LTC3775 Linear Technology, LTC3775 Datasheet
LTC3775
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LTC3775 Summary of contents
Page 1
... TG 0.1μF 0.36μH V OUT SW 1.2V 470μF 15A BG 2.5V 2 PGND 3775 TA01a LTC3775 High Frequency Voltage Mode DC/DC Controller ® 3775 is a high effi ciency synchronous step-down current sensing maximizes effi ciency. DS(ON) Effi ciency and Power Loss vs Load Current 100 V = 12V 1.2V ...
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... LTC3775EUD#PBF LTC3775EUD#TRPBF LTC3775IUD#PBF LTC3775IUD#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: For more information on tape and reel specifi ...
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... Sinking (Note -SENSE 0.1V IN ILIMT = 0.5V ILIMB 7.5V < V < 38V IN ΔI = 0mA to 20mA INTVCC – 20mA IN INTVCC INTVCC INTV Rising CC Hysteresis LTC3775 = 5V, unless otherwise specifi ed. MIN TYP MAX l 4.5 38 3.5 14 1.19 1.22 1.25 0.74 140 –1 –4 0.597 0.600 0.603 l 0.5955 0.6045 ±0.01 0.01 0.1 –50 50 – ...
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... Note 7: Rise and fall times are measured using 10% and 90% levels. Delay and nonoverlap times are measured using 50% levels Note 8: The LTC3775 leading edge modulation architecture does not have a minimum TG pulse width requirement. The TG minimum pulse width is limited by the SW node rise and fall times. MIN ...
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... I L 10A/DIV I LOAD 10A/DIV 3775 G07 V = 12V 5μs/DIV 1.2V OUT LOAD STEP = 10A TO 0A MODE/SYNC = 0V SW FREQ = 500kHz FIRST PAGE CIRCUIT LTC3775 Load Regulation 1.206 V = 12V IN SW FREQ = 500kHz 1.204 FIRST PAGE CIRCUIT 1.202 1.200 1.198 1.196 1.194 ...
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... LTC3775 TYPICAL PERFORMANCE CHARACTERISTICS Pulse-Skipping Mode Waveform with 0.1A Load V OUT(AC) 100mV/DIV I L 2A/DIV V SW 10V/DIV V = 12V 5μs/DIV 1.2V OUT LOAD = 0.1A MODE/SYNC = INTV CC SW FREQ = 500kHz FIRST PAGE CIRCUIT Duty Cycle vs V COMP 100 12V V = 24V 40V ...
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... INTV (V) CC 3775 G18 T = 25° 3775 G21 3775 G23 20ns/DIV LTC3775 INTV Load Regulation –0.1 –0.2 –0.3 –0.4 –0.5 –0.6 –0.7 –0.8 –0.9 –1 5.6 6.0 INTV LOAD CURRENT (mA) CC 3775 G19 INTV Dropout vs Temperature ...
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... CC below 14μA. This pin has an internal 1μA pull-up current that allows the LTC3775 to power up if this pin is left fl oating. PGND (Pin 17): Power Ground (Exposed Pad). The BG driver returns to this pin. Connect PGND to the source of the bottom power MOSFET and the V capacitors ...
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... REF + 1.22V CHIP UVLO SHUTDOWN – INTV CC + 3.6V OVERTEMP EXT SYNC OSC MODE INTV – EA LINE + FEEDFORWARD PWM – + 0.66V MAX LTC3775 C VCC INTV IN CC INTV CC 0.6V 100μA R ILIMT I LIMT CTLIM + SENSE – R ILIMB I LIMB INTV CC CBLIM + PGND 10μA – V ...
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... N-channel MOSFETs. For circuit operation, please refer to the Block Diagram. The LTC3775 uses voltage mode control in which the duty cycle is controlled directly by the error amplifi er output. The error amplifi er adjusts the voltage at the COMP pin by comparing the V pin with the 0 ...
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... Stability also may depend on circuit board layout. To verify the calculated component values, all new circuit designs should be prototyped and tested for stability. V OUT REF ) LTC3775 ) 2 2 ⎛ ⎞ ⎛ ⎞ – ...
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... MOSFET is turned off and the bottom MOSFET is turned on until the overvoltage condition is cleared. Run/Shutdown The LTC3775 can be put into a low power shutdown mode with quiescent current <14μA by pulling the RUN/SHDN pin below 0.74V. The RUN/SHDN pin can also be used as an accurate external UVLO (undervoltage lockout) input with a threshold of 1.22V. The driver outputs stay low if this pin is < ...
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... SS voltage catches up with V , after which V OUT the SS ramp. The LTC3775 reverts to the selected mode once SS > 0.54V. Constant Switching Frequency The internal oscillator can be programmed from 250kHz to 1MHz with an external resistor from the FREQ pin to ground, in order to optimize component size, effi ...
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... The LTC3775 control loop is capable of operation with a TG on-time as low as 30ns sense resistor is employed on the top side, the LTC3775 automatically lowers the CTLIM blanking time from 200ns to 100ns. The CBLIM blanking time remains at 200ns. The ...
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... LIMT F current limit comparator, CBLIM. This voltage must be quiet. Connect R near the LTC3775 SGND pin. The other input of CBLIM is connected to the SW pin. The SW pin is also shared with ILIMT the bottom gate driver and should be connected near the drain of the bottom MOSFET, Q ...
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... If the INTV threshold of 3.1V, the gate drive outputs remain low. Thermal Considerations The LTC3775 is offered in a 3mm × 3mm QFN package (UD16) that has a thermal resistance R The UD16 package has a lead pitch of 0.5mm. The regulator can supply up to 50mA of gate drive load cur- rent ...
