LTC3704 LINER [Linear Technology], LTC3704 Datasheet
LTC3704
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LTC3704 Summary of contents
Page 1
... Burst Mode operation at light loads, a low minimum OSC operating supply voltage of 2.5V and a low shutdown ® Operation quiescent current make the LTC3704 ideally suited for battery-operated systems. For applications requiring constant frequency operation, >36V) the Burst Mode operation feature can be defeated using the MODE/SYNC pin ...
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... MODE/SYNC TH I Pin Load = 5 A (Note 5) TH Falling I Voltage (Note 5) TH Duty Cycle < 20 SENSE V = 30V SENSE U W ORDER PART NUMBER LTC3704EMS 10 SENSE INTV CC 7 GATE 6 GND MS PART MARKING = 120 C/ W LTYT MIN TYP MAX 2 ...
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... 3300pF (Note 7) L Note 5: The LTC3704 is tested in a feedback loop that servos V reference voltage with the I (the no load to full load operating voltage range for the I 1.23V). Note synchronized application, the internal slope compensation gain is increased by 25%. Synchronizing to a significantly higher ratio will ...
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... LTC3704 W U TYPICAL PERFOR A CE CHARACTERISTICS NFB Voltage vs Temp –1.25 –1.24 –1.23 –1.22 –1. –50 – 100 125 TEMPERATURE ( C) 3704 G01 Shutdown Mode (V) IN 3704 G04 Burst Mode I vs Temperature Q 500 400 ...
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... G14 INTV Line Regulation CC 5 5.3 5.2 5 (V) IN 3704 G17 LTC3704 R vs Frequency T 1000 100 10 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (kHz) 3704 G12 SENSE Pin Current vs Temperature 45 GATE HIGH V ...
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... LTC3704 CTIO S RUN (Pin 1): The RUN pin provides the user with an accurate means for sensing the input voltage and pro- gramming the start-up threshold for the converter. The falling RUN pin threshold is nominally 1.248V and the comparator has 100mV of hysteresis for noise immunity. ...
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... SLOPE COMPENSATION V-TO-I OSC I OSC 50k 200k + 0.30V EA – BURST COMPARATOR V-TO-I 1.230V LDO SLOPE 1.230V UV TO START-UP BIAS CONTROL V IN LTC3704 RUN + 1 BIAS AND C2 START-UP CONTROL – 1.248V 100mV HYSTERESIS V IN (1.348V RISING) 9 INTV CC GATE 7 LOGIC S Q GND R PWM LATCH SENSE + ...
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... RUN pin below 1.248V, the chip is off and the input V SW supply current is typically only 10 A. The LTC3704 can be used either by sensing the voltage drop across the power MOSFET or by connecting the SENSE pin to a conventional shunt resistor in the source SENSE of the power MOSFET, as shown in Figure 2 ...
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... 5A/DIV Figure 4. LTC3704 Low Output Current Operation with Burst Mode Operation Disabled (MODE/SYNC = INTV When an external clock signal drives the MODE/SYNC pin voltage rate faster than the chip’s internal oscillator, the oscillator will synchronize to it. In this synchronized mode, Burst Mode operation is disabled ...
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... INTV Regulator Bypassing and Operation internal, P-channel low dropout voltage regulator pro- duces the 5.2V supply which powers the gate driver and logic circuitry within the LTC3704, as shown in Figure 1/f O The INTV bypassed to ground immediately adjacent to the IC pins with a minimum of 4.7 F tantalum or ceramic capacitor. ...
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... U U APPLICATIO S I FOR ATIO cause the LTC3704 to exceed its maximum junction temperature rating. The junction temperature can be estimated using the following equations • Q Q(TOT • • • TH(JA) The total quiescent current I ...
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... LTC3704 U U APPLICATIO S I FOR ATIO The resistor R1 is typically chosen to be less than 1M. For applications where the RUN pin is only to be used as a logic input, the user should be aware of the 7V + INPUT SUPPLY OPTIONAL FILTER CAPACITOR – Figure 8a. Programming the Turn-On and Turn-Off Thresholds Using the RUN Pin ...
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... APPLICATIO S I FOR ATIO Applications Circuits A simple positive-to-negative application circuit for the LTC3704 is shown in Figure 1. The basic operation of this circuit is shown in Figure 9. During the on-time the inductor currents flow through the switch, and during the off-time these currents flow through the output diode. The ...
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... LTC3704 U U APPLICATIO S I FOR ATIO internal ramp compensation (at duty cycles above 50%), and the converter operation will approach voltage mode (ramp compensation reduces the gain of the current loop). If too small an inductor is used, but the converter is still operating in CCM (near critical conduction mode), the internal ramp compensation may be inadequate to prevent subharmonic oscillation ...
