LTC3835 Linear Technology, LTC3835 Datasheet
LTC3835
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LTC3835 Summary of contents
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... OPTI-LOOP compensa- tion allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3835 features a precision 0.8V reference and a power good output indicator. The 4V to 36V input supply range Applications encompasses a wide range of battery chemistries. ...
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... 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 www.datasheet4u.com INTV , (BOOST-SW), CLKOUT, PGOOD ... 8.5V to –0.3V CC RUN, TRACK/SS ......................................... 7V to –0.3V + – SENSE , SENSE Voltages ........................ 11V to –0.3V PLLIN/MODE, PHASMD, PLLLPF ......... INTV EXTV ...................................................... 10V to – ...
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... LTC3835EUFD LTC3835EUFD#TR LTC3835IUFD LTC3835IUFD#TR Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi ...
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... FB V Ramping Positive FB Note 4: The LTC3835 is tested in a feedback loop that servos V specifi ed voltage and measures the resultant V Note 5: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. See Applications Information. Note 6: Rise and fall times are measured using 10% and 90% levels. ...
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... Continuous Mode) V OUT 100mV/DIV AC COUPLED I L 2A/DIV 3835 G04 20μs/DIV FIGURE 11 CIRCUIT V = 3.3V OUT Soft Start-Up 3835 G07 20ms/DIV FIGURE 11 CIRCUIT LTC3835 T = 25ºC, unless otherwise noted. A Effi ciency vs Input Voltage 3.3V OUT 82 100 1000 10000 0 ...
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... LTC3835 TYPICAL PERFORMANCE CHARACTERISTICS Total Input Supply Current vs Input Voltage www.datasheet4u.com 350 300 250 300μA LOAD 200 150 NO LOAD 100 INPUT VOLTAGE (V) Maximum Current Sense Voltage vs I Voltage TH 100 PULSE SKIPPING FORCED CONTINUOUS 80 BURST MODE (RISING) ...
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... G22 Oscillator Frequency vs Input Voltage 404 402 400 398 396 394 392 INPUT VOLTAGE (V) 3835 G25 LTC3835 T = 25ºC, unless otherwise noted. A Regulated Feedback Voltage vs Temperature 808 806 804 802 800 798 796 794 792 –45 – ...
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... In this case, an R-C fi lter must be connected to the PLLLPF pin. When not synchronizing to an external clock, this input determines how the LTC3835 operates at light loads. Pulling this pin below 0.7V selects Burst Mode operation. power, bypass- ...
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... BOT FC TOP FB1 BURSTEN B + 0.4V SLEEP – SHDN ICMP + – – – – + 6mV 0.45V 2 SLOPE COMP OV 0.5μA 6V RUN LTC3835 INTV BOOST TOP SW SWITCH INTV CC LOGIC BG BOT PGND SENSE – SENSE – TRACK/ ...
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... TRACK/SS pin an external resistor divider from the other supply to ground (see CC Applications Information section). When the RUN pin is pulled low to disable the LTC3835, or when V of 3.5V, the TRACK/SS pin is pulled low by an internal MOSFET. When in undervoltage lockout, the controller is disabled and the external MOSFETs are held off ...
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... PLLIN/MODE pin. In this case, a series R-C should be connected between the PLLLPF pin and SGND to serve as the PLL’s loop fi lter. The LTC3835 phase detector adjusts the voltage on the PLLLPF pin to align the turn-on of the external top MOSFET to the rising edge of the synchronizing signal ...
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... 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 www.datasheet4u.com words, the LTC3835’s PLL is guaranteed to lock to an external clock source whose frequency is between 140kHz and 650kHz. The typical input clock thresholds on the PLLIN/MODE pin are 1 ...
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... However, lower frequency operation requires more inductance for a given amount of ripple current. The internal oscillator of the LTC3835 runs at a nominal 400kHz frequency when the PLLLPF pin is left fl oating and the PLLIN/MODE pin low or high. Pulling the PLLLPF to INTV selects 530kHz operation ...
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... Power MOSFET and Schottky Diode (Optional) Selection Two external power MOSFETs must be selected for the LTC3835: One N-channel MOSFET for the top (main) switch, and one N-channel MOSFET for the bottom (syn- chronous) switch. The peak-to-peak drive levels are set by the INTV This voltage is typically 5V during start-up (see EXTV Connection) ...
