LTC3850-2 Linear Technology, LTC3850-2 Datasheet
LTC3850-2
Related parts for LTC3850-2
LTC3850-2 Summary of contents
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... OPTI-LOOP to be optimized over a wide range of output capacitance and ESR values. The LTC3850-2 features a precision 0.8V reference and a power good output indicator. A wide 4V to 30V input supply range encompasses most battery chemistries and intermediate bus voltages. ...
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... LTC3850-2 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (V ) ......................... 30V to –0.3V IN Input Supply Transient Voltage (V www.datasheet4u.com INTV ≥ 5V ........................................... 34V to –0.3V CC Top Side Driver Voltages BOOST1, BOOST2 .................................. 34V to –0.3V Switch Voltage (SW1, SW2) ......................... 30V to –5V INTV , RUN1, RUN2, PGOOD, EXTV CC (BOOST1-SW1), (BOOST2-SW2) ................. 6V to –0.3V ...
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... LOAD C = 3300pF Each Driver LOAD C = 3300pF Each Driver LOAD (Note 7) 7V < V < 24V 0mA to 50mA CC EXTV Ramping Positive 20mA EXTVCC LTC3850-2 = 5V, unless otherwise noted. MIN TYP MAX l 0.792 0.800 0.808 –10 –50 0.002 0.02 l 0.01 l –0.01 –0.1 2 850 OUT1 ...
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... LTC3850-2 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T SYMBOL PARAMETER Oscillator and Phase-Locked Loop www.datasheet4u.com f Nominal Frequency NOM f Lowest Frequency LOW f Highest Frequency HIGH R MODE/PLLIN Input Resistance MODE/PLLIN I Phase Detector Output Current FREQ Sinking Capability Sourcing Capability PGOOD Output ...
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... OPERATION 2A/DIV PULSE-SKIPPING MODE 2A/DIV 38502 G06 40μs/DIV = 1.8V 2V/DIV V TK/SS 500mV/DIV V OUT2 1.5Ω LOAD 1V/DIV 38502 G08 2.5ms/DIV LTC3850-2 Load Step (Forced Continuous Mode) I LOAD OUT 38502 G05 40μs/DIV CIRCUIT OF FIGURE 12V 1.8V IN OUT Inductor Current at Light Load 38502 G07 1μ ...
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... LTC3850-2 TYPICAL PERFORMANCE CHARACTERISTICS Tracking Up and Down with External Ramp www.datasheet4u.com TK/SS1 TK/SS2 2V/DIV V OUT1 3.3V 3Ω LOAD 1V/DIV V OUT2 1.8V 1.5Ω LOAD 1V/DIV 10ms/DIV Current Sense Threshold vs I Voltage –20 –40 0 0.5 1 1.5 V (V) ITH Maximum Current Sense Voltage vs Feedback Voltage (Current Foldback) ...
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... Oscillator Frequency vs Input Voltage 420 410 400 390 380 100 INPUT VOLTAGE (V) 38502 G21 100 25 75 38502 G24 LTC3850-2 Oscillator Frequency vs Temperature 900 V = INTV FREQ 800 700 600 V = 1.2V FREQ 500 400 300 FREQ 200 75 100 –50 –25 ...
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... LTC3850-2 PIN FUNCTIONS RUN1, RUN2 (Pin 1, Pin 13): Run Control Inputs. A voltage above 1.2V on either pin turns on the IC. However, forcing either of these pins below 1.2V causes the IC to shut down www.datasheet4u.com that particular channel. There are 0.5μA pull-up currents for these pins. Once the RUN pin rises above 1.2V, an additional 4.5μ ...
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... Q ON SWITCH LOGIC – AND ANTI- I REV SHOOT + THROUGH RUN OV UVLO SLOPE RECOVERY ACTIVE CLAMP SS RUN – + – + 0.64V 1. RUN TK/ LTC3850 INTV CC BOOST SENSE D B – SENSE VCC PGND PGOOD + 0.74V – ...
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... IN Light Load Current Operation (Burst Mode Operation, Pulse-Skipping, or Continuous Conduction) The LTC3850-2 can be enabled to enter high effi ciency Burst Mode operation, constant-frequency pulse-skipping mode, or forced continuous conduction mode. To select forced continuous operation, tie the MODE/PLLIN pin voltage below 0.8V (e.g., SGND). To select pulse-skipping rises smoothly from zero to its fi ...