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... Operation at Low Supply Voltage CC The LTC3775 has a minimum input voltage of 4.5V. The gate driver for the LTC3775 consists of a PMOS pull-up and an NMOS pull-down device, allowing the full INTV voltage to be applied to the gates during power MOSFET switching. Nonetheless, care should be taken to deter- mine the minimum gate drive supply voltage (INTV order to choose the optimum power MOSFETs ...
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... For TG on-times smaller than the topside blanking times, the LTC3775 relies on the bottom current limit comparator, CBLIM, to monitor the inductor current. If CBLIM trips, the LTC3775 starts to skip pulses and at the same time pulls down the soft-start capacitor to limit the duty cycle can increase enough to turn on CTLIM and limit the peak inductor current ...
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... APPLICATIONS INFORMATION High Duty Cycle Operation The maximum duty cycle is limited by the LTC3775 internal oscillator reset time, the propagation delay of the PWM comparator and the BOOST pin supply refresh rate. The minimum off-time is typically 300ns. The top MOSFET driver is biased from the fl oating bootstrap ...
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... DS(ON) The gate drive voltage is set by the 5.2V INTV Consequently, logic-level threshold MOSFETs must be used in LTC3775 applications. If the INTV expected to drop below 5V, then sub-logic level threshold MOSFETs should be considered. Pay close attention to the V specifi cation because most logic-level MOSFETs (BR)DSS are limited to 30V or less ...
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... ESR and high bulk capacitance. Output Capacitor Selection The selection of C required to minimize voltage ripple and load step transients. The output ripple ΔV Δ ≤ Δ ESR OUT L where ΔI is the inductor ripple current. L LTC3775 ( ) V V – V OUT IN OUT ) ...
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... Sprague 595D series. Consult the manufacturer for other specifi c recommendations. Inductor Selection The inductor in a typical LTC3775 application circuit is chosen based on the required ripple current, its size and its saturation current rating. The inductor should not be al- lowed to saturate below the hard current limit threshold. ...
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... Thermal characterization can be done by placing a thermocouple in intimate contact with the winding/core structure burying the thermocouple within the windings themselves. R ILIMB ) LTC3775 = I pin maximum pull-down current of LIMT = I pin maximum pull-up current of LIMB and R ...
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... FB node short. 7. For applications with multiple switching power convert- ers connected to the same input supply, make sure that the input fi lter capacitor for the LTC3775 is not shared with other converters. AC input current from another converter could cause substantial input voltage ...
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... APPLICATIONS INFORMATION ripple, and this could interfere with the operation of the LTC3775. A few inches of PC trace or wire (L ≅ 100nH) between C of the LTC3775 and the actual source V IN should be suffi cient to prevent input noise interference problems. 8. The top current limit programming resistor, R ...
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... V . DS(ON) IN Next, verify the maximum duty cycle which occurs at minimum Maximum Duty Cycle 5 V This is below the LTC3775 maximum duty cycle of 90%. Next, calculate R to give the 500kHz operating SET frequency: 19500 = = SET 500 www.DataSheet4U.com Next, choose the inductor value for about 40% ripple ...
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... The ripple voltage will be OUT RIPPLE ( = 5V and IN(MIN) ) However 15A load step will cause an output volt age change of at least: ΔV OUT(STEP) LTC3775 ⎛ 0 005 . • ⎝ ⎝ ⎜ 500 • kHz • 470 = (15A)(0.0025Ω ...
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... C F 220pF ILIMT 732Ω LIMT R ILIMB 57.6k I SENSE LIMB C C VCC B 4.7μF 0.1μF INTV BOOST 0.01μF LTC3775 SET 39.2k FREQ BG FB PGND C2 330pF MODE/SYNC COMP RUN/SHDN SGND R B 10k R2 C1 4.7k 3.9nF 26V C IN1 R SENSE 330μF 0.003Ω ...
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... Load Step 5 V OUT(AC) 4 100mV/DIV 10A/DIV 12V 50μs/DIV 2.5V OUT LOAD = 0A TO 10A TO 0A 3775 TA03b MODE = 0V SW FREQ = 500kHz LTC3775 36V C IN1 ILIMT 330μF 35V SENSE 0.003Ω 220pF 1.2μH V OUT 2. OUT 10A 330μ ...
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... Input, 12V/5A Output at 500kHz 69.8k R ILIMT 1.24k LIMT 10k R ILIMB 56.2k I SENSE LIMB C VCC 4.7μF INTV BOOST 0.01μF LTC3775 SET 39.2k FREQ BG RUN/SHDN FB PGND C2 330pF MODE/SYNC COMP SGND 191k 10k R2 C1 7.68k 3.3nF Load Step 2.5 2.0 V ...
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... Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 0.75 0.05 3.00 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) 1.45 0.10 (4-SIDES) 0.200 REF 0.00 – 0.05 LTC3775 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP R = 0.115 OR 0.25 45 CHAMFER TYP 15 16 0.40 0. (UD16) QFN 0904 0.25 0.05 0.50 BSC 3775f 31 ...
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... LTC3775 RELATED PARTS PART NUMBER DESCRIPTION LTC3854 Small Footprint Wide V IN DC/DC Controller LTC3851A ™ Wide V Range Synchronous Step-Down SENSE IN LTC3851A-1 DC/DC Controller LTC3878 No R Constant On-Time Synchronous Step-Down SENSE DC/DC Controller LTC3879 No R Constant On-Time Synchronous Step-Down SENSE DC/DC Controller LTC3703-5 High Voltage Synchronous Step-Down DC/DC Voltage ...