRENT (1A/DIV)
VPHASERAIL 5V/DIV (10V/DIV) (TP9)
RAIL (5V/DIV)
EFFICIENCY
VOUT (5V/DIV) (TP3)
TIME (4µs/DIV)
FIGURE ISL6160EVAL2 OPERATIONAL WAVEFORMS
MEAN CURRENT INTO SWITCH MEAN LOAD CURRENT VOUT
LCL_PWR_EN (TP6) VGATE (TP4)
LOAD CURRENT
FIGURE ISL6160EVAL2 EFFICIENCY LOAD CURRENT
Secondary Rail (TP1)
DC-DC_EN (TP2) Vout (TP3)
ISL6160 related efficiency improvements only come from lowering RDSon (Q3) switch threshold voltage across sense resistor that invokes current regulation shutdown. HIP6006 related efficiency improvements explained Power Supply Design Considerations section this document.
Transient Response
20ms
FIGURE ISL6160EVAL2 Vout TURN-ON
Figure shows laboratory oscillogram ISL6160EVAL2 response 0-3.5A, 250A/ms load transient. output voltage responds rapidly within nominal value less than 150µs.
Application Note AN9959
This lower limit based achieved efficiency down stream converter design max. power capability that converter output. point failure, providing lower current regulation limit module risk passing through rail voltage disruptions reduced eliminated having rely overhead capacity chassis supply. HIP6006 Protection
ILOAD (2A/DIV)
VOUT (1V/DIV) VOUT (200mV/DIV)
TIME (40us/DIV)
FIGURE ISL6160EVAL2 TRANSIENT RESPONSE
HIP6006 loss less overcurrent (OC) protection feature. This accomplished current-sense function HIP600x family. HIP6006 senses converter load current monitoring drop across upper MOSFET (Q2a Figure schematic) enhancing converter's efficiency reducing cost eliminating current sensing resistor. over-current function cycles soft-start function hiccup mode provide fault protection. resistor (ROCSET, programs over-current trip level. internal 200µA (typical) current sink develops voltage across ROCSET that referenced secondary rail. When voltage across upper MOSFET (also referenced secondary rail) exceeds voltage across OCSET, over-current function initiates soft-start sequence. soft-start function discharges with 10µA current sink inhibits operation. soft-start function recharges CSS, operation resumes with error amplifier clamped voltage. Should overload occur while recharging CSS, soft start function inhibits operation while fully charging complete cycle. converter dissipates very little power with this method. over-current function will trip peak inductor current (IPEAK) determined
OCSET OCSET PEAK
Output Current Voltage Ripple
output current voltage ripple HIP6160EVAL2 shown Figure load current 3.5A this oscillogram. Peak-to-peak voltage ripple about 60mV under these conditions.
VOUT (50mV/DIV)
ILOAD (50mA/DIV)
TIME (2us/DIV)
FIGURE ISL6160EVAL2 OUTPUT RIPPLE
Protection
With ISL6160EVAL2 Class power supply concept there areas protection. ISL6160 limits current into port, whereas HIP6006 will limit current load. ISL6160 Protection ISL6160EVAL2 designed input current limit 2.8A, max. specified peak current port. This allows maximum output current ~3.5A output voltage. Iout increases above 3.5A input current ripple peaks increase limited 2.8A, beyond this point ISL6160 reduces gate drive current regulation (CR), causing decrease overall efficiency protecting primary rail. lower limit based particular needs implemented `tighten' power budget control.
where IOCSET internal OCSET current source (200µA typical). trip point varies mainly MOSFETs rDS(ON) variations. avoid over-current tripping normal operating load range, find OCSET resistor from equation above with: maximum rDS(ON) highest junction temperature. minimum IOCSET from specification table. Determine IPEAK PEAK where output inductor ripple current.
small ceramic capacitor should placed parallel with ROCSET smooth voltage across ROCSET presence switching noise input voltage. Figure illustrates ISL6160EVAL2 operational waveforms. DC-DC output shorted
Application Note AN9959
HIP6006 current limits When Secondary Rail voltage decreases 10V(TP1) ISL6160 deasserts DC-DC_EN (TP2) shuts converter. 1.6ms delay prevent spurious events from latching power supply. RFP45N06's gain switching losses offsets decreased conduction losses load currents about This data reinforces need consider both switching conduction losses MOSFETs. This data taken from HIP6006EVAL1 platform.
IOUT (1A/DIV) EFFICIENCY
SECONDARY RAIL (5V/DIV)
PRIMARY RAIL 5V/DIV
RFP25N05 RFP45N06
VOUT (5V/DIV) DC-DC_EN (5V/DIV) TIME (0.4ms/DIV) LOAD CURRENT
FIGURE ISL6160EVAL2 OVER-CURRENT OPERATION
FIGURE HIP6006EVAL1 EFFICIENCY WITH EITHER RFP25N05 RFP45N06 MOSFETs
Power Supply Design Considerations
concept power supply demonstrated ISL6160EVAL2 scaled across entire range 1.3V output voltage port power level. encompass this entire range there several component variables trade-offs consider. These variables trade-offs briefly discussed this document, more detailed extensive explanation please refer several listed documents [2], [4], page
Setting Output Voltage
Simple resistor value changes allow outputs 1.3V high input voltage. steady-state output voltage using following simple formula:
where
VOUT desired output voltage converter VREF HIP6006 internal reference voltage (typically 1.27V)
Input Capacitor Selection
HIP6006 input secondary rail) bypass capacitors control voltage overshoot across MOSFETs. small ceramic capacitors high frequency decoupling bulk capacitors supply current needed each time turns number input capacitors their capacitance usually determined their maximum current rating. conservative approach determine converter maximum input current, assume would have supplied from input capacitors. providing enough capacitors meet required current rating, usually provides enough capacitance proper power de-coupling.
