500-kHz Half-Bridge DC/DC Controller with Integrated ...

1 vishay SiliconixSi9122 Document Number: 71815S-80038-Rev. J, is End of Life 12/2014500-kHz Half-Bridge DC/DC Controller with Integrated Secondary Synchronous Rectification DriversFEATURES 12 V to 72 V input voltage range Integrated Half-Bridge primary drivers(1 A drive capability) Secondary synchronous signals with programmable deadtime delay Voltage mode control Voltage feedforward compensation High voltage pre-regulator operates during start-up Current sensing on low-side primary device Frequency foldback eliminates constant current tail Advanced maximum current control during start-up andshorted load Low input voltage detection Programmable soft-start function Over temperature protectionsAPPLICATIONS Network cards Power supply modulesDESCRIPTIONSi9122 is a dedicated

2 Half-Bridge IC ideally suited to fixedtelecom applications where efficiency is required at lowoutput voltages ( < V). Designed to operate within thefixed telecom voltage range of 33 to 72 V, the IC is capableof controlling and driving both the low and high-sideswitching devices of a half bridge circuit and also controllingthe switching devices on the secondary side of the to the very low on-resistance of the secondaryMOSFETs, a significant increase in the efficiency can beachieved as compared with conventional Schottky of the secondary devices is by means of a pulsetransformer and a pair of inverters.

3 Such a system hasefficiencies well in excess of 90 % even for low outputvoltages. On-chip control of the dead time delays betweenthe primary and secondary synchronous signals keepefficiencies high and prevent accidental destruction of thepower transformer. An external resistor sets the switchingfrequency from 200 kHz to 625 has advanced current monitoring and controlcircuitry which allow the user to set the maximum current inthe primary circuit. Such a feature acts as protection againstoutput shorting and also provides constant current into largecapacitive loads during start-up or when paralleling powersupplies.

4 Current sensing is by means of a sense resistor onthe low-side primary BLOCK DIAGRAMF igure V to 72 VSynchronousRectifiersVCC-+VREFE rrorAmplifierOpto IsolatorVOUT+-1 V to 12 V Number: 71815S-80038-Rev. J, 14-Jan-08 vishay SiliconixSi9122 TECHNICAL DESCRIPTIONSi9122 is a voltage mode Controller for the half-bridgetopology. with 100 V depletion mode MOSFET capability,the Si9122 is capable of powering directly from the highvoltage bus to VCC through an external PNP pass transistor,or may be powered through an external regulator directlythrough the VCC pin.

5 with PWM control, Si9122 providespeak efficiency throughout the entire line and load range. Inorder to simplify the traditional secondary synchronousrectification, Si9122 provides intelligent gate drive signals tocontrol the secondary MOSFETs. with independent gatedrive signals from the Controller , transformer design is nolonger limited by the gate to a source rating of the provides constant VGS voltage, independent of linevoltage to minimize the gate charge loss as well asconduction loss. A break-before-make function is included toprevent shoot through current or transformer Break-Before-Make time is incorporated into theIC and is programmable by an external resistor is packaged in TSSOP-20 and MLP65-20 TSSOP-20 and MLP65-20 packages are available inlead (Pb)-free option.

6 In order to satisfy the stringent ambienttemperature requirements, Si9122 is rated to handle theindustrial temperature range of - 40 C to 85 C. When asituation arises which results in a rapid increase in primary(or secondary current) such as output shorted or start-upwith a large output capacitor, control of the PWM generatoris handed over to the current loop. Monitoring of the loadcurrent is by means of a sense resistor on the primary low-side BLOCK DIAGRAMF igure REF - + Pre-Regulator - + - + REG_COMP V INDET V REF V IN + - Error Amplifier 132 k EP - + PWM Comparator SS - + CS2 CS1 Over Current Protection GND V UVLO V UV V SD V CC Duty Cycle Control C L_CONT Driver Control and Timing BBM OTPOSCR OSC V FF Ramp SR L SR H PGNDD L D H SYNC Driver Low SYNC Driver High Low-Side Driver High-Side Primary Driver IntBST L X Si9122 Peak DET V REF 2 60 k I SS V 550 mV 20 A 8 V V V CC V CC V CC Document