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... The PGOOD pin is pin, just as in nor- TH also pulled low when either RUN pin is below 1.2V or when the LTC3850 the soft-start or tracking phase. When pin voltage is within the ±7.5% requirement, the the V FB MOSFET is turned off and the pin is allowed to be pulled external resistor to a source ...
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... Using a Resistor to Sense Current 12 Filter components mutual to the sense lines should be placed close to the LTC3850-2, and the sense lines should run close together to a Kelvin connection underneath the current sense element (shown in Figure 1). Sensing current elsewhere can effectively add parasitic inductance and capacitance to the ...
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... Kelvin connected to the sense resistor. Inductor DCR Sensing For applications requiring the highest possible effi ciency at high load currents, the LTC3850-2 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 winding resistance of the copper, which can be less than 1mΩ ...
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... LTC3850-2 APPLICATIONS INFORMATION www.datasheet4u.com V SENSE 20mV/DIV 500ns/DIV Figure 3. Voltage Waveform Measured Directly Across the Sense Resistor. V SENSE 20mV/DIV 500ns/DIV Figure 4. Voltage Waveform Measured After the Sense Resistor Filter 1000pF , the external R1|| R2 • C1 time constant is chosen to be exactly equal to the L/DCR time constant, the voltage drop across the external capacitor is equal to the drop across the inductor DCR multiplied by R2/(R1 + R2) ...
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... Normally, this results in a reduction of maximum inductor peak cur- rent for duty cycles > 40%. However, the LTC3850-2 uses a patented scheme that counteracts this compensating ramp, which allows the maximum inductor peak current to remain unaffected throughout all duty cycles ...
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... Soft-Start and Tracking ) + The LTC3850-2 has the ability to either soft-start by itself with a capacitor or track the output of another channel • external supply. When one particular channel is confi gured MILLER to soft-start by itself, a capacitor should be connected to ⎤ ...
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... After TK/SS drops below 0.1V, its channel will operate in discontinuous mode. Output Voltage Tracking The LTC3850-2 allows the user to program how its out- put ramps up and down by means of the TK/SS pins. Through these pins, the output can be set up to ei- ther coincidentally or ratiometrically track another supply’ ...
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... LTC3850-2 APPLICATIONS INFORMATION www.datasheet4u.com TIME (5a) Coincident Tracking V OUT1 R3 TO TK/SS2 PIN R4 (6a) Coincident Tracking Setup 18 V OUT1 V OUT2 38502 F03a Figure 5. Two Different Modes of Output Voltage Tracking V V OUT1 OUT2 TK/SS2 V V FB1 FB2 PIN PIN R2 R4 Figure 6. Setup for Coincident and Ratiometric Tracking ...
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... APPLICATIONS INFORMATION High input voltage applications in which large MOSFETs are being driven at high frequencies may cause the maxi- mum junction temperature rating for the LTC3850-2 to www.datasheet4u.com be exceeded. The INTV current, which is dominated CC by the gate charge current, may be supplied by either the 5V linear regulator or EXTV the EXTV pin is less than 4 ...
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... LTC3850-2, ceramic capacitors can also be used for C is high enough. if there is any question. IN The benefi the LTC3850-2 2-phase operation can be calculated by using the equation above for the higher power controller and then calculating the loss that would undervoltage IN have resulted if both controller channels switched on at the same time ...
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... IN current resonances small (0.1μF to 1μF) bypass capacitor between the chip V pin and ground, placed close to the LTC3850-2, is also IN suggested. A 2.2Ω – 10Ω resistor placed between C (C1) and the V pin provides further isolation between IN the two channels. ...
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... Typically R Typically, the external clock (on MODE/PLLIN pin) input high threshold is 1.6V, while the input low thres-hold is 1V. Minimum On-Time Considerations Minimum on-time t the LTC3850-2 is capable of turning on the top MOSFET determined by internal timing delays and the gate 1.5 2 2.5 charge required to turn on the top MOSFET. Low duty ...
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... L1, L2, etc. are the individual losses as a percent- age of input power. Although all dissipative elements in the circuit produce losses, four main sources usually account for most of the losses in LTC3850-2 circuits regulator current losses, 4) Topside MOSFET transition losses. ...