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... coupled Power MOSFET or Sense Resistor Selection L2(PEAK) If the maximum voltage on the drain of the power MOSFET (which is V 36V then the circuit can take advantage of the LTC3704’ SENSE 1 eliminate the sense resistor. For higher switch voltages • 1 – ...
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... LTC3704 U U APPLICATIO S I FOR ATIO 200 150 100 0.2 0.4 0.5 DUTY CYCLE Figure 11. Maximum SENSE Threshold Voltage vs Duty Cycle Another method of choosing which power MOSFET to use is to check the maximum output current for a given R , since MOSFET on-resistances are generally DS(ON) available in discrete values. ...
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... Depending upon the application, it may be that the ceramic capacitor alone will be sufficient. The RMS ripple current rating of the output capacitor needs to be greater than: LTC3704 500ns/DIV 3704 F13 , due to the ripple current of L2 (the – ...
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... LTC3704 U U APPLICATIO S I FOR ATIO 1 ( – MAX I • RMS COUT ( ) should be noted that these equations assume no cou- pling between the inductors. If the inductors are wound on the same core, the ripple currents at the input and output can be tuned to very low values, and so the equations above would be extremely conservative ...
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... Be sure to specify surge-tested capacitors! Burst Mode Operation and Considerations The choice of MOSFET R and inductor value also DS(ON) determines the load current at which the LTC3704 enters Burst Mode operation. When bursting, the controller clamps the peak inductor current to approximately ...
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... LTC3704 U U APPLICATIO S I FOR ATIO regulator feedback loop acts on the resulting error amp output signal to return V to its steady-state value. During O this recovery time, V can be monitored for overshoot or O ringing that would indicate a stability problem. A second, more severe transient can occur when connect- ing loads with large (> ...
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... C : TDK C5750X5R1C476M TDK C5750X7R1C476M TDK C5750X5R0J107M OUT TAIYO YUDEN LMK316BJ475ML VCC 10nF 1 10 3704 F16 Figure 17. Maximum Output Current vs Input Voltage LTC3704 D MAX – I • MAX ( ) – MAX 15V V OUT –5. • ...
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... LTC3704 U U APPLICATIO S I FOR ATIO V (AC) OUT 10mV/DIV I (DC) L2 1A/DIV 1 s/DIV –2V OUT Figure 18. Output Ripple Voltage and Inductor Current for the Circuit in Figure 15 V (AC) OUT 100mV/DIV 2A I (DC) OUT 1A/DIV 0.5A 250 s/DIV V = 15V IN Figure 20. Load Step Response at V for the Circuit in Figure 15 ...
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... U U APPLICATIO S I FOR ATIO PC Board Layout Checklist 1. In order to minimize switching noise and improve output load regulation, the GND pin of the LTC3704 should be connected directly to 1) the negative termi- nal of the INTV decoupling capacitor, 2) the negative CC terminal of the output decoupling capacitors, 3) the ...
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... LTC3704 is not shared with other converters. AC input current from another converter could cause substantial input voltage ripple, and this could interfere with the operation of the LTC3704. A few inches of PC trace or wire (L 100nH) between the C V should be sufficient to prevent current sharing IN problems ...
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... X5R R FB1 FB2 13.7k 1% Figure 24 Input, –8V at 1.2A Output Converter 4.5 5.0 3704 F25 Figure 26. Output Efficiency at 3V and 5V Input V (AC) OUT 100mV/DIV I (DC) OUT 0.5A/DIV 3704 F27 LTC3704 OUT –8.0V • • 1.2A to 2.5A L2 OUT 22 F 100 F X5R X5R D1 ...
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... LTC3704 U U APPLICATIO S I FOR ATIO 5.4V UV – 49.9k 150k 1nF C C2 100pF RUN I TH LTC3704 R C NFB 82k FREQ C C1 MODE/SYNC 1nF R T 120k f = 200kHz R R FB1 FB2 2.49k 45. 12V 220 F T1* 16V ...
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... BSC 4.88 0.10 DETAIL “A” (.192 .004) 0 – 6 TYP 0.53 0.01 (.021 .006) 1.10 (.043) DETAIL “A” MAX SEATING PLANE 0.17 – 0.27 (.007 – .011) LTC3704 0.497 0.076 (.0196 .003 REF 3.00 0.102 (.118 .004) NOTE 0.86 (.034) REF 0.13 0.05 (.005 .002) ...
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... McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 High Efficiency Positive-to-Negative Converter R4 154k 1% L1 RUN SENSE 25V X7R LTC3704 47 F 16V NFB INTV CC M1 FREQ GATE C VCC 4.7 F MODE/SYNC GND C : TDK C5570X5R1C476M D1: FAIRCHILD MBR2035CT TDK C5750X5R0J107M ...