LTC3835IUFD#TRPBF Linear Technology, LTC3835IUFD#TRPBF Datasheet

Page 1

... PART # LTC3835 LTC3835-1 L, LT, LTC, LTM, Burst Mode, PolyPhase, OPTI-LOOP , Linear Technology and the Linear logo are registered trademarks and No R All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5408150, 5481178, 5705919, 5929620, 6304066, 6498466, 6580258, 6611131. ...

Page 2

LTC3835 ABSOLUTE MAXIMUM RATINGS Input Supply Voltage (V ) ......................... 36V to –0.3V IN Top Side Driver Voltage (BOOST) ............... 42V to –0.3V Switch Voltage (SW) ..................................... 36V to –5V INTV , (BOOST-SW), CLKOUT, PGOOD ... 8.5V to –0.3V CC ...

Page 3

... ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LTC3835EFE#PBF LTC3835EFE#TRPBF LTC3835IFE#PBF LTC3835IFE#TRPBF LTC3835EUFD#PBF LTC3835EUFD#TRPBF LTC3835IUFD#PBF LTC3835IUFD#TRPBF LEAD BASED FINISH TAPE AND REEL LTC3835EFE LTC3835EFE#TR LTC3835IFE LTC3835IFE#TR LTC3835EUFD LTC3835EUFD#TR LTC3835IUFD LTC3835IUFD#TR Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. ...

Page 4

LTC3835 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER TG/BG t Top Gate Off to Bottom Gate On Delay 1D Synchronous Switch-On Delay Time BG/TG t Bottom Gate Off to Top Gate On Delay 2D Top Switch-On ...

Page 5

TYPICAL PERFORMANCE CHARACTERISTICS Efficiency and Power Loss vs Output Current 100 Burst Mode OPERATION FORCED CONTINUOUS MODE 90 PULSE SKIPPING MODE 12V 3.3V OUT 0.001 0.01 ...

Page 6

LTC3835 TYPICAL PERFORMANCE CHARACTERISTICS Total Input Supply Current vs Input Voltage 350 300 250 300µA LOAD 200 150 NO LOAD 100 INPUT VOLTAGE (V) 3835 G10 Maximum Current Sense Voltage vs I ...

Page 7

TYPICAL PERFORMANCE CHARACTERISTICS TRACK/SS Pull-Up Current vs Temperature 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 –45 –30 – TEMPERATURE (°C) 3835 G19 Sense Pins Total Input Current vs Temperature 200 V = ...

Page 8

LTC3835 PIN FUNCTIONS (FE Package/UFD Package) CLKOUT (Pin 1/Pin 19): Open-Drain Output Clock Signal available to daisychain other controller ICs for additional MOSFET driver stages/phases. PLLLPF (Pin 2/Pin 20): The phase-locked loop’s lowpass filter is tied to this pin when ...

Page 9

PIN FUNCTIONS (FE Package/UFD Package) Tying this pin to INTV forces continuous inductor current CC operation. Tying this pin to a voltage greater than 0.9V and less than INTV selects pulse-skipping operation. CC FUNCTIONAL DIAGRAM PLLIN/ MODE F PHASE DET ...

Page 10

LTC3835 OPERATION (Refer to Functional Diagram) Main Control Loop The LTC3835 uses a constant-frequency, current mode step-down architecture. During normal operation, the external top MOSFET is turned on when the clock sets the RS latch, and is turned off when ...

Page 11

OPERATION (Refer to Functional Diagram) Light Load Current Operation (Burst Mode Operation, Pulse-Skipping, or Continuous Conduction) (PLLIN/MODE Pin) The LTC3835 can be enabled to enter high efficiency Burst Mode operation, constant-frequency pulse-skipping mode, or forced continuous conduction mode at low ...

Page 12

LTC3835 OPERATION (Refer to Functional Diagram) The typical capture range of the LTC3835’s phase-locked loop is from approximately 115kHz to 800kHz, with a guarantee to be between 140kHz and 650kHz. In other words, the LTC3835’s PLL is guaranteed to lock ...

Page 13

APPLICATIONS INFORMATION R Selection For Output Current SENSE R is chosen based on the required output current. SENSE The current comparator has a maximum threshold of 100mV/R and an input common mode range of SENSE SGND to 10V. The current ...

