ltc1709-85 Linear Technology Corporation, ltc1709-85 Datasheet
ltc1709-85
Related parts for ltc1709-85
ltc1709-85 Summary of contents
Page 1
... SW1 S BG1 PGND + SENSE1 – SENSE1 TG2 BOOST2 0. SW2 BG2 INTV SENSE2 – SENSE2 LTC1709-85 2-Phase, 5-Bit VID, U 1709- 2-phase, VID programmable, syn- ® operation for 28V 10 F 35V 4 0.002 1 H 0.002 V OUT 1.05V TO 1.825V 40A C + ...
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... LTC1709- ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V ).........................36V to – 0.3V IN Topside Driver Voltages (BOOST1,2) .........42V to – 0.3V Switch Voltage (SW1, 2) .............................36V to – – SENSE1 , SENSE2 , SENSE1 , – SENSE2 Voltages ................... (1.1)INTV + – EAIN EXTV , INTV ATTENIN, ATTENOUT, PGOOD, BIAS VID25mV– ...
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... Ramping Negative 3.3V BIAS (Note 8) = 3.3V BIAS = 3.3V BIAS V < VID25mV–VID3 < 7V BIAS V = 1.2V PLLFLTR PLLFLTR V 2.4V PLLFLTR f < f PLLIN OSC f > f PLLIN OSC LTC1709- unless otherwise noted. MIN TYP MAX UNITS 470 – 0.5 –1.2 A 1.0 1.5 1.9 V 4.1 4 – 85 – ...
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... T J dissipation P according to the following formula: D LTC1709EG-85 • Note 4: The LTC1709-85 is tested in a feedback loop that servos V specified voltage and measures the resultant TYPICAL PERFOR A CE CHARACTERISTICS Efficiency vs Load Current (3 Operating Modes) 100 Burst Mode 90 OPERATION 80 ...
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... Maximum Current Sense Threshold vs Duty Factor DUTY FACTOR (%) Maximum Current Sense Threshold vs Sense Common Mode Voltage 0.5 1 1.5 COMMON MODE VOLTAGE (V) LTC1709-85 INTV and EXTV Switch CC CC Voltage vs Temperature 5.05 INTV VOLTAGE CC 5.00 4.95 4.90 4.85 4.80 EXTV SWITCHOVER THRESHOLD CC 4.75 4. – 50 – ...
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... LTC1709- TYPICAL PERFOR A CE CHARACTERISTICS Load Regulation 0.0 FCB = 15V IN FIGURE 1 –0.1 –0.2 –0.3 –0 LOAD CURRENT (A) 170985 G13 Maximum Current Sense Threshold vs Temperature –50 – 125 100 TEMPERATURE ( C) 170985 G16 Load Step ...
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... EAIN (Pin 4): Input to the error amplifier that compares the feedback voltage to the internal 0.8V reference voltage. This pin is normally connected to a resistive divider from the output of the differential amplifier (DIFFOUT). pin voltage and TH + and SENSE pins in LTC1709-85 Oscillator Frequency vs Temperature 350 V = 2.4V PLLFLTR 300 250 ...
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... LTC1709- CTIO S PLLFLTR (Pin 5): The phase-locked loop’s lowpass filter is tied to this pin. Alternatively, this pin can be driven with voltage source to vary the frequency of the internal oscillator. PLLIN (Pin 6): External Synchronization Input to Phase Detector. This pin is internally terminated to SGND with 50k ...
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... FB SLOPE 45k 45k COMP 2. 1.2 A SHDN RUN RST SOFT 6V 4(V ) START FB 5-BIT VID DECODER TYPICAL ALL VID PINS 40k VID0 VID1 VID2 VID3 V BIAS LTC1709-85 INTV BOOST TOP D1 SW SWITCH INTV CC LOGIC BG BOT PGND R SENSE INTV CC + SENSE 30k – ...
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... U OPERATIO (Refer to Functional Diagram) Main Control Loop The LTC1709-85 uses a constant frequency, current mode step-down architecture with the two output stages oper- ating 180 degrees out of phase. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS latch, and turned off when the main current comparator resets the RS latch ...
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... RUN/SS capacitor during a severe overcurrent and/or short-circuit condition. Foldback current limiting is acti- vated when the output voltage falls below 70% of its nominal level whether or not the short-circuit latchoff – benefits regula- OUT circuit is enabled. LTC1709-85 170985f 11 ...
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... LTC1709- APPLICATIO S I FOR ATIO The basic LTC1709-85 application circuit is shown in Figure 1 on the first page. External component selection begins with the selection of the inductor(s) based on ripple current requirements and continues with the R resistor selection using the calculated peak SENSE1, 2 inductor current and/or maximum current limit ...
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... Power MOSFET, D1 and D2 Selection Two external power MOSFETs must be selected for each output stage with the LTC1709-85: one N-channel MOSFET for the top (main) switch, and one N-channel MOSFET for the bottom (synchronous) switch. The peak-to-peak drive levels are set by the INTV voltage ...
