LTC3858-1 Linear Technology Corporation, LTC3858-1 Datasheet
LTC3858-1
Related parts for LTC3858-1
LTC3858-1 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 LTC3858-1 features a precision 0.8V reference and a power good output indicator. A wide 4V to 38V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries ...
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... LTC3858-1 www.DataSheet4U.com ABSOLUTE MAXIMUM RATINGS Input Supply Voltage (V ) ......................... –0.3V to 40V IN Topside Driver Voltages BOOST1, BOOST2 ................................. –0.3V to 46V Switch Voltage (SW1, SW2) ........................ –5V to 40V (BOOST1-SW1), (BOOST2-SW2) ................ –0. RUN1, RUN2 ............................................... –0. Maximum Current Sourced Into Pin from Source >8V...............................................100μ – ...
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... RUN1 RUN2 Rising from 1V SS1 SS2 Rising from 2V SS1 SS2 Soft-Start Condition V OSENSE1 4.5V SS1 0.7V, V –, – = 3.3V FB1,2 SENSE1 2 LTC3858-1 = 5V, EXTV = 0V unless otherwise noted. CC MIN TYP 4 l 0.792 0.800 l 0.788 0.800 0.792 0.800 ±5 0.002 l 0.01 l –0.01 2 1.3 2 170 ...
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... V Ramping Positive FB Hysteresis Note 4: The LTC3858-1 is tested in a feedback loop that servos V a specifi ed voltage and measures the resultant V the specifi cation at 85°C is not tested in production. This specifi cation is assured by design, characterization and correlation to production testing at 125°C. ...
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... G03 Inductor Current at Light Load FORCED CONTINUOUS MODE Burst Mode OPERATION 2A/DIV PULSE SKIPPING MODE 3858 G06 V = 3.3V 2μs/DIV OUT I = 200μA LOAD FIGURE 12 CIRCUIT LTC3858-1 Effi ciency vs Load Current 100 12V 3.3V ...
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... LTC3858-1 www.DataSheet4U.com TYPICAL PERFORMANCE CHARACTERISTICS Total Input Supply Current vs Input Voltage 400 FIGURE 12 CIRCUIT V = 3.3V 350 OUT ONE CHANNEL ON 300 300μA LOAD 250 200 NO LOAD 150 100 INPUT VOLTAGE (V) Maximum Current Sense Voltage vs I Voltage TH 80 PULSE-SKIPPING MODE ...
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... INPUT VOLTAGE (V) 3858 G22 3858 G28 LTC3858-1 Regulated Feedback Voltage vs Temperature 808 806 804 802 800 798 796 794 792 130 105 –45 – TEMPERATURE (°C) 3858 G20 Oscillator Frequency vs Temperature ...
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... RUN1, RUN2 (Pins 6, 8/Pins 7, 9): Digital Run Control Inputs for Each Controller. Forcing either of these pins below 1.2V shuts down that controller. Forcing both of these pins below 0.7V shuts down the entire LTC3858-1, reducing quiescent current to approximately 8μA. Do NOT fl oat these pins. ...
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... This LDO supplies CC SS1, SS2 (Pins 26, 28/Pins 12, 14): External Soft-Start Input. The LTC3858-1 regulates the V CC the smaller of 0.8V or the voltage on the SS1,2 pin. An internal 1μA pull-up current source is connected to this pin. A capacitor to ground at this pin sets the ramp time to fi ...
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... SGND OPERATION Main Control Loop The LTC3858-1 uses a constant frequency, current mode step-down architecture with the two controller channels operating 180 degrees out of phase. During normal op- eration, each external top MOSFET is turned on when the clock for that channel sets the RS latch, and is turned off when the main current comparator, ICMP , resets the RS latch ...
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... V on the SS pin at the time the short-circuit occurs. Normally the SS pin voltage will have been pulled up to the INTV voltage (5.1V) by the internal 1μA pull-up current. Note that the two controllers on the LTC3858-1 have sepa long as rate, independent short-circuit latchoff circuits. Latchoff IN ...
