Electronic Components Datasheet Search

Delete All
ON OFF
 ALLDATASHEET.COM Part No.DescriptionMarking X

ISL6336B Datasheet(PDF) 24 Page - Renesas Technology Corp

 Part No. ISL6336B Description 6-Phase PWM Controller with Light Load Efficiency Enhancement and Current Monitoring Download 32 Pages Scroll/Zoom 100% Manufacturer RENESAS [Renesas Technology Corp] Direct Link http://www.renesas.com Logo

ISL6336B Datasheet(HTML) 24 Page - Renesas Technology Corp

 24 / 32 pageISL6336BFN6696 Rev 3.00Page 24 of 32May 5, 2016Based on the VCC voltage, ISL6336B converts the TM pinvoltage to a 6-bit digital signal for temperature compensation.With the non-linear A/D converter of ISL6336B, the TM digitalsignal is linearly proportional to the NTC temperature. Foraccurate temperature compensation, the ratio of the TMvoltage to the NTC temperature of the practical design shouldbe similar to that in Figure 15.Depending on the location of the NTC and the air-flowing,the NTC may be cooler or hotter than the current sensecomponent. The TCOMP pin voltage can be utilized tocorrect the temperature difference between the NTC and thecurrent sense component. When a different NTC type ordifferent voltage divider is used for the TM function, theTCOMP voltage can also be used to compensate for thedifference between the recommended TM voltage curve inFigure 16 and that of the actual design. According to theVCC voltage, ISL6336B converts the TCOMP pin voltage toa 4-bit TCOMP digital signal as TCOMP factor N.TCOMP factor N is an integer between 0 and 15. Theintegrated temperature compensation function is disabled forN = 0. For N = 4, the NTC temperature is equal to thetemperature of the current sense component. For N < 4, theNTC is hotter than the current sense component. The NTC iscooler than the current sense component for N > 4. WhenN > 4, the larger TCOMP factor N, the larger the differencebetween the NTC temperature and the temperature of thecurrent-sense component.ISL6336B multiplexes the TCOMP factor N with the TM digitalsignal to obtain the adjustment gain to compensate thetemperature impact on the sensed channel current. Thecompensated channel current signal is used for droop andovercurrent protection functions.Design Procedure1. Properly choose the voltage divider for TM pin to matchthe TM voltage vs temperature curve with therecommended curve in Figure 15.2. Run the actual board under the full load and the desiredcooling condition.3. After the board reaches the thermal steady state, recordthe temperature (TCSC) of the current sense component(e.g., inductor) and the voltage at TM and VCC pins.4. Use Equation 23 to calculate the resistance of the TMNTC, and find out the corresponding NTC temperatureTNTC from the NTC datasheet.5. Use Equation 24 to calculate the TCOMP factor N:6. Choose an integral number close to the above result forthe TCOMP factor. If this factor is higher than 15, useN = 15. If it is less than 1, use N = 1.7. Choose the pull-up resistor RTC1 (typical 10k);8. If N = 15, do not need the pull-down resistor RTC2,otherwise obtain RTC2 by Equation 25:9. Run the actual board under full load again with the properresistors to TCOMP pin.10. Record the output voltage as V1 immediately after theoutput voltage is stable with the full load; Record theoutput voltage as V2 after the VR reaches the thermalsteady state.11. If the output voltage increases over 2mV as thetemperature increases, i.e. V2 - V1 >2mV, reduce N andredesign RTC2; if the output voltage decreases over 2mVas the temperature increases, i.e. V1 - V2 >2mV,increase N and redesign RTC2.A design spreadsheet is available to speed aid calculations.External Temperature CompensationBy pulling the TCOMP pin to GND, the integratedtemperature compensation function is disabled. In addition,one external temperature compensation network, shown inFigure 18, can be used to cancel the temperature impact onthe droop (i.e. load line).The sensed current will flow out of the FB pin and develop thedroop voltage across the resistor (RFB) between FB andVDIFF pins. If the RFB resistance reduces as the temperatureincreases, the temperature impact on the droop can becompensated. An NTC thermistor can be placed close to thepower stage and used to form RFB. Due to the non-lineartemperature characteristics of the NTC, a resistor network isneeded to make the equivalent resistance between FB andVDIFF pin reverse proportional to the temperature.The external temperature compensation network can onlycompensate the temperature impact on the droop, while ithas no impact to the sensed current inside ISL6336B.Therefore this network cannot compensate for thetemperature impact on the overcurrent protection function.RNTC TNTCVTMxRTM1VCC V–TM--------------------------------=(EQ. 23)N209x TCSC T–NTC3xTNTC 400+-------------------------------------------------------- 4+=(EQ. 24)RTC2NxRTC115 N–-----------------------=(EQ. 25)FIGURE 18. EXTERNAL TEMPERATURE COMPENSATIONVDIFFoCCOMPISL6336BINTERNALCIRCUITFB