ltc3891 Linear Technology Corporation, ltc3891 Datasheet
ltc3891
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ltc3891 Summary of contents
Page 1
... ESR values. The LTC3891 features a precision 0.8V reference and power good output indicator. A wide 4V to 60V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries. The output voltage of the LTC3891 can be programmed between 0.8V to 24V. or EXTV IN ...
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... Voltages ......................................... –0. PGOOD Voltage ............................................ –0. TRACK/SS Voltage ....................................... –0. Operating Junction Temperature Range (Notes 2, 3) LTC3891E, LTC3891I .......................... –40°C to 125°C LTC3891H .......................................... –40°C to 150°C LTC3891MP ....................................... –55°C to 150°C Maximum Junction Temperature (Notes 2, 3) LTC3891E, LTC3891I ......................................... 125°C LTC3891H, LTC3891MP .................................... 150° ...
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... V = 12V CONDITIONS (Note 4); I Voltage = 1.2V TH –40°C to 85°C LTC3891E, LTC3891I LTC3891H, LTC3891MP (Note 4) (Note 4 4.5V to 60V IN (Note 4) Measured in Servo Loop; ∆I Voltage = 1.2V to 0.7V TH (Note 4) Measured in Servo Loop; ...
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... LTC3891 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER Gate Driver TG Pull-Up On-Resistance Pull-Down On-Resistance BG Pull-Up On-Resistance Pull-Down On-Resistance Transition Time Rise Time f Fall Time Transition Time Rise Time f Fall Time TG/BG t Top Gate Off to Bottom Gate On Delay ...
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... OUTPUT CURRENT (A) FIGURE 12 CIRCUIT 3891 G01 Note 4: The LTC3891 is tested in a feedback loop that servos V specified voltage and measures the resultant V 85°C is not tested in production and is assured by design, characterization and correlation to production testing at other temperatures (125°C for the LTC3891E/LTC3891I, 150°C for the LTC3891H/LTC3891MP). For the LTC3891MP , the specification at – ...
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... LTC3891 TYPICAL PERFORMANCE CHARACTERISTICS Load Step Burst Mode Operation V OUT 100mV/DIV AC- COUPLED I L 2A/DIV 3891 G04 50µs/DIV LOAD STEP = 100mA 12V 3.3V OUT FIGURE 12 CIRCUIT Inductor Current at Light Load FORCED CONTINUOUS MODE Burst Mode OPERATION 1A/DIV PULSE-SKIPPING MODE 5µs/DIV ...
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... TEMPERATURE (°C) Shutdown (RUN) Threshold vs Temperature 1.30 1.25 RUN RISING 1.20 RUN FALLING 1.15 1.10 –75 –50 – 100 TEMPERATURE (°C) LTC3891 Maximum Current Sense Threshold vs Duty Cycle FLOAT LIM INTV LIM GND LIM ...
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... LTC3891 TYPICAL PERFORMANCE CHARACTERISTICS – SENSE Pin Input Bias Current vs Temperature 800 700 V > INTV + 0.5V OUT CC 600 500 400 300 200 100 V < INTV – 0.5V OUT CC 0 –100 –50 –25 75 100 125 150 – TEMPERATURE (°C) 3891 G22 Undervoltage Lockout Threshold vs Temperature 4 ...
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... When not synchronizing to an external clock, this input determines how the LTC3891 operates at light loads. Pull- ing this pin to ground selects Burst Mode operation. An internal 100k resistor to ground also invokes Burst Mode operation when the pin is floated ...
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... A capacitor to ground at this pin sets the ramp time to final regulated output voltage. Alternatively, a resistor divider on another voltage supply connected to this pin allows the LTC3891 output to track another supply during start-up. FUNCTIONAL DIAGRAM PGOOD ...
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... C to recharge. Shutdown and Start-Up (RUN, TRACK/SS Pins) The LTC3891 can be shut down using the RUN pin. Pulling this pin below 1.16V shuts down the main control loop. Pulling the RUN pin below 0.7V disables the controller and most internal circuits, including the INTV In this state, the LTC3891 draws only 14μ ...
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... Light Load Current Operation (Burst Mode Operation, Pulse-Skipping or Forced Continuous Mode) (PLLIN/MODE Pin) The LTC3891 can be enabled to enter high efficiency Burst Mode operation, constant frequency pulse-skipping mode, or forced continuous conduction mode at low load cur- rents. To select Burst Mode operation, tie the PLLIN/MODE pin to SGND ...
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... The typical capture range of the phase-locked loop is from approximately 55kHz to 900kHz, with a guarantee to be between 75kHz and 750kHz. In other words, the LTC3891’s PLL is guaranteed to lock to an external clock source whose frequency is between 75kHz and 750kHz. ...
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... LTC3891 APPLICATIONS INFORMATION The Typical Application on the first page is a basic LTC3891 application circuit. LTC3891 can be configured to use either DCR (inductor resistance) sensing or low value resistor sensing. The choice between the two current sensing schemes is largely a design trade-off between cost, power consumption and accuracy. DCR sensing ...
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... Inductor DCR Sensing For applications requiring the highest possible efficiency at high load currents, the LTC3891 is capable of sensing the voltage drop across the inductor DCR, as shown in Figure 2b. The DCR of the inductor represents the small amount of DC resistance of the copper wire, which can be less than 1mΩ ...