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... LATCH draws only 170μA of quiescent current. If both channels are in sleep mode, the LTC3858-1 draws only 300μA of qui- escent current. In sleep mode, the load current is supplied by the output capacitor. As the output voltage decreases, the EA’s output begins to rise. When the output voltage ...
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... Placing a resistor between FREQ and SGND allows the frequency to be programmed between 50kHz and 900kHz. A phase-locked loop (PLL) is available on the LTC3858-1 to synchronize the internal oscillator to an external clock source that is connected to the PLLIN/MODE pin. The phase detector adjusts the voltage (through an internal lowpass fi ...
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... EMI and improves real world operating effi ciency. Figure 2 compares the input waveforms for a representative single phase dual switching regulator to the LTC3858-1 2-phase dual switching regulator. An actual measure- ment of the RMS input current under these conditions shows that 2-phase operation dropped the input current from 2 ...
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... The SENSE and SENSE pins are the inputs to the current comparators. The common mode voltage range on these pins 28V (Abs Max), enabling the LTC3858-1 to regulate output voltages nominal 24V (allowing margin for tolerances and transients). + The SENSE pin is high impedance over the full common mode range, drawing at most ± ...
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... LTC3858-1 www.DataSheet4U.com APPLICATIONS INFORMATION Low Value Resistors Current Sensing A typical sensing circuit using a discrete resistor is shown in Figure 5a chosen based on the required SENSE output current. The current comparator has a maximum threshold V of 50mV (typ). The current comparator thresh- SENSE(MAX) old voltage sets the peak of the inductor current, yielding a maximum average output current, I peak value less half the peak-to-peak ripple current, Δ ...
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... Power MOSFET and Schottky Diode (Optional) Selection decreases with higher L Two external power MOSFETs must be selected for each controller in the LTC3858-1: one N-channel MOSFET for the top (main) switch, and one N-channel MOSFET for the ⎞ bottom (synchronous) switch. ⎠ ⎟ ...
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... LTC3858-1 www.DataSheet4U.com APPLICATIONS INFORMATION Selection criteria for the power MOSFETs include the on- resistance Miller capacitance, C DS(ON) voltage and maximum output current. Miller capacitance can be approximated from the gate charge curve MILLER usually provided on the MOSFET manufacturers’ data sheet equal to the increase in gate charge ...
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... The output ripple is highest at maximum input voltage since ΔI Setting Output Voltage The LTC3858-1 output voltages are each set by an exter- nal feedback resistor divider carefully placed across the output, as shown in Figure 6. The regulated output voltage is determined by: ...
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... LTC3858-1 www.DataSheet4U.com APPLICATIONS INFORMATION linear ramping voltage at the SS pin. The LTC3858-1 will regulate the V pin (and hence V FB voltage on the SS pin, allowing its fi nal regulated value. The total soft-start time will be approximately • μA INTV Regulators ...
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... In this situation the bottom MOSFET will be dissipating most of the power but less than in normal operation. The short-circuit ripple current is determined by the minimum on-time, t BAT85 of the LTC3858-1 (≈90ns), the input voltage and inductor value: BAT85 VN2222LL ΔI ...
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... VCO input voltage is not required, it will avoid sweeping the oscillator from 350kHz or 535kHz to the fi nal PLL frequency. Note that the LTC3858-1 can only be synchronized to an external clock whose frequency is within range of the LTC3858-1’s internal VCO, which is nominally 50kHz to 900kHz ...
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... Minimum On-Time Considerations Minimum on-time the smallest time dura- ON(MIN) tion that the LTC3858-1 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 ...