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... LTC1709- APPLICATIO S I FOR ATIO factors for the top and bottom MOSFETs of each output stage are given by: V OUT Main Switch Duty Cycle V IN Synchronous Switch Duty Cycle The MOSFET power dissipations at maximum output current are given by OUT ...
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... INTV Regulator CC /2 assuming: An internal P-channel low dropout regulator produces 5V at the INTV regulator powers the drivers and internal circuitry of the LTC1709-85. The INTV 50mA peak and must be bypassed to power ground with LTC1709-85 pin from the V supply pin. The INTV CC IN ...
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... If the input current does not change then the efficiency has not changed either. Output Voltage The LTC1709-85 has a true remote voltage sense capablity. The sensing connections should be returned from the load and INTV pins. ...
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... The output voltage is digitally programmed as defined in Table 1 using the VID25mV to VID3 logic input pins. The VID logic inputs program a precision, 0.25% internal feedback resistive divider. The LTC1709-85 has an output voltage range of 1.05V to 1.825V in 25mV steps. Between the ATTENOUT pin and ground is a variable resistor, R1, whose value is controlled by the five VID input pins (VID25mV to VID3) ...
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... IRAMP pulling the RUN/SS pin below 0.8V the LTC1709-85 is put into low current shutdown (I Q pins can be driven directly from logic as shown in Figure 5. Diode D1 in Figure 5 reduces the start delay but allows C to ramp up slowly providing the soft-start SS function. The RUN/SS pin has an internal 6V zener clamp (see Functional Diagram) ...
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... PLLIN W U Minimum On-Time Considerations Minimum on-time, t that the LTC1709-85 is capable of turning on the top C: MOSFET determined by internal timing delays and the gate charge required to turn on the top MOSFET. Low duty cycle applications may approach this minimum on-time limit and care should be taken to ensure that: ...
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... TH LTC1709- Figure 7. Active Voltage Positioning Applied to the LTC1709- Efficiency Considerations The percent efficiency of a switching regulator is equal to the output power divided by the input power times 100 often useful to analyze individual losses to determine what is limiting the efficiency and which change would produce the most improvement ...
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... A 50W supply will typically require a minimum of 200 F to 300 F of output capaci- tance having a maximum of 10m to 20m of ESR. The LTC1709-85 2-phase architecture typically halves the input and output capacitance requirements over compet- ing solutions. Other losses including Schottky conduc- tion losses during dead-time and inductor core losses generally account for less than 2% total additional loss ...
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... LTC1709- APPLICATIO S I FOR ATIO loop and is the filtered and compensated control loop response. The gain of the loop will be increased by increasing R and the bandwidth of the loop will be C increased by decreasing same factor that C is decreased, the zero frequency will ...
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... When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC1709-85. Check the following in your layout: 1) Are the signal and power grounds segregated? The LTC1709-85 signal ground pin should return to the (–) plate of C separately. The power ground returns to the OUT sources of the bottom N-channel MOSFETs, anodes of the Schottky diodes, and (– ...
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... LTC1709- APPLICATIO S I FOR ATIO pin (PGND) and the signal ground pin (SGND). This technique keeps inherent signals generated by high cur- rent pulses from taking alternate current paths that have finite impedances during the total period of the switching regulator. External OPTI-LOOP compensation allows over- compensation for PC layouts which are not optimized but this is not the recommended design procedure ...
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... APPLICATIO S I FOR ATIO BOLD LINES INDICATE HIGH, SWITCHING CURRENT LINES. KEEP LINES TO A MINIMUM LENGTH. Figure 8. Instantaneous Current Path Flow in a Multiple Phase Switching Regulator W U SW1 L1 R SENSE1 D1 SW2 L2 R SENSE2 D2 LTC1709-85 V OUT C OUT + 170985 F09 R L 170985f 25 ...
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... LTC1709- APPLICATIO S I FOR ATIO SINGLE PHASE CIN I COUT SW1 V SW2 CIN I COUT Figure 9. Single and 2-Phase Current Waveforms DUAL PHASE L1 L2 RIPPLE 170985 F10 170985f ...
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... Plastic SSOP (5.3mm) (Reference LTC DWG # 05-08-1640) 1.25 0. 5.3 – 5.7 0.65 BSC – 8 0.65 (.0256) BSC 0.22 – 0.38 (.009 – .015) LTC1709-85 12.50 – 13.10* (.492 – .516 7.40 – 8.20 (.291 – .323 ...
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... Intel Mobile VID Synchronous Step-Down Controller LTC3732 3-Phase Step-Down Synchronous Controller (VRM 9.0/9.1) Adaptive Power and No R are trademarks of Linear Technology Corporation. SENSE Linear Technology Corporation 28 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LTC1709-85 36 RUN/ SENSE1 TG1 34 – ...