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... LTC3891 APPLICATIONS INFORMATION The equivalent resistance scaled to the tem- perature inductance and maximum DCR DCR at 20°C • C1 The sense resistor values are: R1|| R2 R1• R1 1– The maximum power loss related to duty cycle, and will occur in continuous mode at the maximum input ...
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... Power MOSFET and Schottky Diode (Optional) Selection Two external power MOSFETs must be selected for the LTC3891 controller: 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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... I OUT RMS RUN Pin The LTC3891 is enabled using the RUN pin. It has a rising threshold of 1.21V with 50mV of hysteresis. Pulling the RUN pin below 1.16V shuts down the main control loop. Pulling it below 0.7V disables the controller and most internal circuits, including the INTV the LTC3891 draws only 14μ ...
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... Tracking and Soft-Start (TRACK/SS Pin) The start- controlled by the voltage on the OUT TRACK/SS pin. When the voltage on the TRACK/SS pin is less than the internal 0.8V reference, the LTC3891 regulates the V pin voltage to the voltage on the TRACK/SS pin FB instead of 0.8V. The TRACK/SS pin can be used to program an external soft-start function or to allow V another supply during start-up ...
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... INTV is regulated to 5.1V. CC supply pin or the IN Using the EXTV CC power to be derived from one of the LTC3891’s switching LDO and the EXTV regulator outputs (4.7V ≤ operation and from the V regulation (e.g., start-up, short-circuit). If more current is required through the EXTV external Schottky diode can be added between the EXTV ...
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... If there is no change in input current, then there is no change in efficiency. Fault Conditions: Current Limit and Current Foldback The LTC3891 includes current foldback to help limit load current when the output is shorted to ground. If the output ...
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... DC Voltage Any of the Above External Clock Minimum On-Time Considerations Minimum on-time the smallest time duration ON(MIN) that the LTC3891 is capable of turning on the top MOSFET determined by internal timing delays and the gate 3891 F09 FREQUENCY 350kHz 535kHz 50kHz to 900kHz Phase Locked to ...
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... The output voltage will continue to be regulated, but the ripple voltage and current will increase. The minimum on-time for the LTC3891 is approximately 95ns. However, as the peak sense voltage decreases the minimum on-time gradually increases up to about 130ns. ...
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... LTC3891 APPLICATIONS INFORMATION Other hidden losses such as copper trace and internal battery resistances can account for an additional 5% to 10% efficiency degradation in portable systems very important to include these system level losses during the design phase. The internal battery and fuse resistance losses can be minimized by making sure that ...
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... Schottky loop described above. 2. Does the LTC3891 V the (+) terminal of C connected between the (+) terminal of C ground. The feedback resistor connections should not be along the high current input feeds from the input capacitor(s) ...
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... Keep the SW, TG, and BOOST nodes away from sensitive small-signal nodes. All of these nodes have very large and fast moving signals and therefore should be kept on the output side of the LTC3891 and occupy minimum PC trace area. 6. Use a modified star ground technique: a low impedance, ...
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... CC INTVCC INTV SGND CC BG RUN – SENSE M1 C1* BOOST + SENSE OUT PGOOD ITH Figure 11. Branch Current Waveforms LTC3891 GND 1µF C CERAMIC OUT M2 D1* R SENSE PULL-UP PGOOD 3891 F10 V SENSE OUT C R OUT L1 3891 F11 ...
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... TO 60V C IN 22µF 100k INTV CC 41.2k 2200pF 10k 100pF 0.1µF MTOP, MBOT: Si7850DP L1 COILCRAFT SER1360-472KL C : SANYO 6TPE470M OUT D1: DFLS1100 28 V INTV IN CC LTC3891 2.2µF PGOOD PGND RUN I D1 LIM EXTV TG CC 0.1µF BOOST PLLIN/MODE SW FREQ BG ITH + SENSE 1nF TRACK/SS – SENSE ...
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... RUN I D1 LIM EXTV TG CC 0.1µF BOOST PLLIN/MODE SW FREQ BG ITH + SENSE 1nF TRACK/SS – SENSE SGND V FB SGND Figure 13. High Efficiency 12V Step-Down Converter LTC3891 MTOP L1 R SENSE 8µ OUT 12V C OUT 3A MBOT 180µF 100k 6.98k 3891 F13 3891f 29 ...
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... LTC3891 PACKAGE DESCRIPTION 3.50 ± 0.05 2.10 ± 0.05 1.50 REF 1.65 ± 0.05 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED PIN 1 TOP MARK (NOTE 6) 4.00 ± 0.10 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4 ...
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... BSC (.0077 – .0118) 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT MILLIMETERS (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE LTC3891 6.40 – 6.60* (.252 – .260) 3.86 (.152 6.40 2.74 (.252) ( ...
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... LTC3859 Q DC/DC Controller Low I , Single Output Step-Down Controller, 100% LTC3824 Q Duty Cycle 32 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● V INTV IN CC LTC3891 2.2µF PGOOD PGND RUN I D1 LIM EXTV TG CC 0.1µF BOOST PLLIN/MODE SW FREQ BG ITH ...