www.irf.com Page 1 Data Sheet No. PD60293 IRS254(0,1)(S)PbFLED BUCK REGULATOR CONTROL ICDescription The IRS254(0,1) are high voltage, high frequency buck control ICs for constant LED current regulation. They incorporate a continuous mode time-delayed hysteretic buck regulator to directly control the average load current, using an accurate on-chip bandgap voltage reference. The application is inherently protected against short circuit conditions, with the ability to easily add open-circuit protection. An external high-side bootstrap circuit drives the buck switching element at high frequencies. A low-side driver is also provided for synchronous rectifier designs. All functions are realized within a simple 8 pin DIP or SOIC package. Typical Application Diagram Features 200 V (IRS2540) and 600 V (IRS2541) half bridge driver Micropower startup (VENTH+IQCCQuiescent VCCsupply current - 1.0 2.0 IFB= 1 V ICC50kVCCsupply current, f = 50 kHz - 2.0 3.0 mA Duty Cycle = 50% f = 50 kHzVCLAMPVCCzener clamp voltage 14.6 15.6 16.6 V ICC= 10 mA Floating Supply CharacteristicsIQBS0Quiescent VBSsupply current - 1.0 2.0 VHO= VSIQBS1Quiescent VBSsupply current - 2.0 3.0 mA IFB= 0 V VBSUV+VBSsupply undervoltage positive going threshold 6.5 7.5 8.5 VBSUV-VBSsupply undervoltage negative going threshold 6.0 7.0 8.0 V ILKOffset supply leakage current - 1 50 A IRS2540:VB=VS=200 V IRS2541:VB=VS=600 VCurrent Control OperationVENNTH+ENN pin positive threshold 2.5 2.7 3.0 VENNTH-ENN pin negative threshold 1.7 2.0 2.3 V V0.50.5 V voltage reference (die level test) 490 500 510 VIFBTHIFB pin threshold 455 500 540 mV f Maximum frequency - 500 - kHz Gate Driver Output CharacteristicsVOLLow level output voltage (HO or LO) - COM - VHLHigh level output voltage (HO or LO) - VCC- V trTurn-on rise time - 50 120 tfTurn-off fall time - 30 50 ns IO+/-Output source/sink short circuit pulsed current - 0.5/0.7 - A DT Deadtime - 140 - tLO,ONDelay between VIFBVIFBTHand LO turn-on - 320 - tLO,OFFDelay between VIFBVIFBTHand HO turn-off - 180 - ns IFB= 50 kHz square wave, 200 mV pk-pk DC offset = 400 mV Duty Cycle = 50% IRS254(0,1)(S)PbFwww.irf.com Page 5 Electrical Characteristics VCC= VBS= VBIAS= 14 V +/- 0.25 V, CLO=CHO=1000 pF, CVCC=CVBS=0.1 F, TA=25 C unless otherwise specified. Symbol Definition Min Typ Max Units Test Conditions Functional Block Diagram Values in block diagram are typical values Lead Assignment Pin Assignments Pin # Symbol Description1234IRS254(0,1)VCCCOMENN LOVSHOVB8765IFB1376542IFBVCCHOVSLOCurrent feedbackHigh-side floating returnHigh-side gate driver output8COMVB High-side gate driver floating supplyIC power & signal groundSupply voltageENN Disable outputs (LO=High, HO=Low)Low-side gate driver outputWatchdog timertWDWatchdog timer period - 20 - PWWDLO pulse width - 1.0 - s IFB=1 V LEVELSHIFTPULSEFILTER &LATCH786 VSHOVB152COMLOVCC15.6 V4ENN2 V3IFBDELAYDELAYUVLOUVN0. 5 VWatchdogTimer20 S1 S PulseGeneratorBANDGAPREFERENCE100 K IRS254(0,1)(S)PbFwww.irf.com Page 6 STATE DIAGRAM IRS254(0,1)(S)PbFwww.irf.com Page 7 Functional Description Operating Mode The IRS254(0,1) operates as a time-delayed hysteritic buck controller. During normal operating conditions the output current is regulated via the IFB pin voltage (nominal value of 500 mV). This feedback is compared to an internal high precision bandgap voltage reference. An on-board dV/dt filter has also been used to ignore erroneous transitioning. Once the supply to the IC reaches VCCUV+, the LO output is held high and the HO output low for a predetermined period of time. This initiates charging of the bootstrap capacitor, establishing the VBSfloating supply for the high-side output. The IC then begins toggling HO and LO outputs as needed to regulate the current. Fig.1 IRS254(0,1) Control Signals, Iavg=1.2 A As long as VIFBis below VIFBTH, HO is on, modulated by the watchdog timer described below, the load is receiving current from VBUS, which simultaneously stores energy in the inductor, as VIFBincreases, unless the load is open. Once VIFBcrosses VIFBTH, the control loop switches HO off after the delay tHO,OFF. Once HO is off, LO will turn on after the deadti