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... LTC3850-2 APPLICATIONS INFORMATION a minimum of 20μF to 40μF of capacitance having a maximum of 20mΩ to 50mΩ of ESR. The LTC3850-2 2-phase architecture typically halves this input capacitance www.datasheet4u.com requirement over competing solutions. Other losses including Schottky conduction losses during dead time and inductor core losses generally account for less than 2% total additional loss ...
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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 LTC3850-2 and occupy minimum PC trace area. If DCR sensing is used, place the top resistor (Figure 2b, R1) close to the switching node. ...
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... HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. 26 TK/SS1 R PU2 V PULL-UP I PGOOD PGOOD TH1 V FB1 + SENSE1 TG1 – SENSE1 SW1 C B1 PLLLPF BOOST1 LTC3850-2 BG1 f IN MODE/PLLIN RUN1 PGND RUN2 EXTV CC SGND C INTVCC – INTV SENSE2 CC + SENSE2 BG2 V BOOST2 FB2 ...
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... C 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. while IN LTC3850-2 22μF 50V D4 M2 0.1μF L2 2.2μH 4 ...
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... LTC3850-2 APPLICATIONS INFORMATION Design Example As a design example for a two channel medium current regu- www.datasheet4u.com lator, assume V = 12V(nominal 3.3V 1.8V, I OUT1 OUT2 MAX1,2 (see Figure 14). The regulated output voltages are determined by: ⎛ ⎞ 0.8V • ⎝ ⎜ ⎠ ⎟ OUT R A Using 20k 1% resistors from both V the top feedback resistors are (to the nearest 1% standard value) 63 ...
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... C 38502 F15 chosen with an ESR of 0.02Ω for low output ripple. The output ripple in continuous mode will be highest at the maximum input voltage. The output voltage ripple due to ESR is approximately: V ORIPPLE LTC3850-2 = 0.023Ω/0.016Ω, C DS(ON) MILLER 3. ...
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... L2: TDK ULF10045T-3R3N6R9 C : SANYO 4TPE220MF OUT1 C : SANYO 6TPE150MI OUT2 30 2.2Ω 1μF 4.7μ PGOOD INTV IN CC TG1 TG2 0.1μF BOOST1 BOOST2 SW1 SW2 LTC3850-2 BG2 BG1 MODE/PLLIN PGND 10Ω FREQ/PLLFLTR + + SENSE1 SENSE2 1000pF – – SENSE1 SENSE2 10Ω RUN1 RUN2 EXTV ...
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... TYPICAL APPLICATIONS www.datasheet4u.com LTC3850-2 38502f 31 ...
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... LTC3850-2 TYPICAL APPLICATIONS www.datasheet4u.com 32 38502f ...
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... SENSE1 SENSE2 0.047μF – – SENSE1 SENSE2 RUN1 RUN2 V V FB1 FB2 I I TH1 TH2 TK/SS1 SGND TK/SS2 100pF 0.1μF 0.1μF LTC3850-2 4.7μF 6. 0.1μF L2 0.75μH 1.2k 1% 4.99k 0.047μF 1% 100pF 10k 1% 100pF 1nF 10nF 2200pF 10k 14k 20k 1% 1% ...
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... TAIYO YUDEN JMK325BJ107MM OUT1 OUT2 Figure 20. 2.5V/5A, 1.2V/5A Core-I/O Converter with Dual Inputs 34 2.2Ω 1μ PGOOD EXTV INTV TG1 TG2 0.1μF BOOST1 BOOST2 SW1 SW2 LTC3850-2 BG2 BG1 MODE/PLLIN PGND FREQ/PLLFLTR + + SENSE1 SENSE2 0.1μF – – SENSE1 SENSE2 RUN1 RUN2 V V FB1 FB2 I ...
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... BSC 1 .015 .004 45 .0532 – .0688 (0.38 0.10) (1.35 – 1.75) 0 – 8 TYP .008 – .012 (0.203 – 0.305) TYP INCHES LTC3850-2 .386 – .393* (9.804 – 9.982) (0.838 1615 .150 – .157** (3.810 – ...
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... QFN and SSOP Packages Synchronous Controller Expandable from 2-Phase to 12-Phase, 4V ≤ V 0.6V ≤ V Expandable PolyPhase from 3-Phase to 12-Phase 30μ Six Phases, 0.8V ≤ V 30μA I 1.23V ≤ V Single Output Version of LTC3850-2 4V ≤ trademark of Linear Technology Corporation. SENSE www.linear.com ● + 2.21k 10μF L1 ...