Page 14

LTC3835 APPLICATIONS INFORMATION inductance collapses abruptly when the peak design current is exceeded. This results in an abrupt increase in inductor ripple current and consequent output voltage ripple. Do not allow the core to saturate! Power MOSFET and Schottky Diode ...

Page 15

APPLICATIONS INFORMATION C and C Selection IN OUT In continuous mode, the source current of the top MOSFET is a square wave of duty cycle (V OUT large voltage transients, a low ESR capacitor sized for the maximum RMS current ...

Page 16

LTC3835 APPLICATIONS INFORMATION 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 LTC3835 regulates the ...

Page 17

APPLICATIONS INFORMATION INTVCC Regulators The LTC3835 features two separate internal P-channel low dropout linear regulators (LDO) that supply power at the INTV pin from either the V supply pin or the EXTV CC IN pin, respectively, depending on the connection ...

Page 18

LTC3835 APPLICATIONS INFORMATION 4. EXTV Connected to an Output-Derived Boost Network. CC For 3.3V and other low voltage regulators, efficiency gains can still be realized by connecting EXTV output-derived voltage that has been boosted to greater than 4.7V. This can ...

Page 19

APPLICATIONS INFORMATION Phase-Locked Loop and Frequency Synchronization The LTC3835 has a phase-locked loop (PLL) comprised of an internal voltage-controlled oscillator (VCO) and a phase detector. This allows the turn-on of the top MOSFET (TG locked to the rising ...

Page 20

LTC3835 APPLICATIONS INFORMATION Minimum On-Time Considerations Minimum on-time t is the smallest time duration ON(MIN) that the LTC3835 is capable of turning on the top MOSFET determined by internal timing delays and the gate charge required to turn ...

Page 21

APPLICATIONS INFORMATION a 5V output 20% loss for a 3.3V output. Efficiency varies as the inverse square of V same external components and output power level. The combined effects of increasingly lower output voltages and higher ...

Page 22

LTC3835 APPLICATIONS INFORMATION most critical frequency range of the feedback loop. The output voltage settling behavior is related to the stability of the closed-loop system and will demonstrate the actual overall supply performance. A second, more severe transient is caused ...

Page 23

APPLICATIONS INFORMATION PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the IC. These items are also illustrated graphically in the layout diagram of Figure 9. The ...

Page 24

LTC3835 APPLICATIONS INFORMATION MOSFET components to the sensitive current and voltage sensing traces. In addition, investigate common ground path voltage pickup between these components and the SGND pin of the IC. An embarrassing problem, which can be missed in an ...

Page 25

TYPICAL APPLICATIONS INTV CC 100k 100k 0.01µF 560pF 100pF 35k 39.2k 432k 0.01µF 3300pF 100pF 2.49k 169k 215k 100pF M1, M2: Si4840DY L1: TOKO DS3LC A915AY-3R3M High Efficiency 9.5V, 3A Step-Down Converter CLKOUT V IN PLLLPF TG RUN C B ...

Page 26

LTC3835 TYPICAL APPLICATIONS 0.01µF 470pF 100pF 10k 69.8k 365k INTV CC GND 10k 0.01µF 2.2nF 100pF 10k 118k 59k 26 High Efficiency 5V, 5A Step-Down Converter CLKOUT V IN PLLLPF TG RUN C B 0.22µF PGOOD TRACK/SS BOOST I TH ...

Page 27

PACKAGE DESCRIPTION (Reference LTC DWG # 05-08-1663 Rev H) 6.60 ±0.10 4.50 ±0.10 SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 0.50 – 0.75 (.0035 – .0079) (.020 – .030) NOTE: 1. ...

Page 28

LTC3835 PACKAGE DESCRIPTION 2.65 ± 0.05 4.50 ± 0.05 1.50 REF 3.10 ± 0.05 3.65 ± 0.05 0.25 ±0.05 0.50 BSC 2.50 REF 4.10 ± 0.05 5.50 ± 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS ...

Page 29

... Updated Table 1 Updated Related Parts Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. LTC3835 ...

Page 30

... QFN-12 ≤ 5.25V, MSOP-16E, 3mm × 3mm QFN-16, SSOP- ≤ V ≤ 36V 80µ with One Channel On LT 1110 REV D • PRINTED IN USA  LINEAR TECHNOLOGY CORPORA TION 2008 ≤ 60V, ≤ 38V, ≤ 38V, ≤ 38V, IN 3835fd ...