7 Number: 71815S-80038-Rev. J, SiliconixSi9122 Notes: a. Device Mounted on JEDEC compliant 1S2P test Derate - 14 mW/ C above 25 Derate - 26 mW/ C above 25 beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operationof the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximumrating conditions for extended periods may affect device MAXIMUM RATINGS All voltages referenced to GND = 0 VParameter LimitUnit VIN (Continuous)75 VVIN (100 ms) Continuous90100 ms115 VLX75 VBST - VLX15 VREF, ROSC- to VCC + Inputs- to VCC + Inputs- to VCC + Pre-Regulator Input Current (Continuous)5mAStorage Temperature- 65 to 150 COperating Junction Temperature150 Power DissipationaTSSOP-20 MLP65-208502500mWThermal Impedance ( JA)

8 TSSOP-20bMLP65-20c7538 C/WRECOMMENDED OPERATING RANGE All voltages referenced to GND = 0 VParameter LimitUnit VIN 12 to 72 VCVIN1 || CVIN2100 F/ESR 100 m , FVCC Operating10 to FfOSC 200 to 600kHzROSC24 to 72k RBBM22 to 50 CBBMh> CLOAD150 Analog Inputs0 V to VCC - 2 VVDigital Inputs0 V to VCCR eference Voltage Output Current0 to Number: 71815S-80038-Rev. J, 14-Jan-08 vishay SiliconixSi9122 SPECIFICATIONSa Parameter Symbol Test Conditions Unless Otherwise Specified fNOM = 500 kHz, VIN = 72 V VINDET = V.

9 10 V VCC VLimits - 40 to 85 CUnit ( V)Output VoltageVREFVCC = 12 V, 25 C Load = 0 Circuit CurrentISREFVREF = 0 V- 50mALoad RegulationdVr/dirIREF = 0 to - mA- 30- 75mVPower Supply RejectionPSRRat 100 Hz60dBOscillatorAccuracy (1 % ROSC)ROSC = 30 k , fNOM = 500 kHz- 2020%Max FrequencyiFMAXROSC = k 500625750kHzFoldback FrequencydFFOBKfNOM = 500 kHz, VCS2 - VCS1 > 150 mV100 Error AmplifierInput Bias CurrentIBIASVEP = 0 V- 40- 15 AGainAV- Supply RejectionPSRRat 100 Hz60dBSlew sCurrent Sense AmplifierInput Voltage CM RangeVCMVCS1 - GND.

10 VCS2 - GND 150 mVInput Amplifier Amplifier BandwidthBW5 MHzInput Amplifier Offset VoltageVOS 5mVCL_CONT CurrentICL_CONTdVCS = 0120 AdVCS = 100 mV0dVCS = 170 mV> 2mALower Current Limit ThresholdVTLCLIPD = IPU - ICL_CONT = 0 See Figure 6100mVUpper Current Limit ThresholdVTHCLIPD > 2 mA150 HysteresisIPU < 500 A- 50CL_CONT Clamp LevelCL_CONT(min)IPU = 500 OperationDuty CycleeDMAXfOSC = 500 kHzVEP = 0 V909295%DMINVEP = V< 15 VCS2 - VCS1 > 150 mV3 Pre-RegulatorInput Voltage+ VINIIN = 10 A72 VInput Leakage CurrentILKGVIN = 72 V, VCC > VREG10 ARegulator Bias CurrentIREG1 VIN = 72 V, VINDET < VSD86200 IREG2 VIN = 72 V, VINDET > VREF814mARegulator_CompISOURCEVCC = 12 V- 29- 19- 9 AISINK5082110 Pre-Regulator Drive CapacilityISTARTVCC < VREG20mADocument Number: 71815S-80038-Rev.