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... The output ripple is highest at maximum input voltage since I increases with input voltage. RIPPLE Setting Output Voltage The LTC3835 output voltage is set by an external feed- back resistor divider carefully placed across the output, as shown in Figure 1. The regulated output voltage is determined by: ⎛ ...
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... The start- controlled by the voltage on the OUT www.datasheet4u.com TRACK/SS pin. When the voltage on the TRACK/SS pin is less than the internal 0.8V reference, the LTC3835 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 CC LDO regulates Using the EXTV IN control power to be derived from the LTC3835 switching CC regulator output (4.7V ≤ V operation and from the V of regulation (e.g., startup, short-circuit). If more cur-rent is required through the EXTV external Schottky diode can be added between the EXTV ...
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... Under short-circuit conditions with very low duty cycles, the LTC3835 will begin cycle skipping in order to limit the short-circuit current. In this situation the 1μF bottom MOSFET will be dissipating most of the power but less than in normal operation. The short-circuit ripple cur- 0.22μ ...
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... PLLIN/MODE, is shown in Figure 7 and specifi the Electrical Characteristics table. Note that the LTC3835 can only be synchronized to an external clock whose frequency is within range of the LTC3835’s internal VCO, which is nominally 115kHz to 800kHz. This is guaranteed to be between 140kHz and 650kHz. A simplifi ed block diagram is shown in Figure 8 ...
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... Minimum on-time t is the smallest time duration ON(MIN) www.datasheet4u.com that the LTC3835 is capable of turning on the top 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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... LOAD loop response. The gain of the loop will be increased by increasing R increased by decreasing C factor that C the same, thereby keeping the phase shift the same in the LTC3835 external components shown in the Typical TH series RC-CC fi lter sets the dominant pole-zero pin waveforms that will TH ...
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... 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 www.datasheet4u.com overall supply performance. A second, more severe transient is caused by switching in loads with large (>1μF) supply bypass capacitors. The ...
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... All of these nodes have very large and fast moving signals and therefore should be kept on the “output side” of the LTC3835 and occupy minimum PC trace area. 7. Use a modifi ed “star ground” technique: a low imped- ance, large copper area central grounding point on ...
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... SGND pin of the IC. An embarrassing problem, which can be missed in an otherwise properly working switching regulator, results when the current sensing leads are hooked up backwards. C1 1nF Figure 9. LTC3835 Recommended Printed Circuit Layout Diagram BOLD LINES INDICATE HIGH SWITCHING CURRENT ...
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... TRACK/SS BOOST LTC3835 D B 100pF CMDSH-3 SGND INTV CC 4.7μF PLLIN/MODE EXTV – SENSE + SENSE PGND 100pF LTC3835 36V 10μF 7.2μH 0.012Ω V OUT 9. OUT 150μF M2 3835 TA02 V IN 12V 10μF L1 3.3μ ...
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... – SENSE + SENSE PGND High Effi ciency 1.2V, 5A Step-Down Converter CLKOUT V IN GND PLLLPF TG RUN C B 0.22μF PGOOD TRACK/SS BOOST LTC3835 D B 100pF CMDSH-3 SGND INTV CC 4.7μF PLLIN/MODE EXTV – SENSE + SENSE PGND 36V 10μ ...
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... SHALL NOT EXCEED 0.150mm (.006") PER SIDE UFD Package 20-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1711 Rev B) 4.00 0.10 (2 SIDES) 0.70 0.05 PIN 1 TOP MARK (NOTE 6) 5.00 0.10 (2 SIDES) PACKAGE OUTLINE LTC3835 6.40 – 6.60* (.252 – .260) 3.86 (.152 6.40 2.74 (.252) (.108) BSC ...
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... Linear Technology Corporation 28 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● CLKOUT V IN PLLLPF TG RUN C B 0.22μF PGOOD TRACK/SS BOOST LTC3835 D B 100pF CMDSH-3 SGND INTV CC 4.7μF PLLIN/MODE EXTV – SENSE + SENSE PGND 39pF Figure 11. High Effi ciency Step-Down Converter ...