Output Capacitor Selection
Output capacitors required filter output supply load transient current. filtering requirements function switching frequency ripple current. load transient requirements function slew rate (di/dt) magnitude transient load current. These requirements generally with capacitors careful layout. with input capacitors, number output capacitors determined parameter different than sheer capacitance. Based desired output ripple output transient response, maximum determined. Based design's dimensional restraints, optimum compromise between number size output capacitors reached. Conservative approaches dictate using data book's maximum values ESR; this design will still meet initial criteria even capacitor's active life. High frequency decoupling output implemented application provides high frequency decoupling components load output. applications requiring good high frequency decoupling,
MOSFET Selection Effect Efficiency
This section shows graphically that larger, lower RDSon) MOSFET does always improve converter efficiency. Figure shows that smaller RFP25N05 MOSFETs more efficient over most line load range than larger RFP45N06 MOSFETs. RFP25N05 rDS(ON) (maximum 25oC) versus RFP45N06. comparison RFP25N05,
Application Note AN9959
output should accordingly decoupled using ceramic capacitors. This measure especially necessary high output capacitors used. output load initially delivered from output capacitors. This finite amount time required inductor current slew level output current required load, results temporary (VLOW) output voltage, Figure Conversely, sudden removal same output load, energy stored inductor dumped into output capacitors, creating temporary hump (VHIGH) output voltage.
Output Inductor Selection
output inductor selected meet output voltage ripple requirements minimize converter's response time load transient. inductor value determines converter's ripple current ripple voltage function ripple current. Increasing value inductance reduces ripple current voltage. However, large inductance values reduce converter's response time load transient. parameters limiting converter's response load transient time required change inductor current from initial current value transient current level. During this interval difference between inductor current transient current level must supplied output capacitor. Minimizing response time minimize output capacitance required.
Conclusion
ISL6160EVAL2 board lends itself well evaluation complete single fixed voltage Class power supply providing conceptual platform your specific power control supply needs. addition, with availability multiple output voltage converters such IPM6220A coupled with ISL6160, Intersil provides application solution almost every InfiniBand module.
References
Intersil documents available web, http://www.intersil.com/ ISL6160 Data Sheet, Intersil Corporation, FN9028 HIP6006 Data Sheet, Intersil Corporation, FN4306. IPM6220A Data Sheet, Intersil Corporation, FN9032 Application Note, Intersil Corporation, AN9722. Application Note, Intersil Corporation, AN9761
Output Ripple Voltage
amount ripple voltage output DC-DC converter varies with, switching frequency, output inductor, output capacitors.
Output Load Transient Response
application sudden load requiring converter supply maximum output current, most energy required
Application Note AN9959
VB_IN (12V) 47µF VB_Ret VA_En VA_IN (5V) VA_In VA_Out VA_Ret VB_In ISL6160
0.01
1.4K GATE ISEN ISET VA_Fault
1000pF
CTIM VB_On DC-DC 0.1µF
100µF
1000pF VA_RET VB_RET
VBxEN_L Local (jumper)
470µF
1206
1206
MONITOR PROTECTION OCSET BOOT UGATE PHASE PVCC 33pF 1.6K COMP LGATE PGND 820µF VB_RET 0.1µF 5VOUT 1000pF 4.1K 4148
6.98K 0.1µF
HIP6006
0.001µF 1.6K SPARE
FIGURE ISL6160EVAL2 SCHEMATIC
Application Note AN9959 Bill Materials HIP6006EVAL1
PART ISL6160IB HIP6006CV SN74AHC1G86 equiv Si4922DY equiv ITF86130SK8T equiv 1N4148 10µH 1.4K 0.01 3.0K 6.98K 100µF 470µF 820µF 1000pF 47µF 0.1µF 33pF 0.001µF 1314353-00 EZM06DRXH DESCRIPTION InfiniBand Power Controller Synchronous Rectified Buck Controller Single gate Dual 30V, 0.018, N-Channel MOSFET 14A, 40V, 0.008, N-Channel MOSFET Rectifier, 100mA, Output Filter Inductor Current Resistor, 1/16W Current Sense Resistor, Resistor, 1/16W Resistor, 1/16W Resistor, 1/16W Resistor, 1/16W Resistor, 1/16W Resistor, 1/16W Resistor, 1/16W Through hole Resistor, Resistor, 1/10W Electrolytic Aluminum Capacitor, Electrolytic Aluminum Capacitor, Electrolytic Aluminum Capacitor, Ceramic Capacitor, Ceramic Capacitor, Ceramic Capacitor, Ceramic Capacitor, Ceramic Capacitor, Ceramic Capacitor, Local power enable Jumper Test Points Scope Probe Test Point Banana Jacks Edge Connector PACKAGE 14NSOIC 14TSSOP 5SOT-23 8SOIC 8SOIC DO35 Wound Toroid 0603 2512 0603 0603 0603 0603 0603 0603 0603 0805 Radial Radial Radial 0603 0603 0603 0603 0603 0603 C13, PWR_EN TP1- TP3, VOUT VENDOR INTERSIL INTERSIL Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Various Tektronics
Various VB_IN, VA_IN, VB_RET, VA_RET Sullins
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