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... A 25W supply will typically require a minimum of 20μF to 40μF of capacitance having a maximum of 20mΩ to 50mΩ of ESR. The LTC3858-1 2-phase architecture typically halves this input capacitance requirement over competing solu- tions. 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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... C chosen with an ESR of 0.02Ω for low output ripple volt- age. 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 = 77.7k yields B LTC3858-1 = 0.035Ω/0.022Ω, C DS(ON) MILLER ( ) ( ) ( 3 3 ...
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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 LTC3858-1 and occupy minimum PC trace area. 7. Use a modifi ed “star ground” technique: a low imped- ...
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... V IN PLLIN/MODE RUN1 PGND RUN2 EXTV V CC OUT1 SGND – INTV SENSE2 CC + SENSE2 BG2 BOOST2 V FB2 SW2 I TH2 TG2 SS2 Figure 10. Recommended Printed Circuit Layout Diagram LTC3858-1 V PULL-UP (<6V SENSE OUT1 1μ VIN CERAMIC INTVCC OUT2 1μ ...
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... LTC3858-1 www.DataSheet4U.com APPLICATIONS INFORMATION BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. 28 SW1 L1 R SENSE1 D1 C OUT1 SW2 L2 R SENSE2 D2 C OUT2 Figure 11. Branch Current Waveforms V OUT1 OUT2 R L2 38581 F11 38581f ...
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... Compensation of the voltage loop will be much more sensitive to component selection. This behavior can be investigated by temporarily shorting out the current sensing resistor—don’t worry, the regulator will still maintain control of the output voltage. LTC3858-1 , Schottky and the top IN 38581f 29 ...
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... Effi ciency vs Output Current 100 8. 3.3V OUT OUT 12V IN Burst Mode OPERATION 0 0.00001 0.0001 0.001 0.01 0.1 1 OUTPUT CURRENT (A) 30 LTC3858-1 + SENSE1 INTV CC 100k – SENSE1 PGOOD1 V BG1 FB1 SW1 C B1 BOOST1 0.47μF TG1 I TH1 SS1 INTV CC C INT 4.7μF ...
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... PGND PLLIN/MODE D2 SGND EXTV TG2 CC RUN1 C B2 RUN2 BOOST2 0.47μF FREQ SW2 SS2 I BG2 TH2 V FB2 – SENSE2 + SENSE2 : SANYO 10TPD150M LTC3858-1 L1 MBOT1 2.4μH V OUT1 2. SENSE1 OUT1 7mΩ 150μF MTOP1 38V C IN 22μF MTOP2 L2 R SENSE2 3.2μH 7mΩ ...
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... SENSE1 INTV CC C1 100k 1nF – SENSE1 PGOOD1 V BG1 FB1 SW1 C B1 BOOST1 0.47μF 46k ITH1 TG1 I TH1 D1 C 0.01μF SS1 LTC3858-1 V SS1 IN INTV CC C INT 4.7μF PGND PLLIN/MODE D2 SGND EXTV TG2 CC RUN1 C B2 BOOST2 RUN2 0.47μF FREQ C 0.01μF SS2 SW2 ...
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... ITH2A V FB2 – SENSE2 SANYO 2R5TPE220M OUT1 OUT2 C2 L1, L2: SUMIDA IHL P2525CZERR47M06 0.1μF MTOP1, MTOP2: RENESAS RJK0305 + SENSE2 MBOT1, MBOT2: RENESAS RJK0328 R 1.18k S2 LTC3858-1 L1 MBOT1 0.47μH V OUT1 OUT1 SENSE1 220μF 4mΩ 2 MTOP1 V IN 12V C IN 22μF ...
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... LTC3858-1 www.DataSheet4U.com PACKAGE DESCRIPTION 4.50 0.05 3.10 0.05 2.50 REF 2.65 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 5.00 0.10 (2 SIDES) NOTE: 1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WXXX-X). 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH ...
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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 LTC3858-1 .386 – .393* (9.804 – 9.982) (0.838 1615 .150 – .157** (3.810 – ...
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