ltc3890-1 Linear Technology Corporation, ltc3890-1 Datasheet
ltc3890-1
Related parts for ltc3890-1
ltc3890-1 Summary of contents
Page 1
... SENSE2 0.01Ω – V SENSE2 OUT2 8.5V V FB2 3A 100k ITH2 1000pF 330μF TRACK/SS2 10.5k 34.8k 0.1μF 38901 TA01 LTC3890-1 60V Low I 3890 high performance dual step-down ® compensation Effi ciency and Power Loss vs Output Current (Buck) 100 V = 12V 3.3V 90 OUT ...
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... LTC3890-1 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (V ) ......................... –0.3V to 65V IN Topside Driver Voltages BOOST1, BOOST2 ................................. –0.3V to 71V Switch Voltage (SW1, SW2) ........................ –5V to 65V (BOOST1-SW1), (BOOST2-SW2) ................ –0. RUN1, RUN2 ............................................... –0. Maximum Current Sourced into Pin from Source >8V .......................................................100μ – ...
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... LOAD C = 3300pF Each Driver LOAD C = 3300pF Each Driver LOAD (Note 7) 6V < V < 60V EXTVCC I = 0mA to 50mA EXTVCC 6V < V < 13V EXTVCC LTC3890 unless otherwise noted. CC MIN TYP MAX UNITS 2 mmho μA 60 100 μ μ ...
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... V Ramping Positive FB Hysteresis Note 4: The LTC3890-1 is tested in a feedback loop that servos V a specifi ed voltage and measures the resultant V 85°C is not tested in production. This specifi cation is assured by design, characterization and correlation to production testing at 125°C. Note 5: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency ...
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... Pulse-Skipping Mode V OUT 100mV/DIV AC- COUPLED I L 2A/DIV 50μs/DIV V = 12V 3.3V OUT FIGURE 13 CIRCUIT Soft Start-Up V OUT2 2V/DIV V OUT1 2V/DIV 38901 G07 2ms/DIV FIGURE 13 CIRCUIT LTC3890-1 Effi ciency vs Input Voltage 100 OUT2 3.3V 88 OUT1 LOAD ...
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... LTC3890-1 TYPICAL PERFORMANCE CHARACTERISTICS Total Input Supply Current vs Input Voltage 300 250 200 300μA 150 100 NO LOAD INPUT VOLTAGE (V) 38901 G10 Maximum Current Sense Voltage vs I Voltage PULSE SKIPPING MODE 40 Burst Mode ...
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... Oscillator Frequency vs Input Voltage 356 FREQ = GND 354 352 350 348 346 344 130 INPUT VOLTAGE (V) LTC3890-1 Regulated Feedback Voltage vs Temperature 800 806 804 802 800 798 796 794 792 –45 – 105 130 TEMPERATURE (° ...
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... RUN1, RUN2 (Pin 8, Pin 9): Digital Run Control Inputs for set Each Controller. Forcing either of these pins below 1.2V SENSE shuts down that controller. Forcing both of these pins below 0.7V shuts down the entire LTC3890-1, reducing quiescent current to approximately 14μA. INTV (Pin 19): Output of the Internal Linear Low Dropout CC Regulator ...
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... A capacitor to ground this pin sets the ramp time to fi nal regulated output volt- age. Alternatively, a resistor divider on another voltage supply connected to this pin allows the LTC3890-1 output to track the other supply during start-up. – 0.5V CC LTC3890-1 FB1 voltage to the smaller of 0 ...
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... LTC3890-1 FUNCTIONAL DIAGRAM PGOOD1 + 0.88V – V FB1 + – 0.72V 20μA FREQ VCO C LP SYNC DET PLLIN/MODE 100k V IN EXTV CC 5.1V 5.1V LDO LDO – 4.7V SGND INTV CC 10 DUPLICATE FOR SECOND CONTROLLER CHANNEL DROP OUT DET CLK2 + 0.425V CLK1 – ICMP PFD – ...
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... Using the EXTV CC CC the INTV power to be derived from a high effi ciency CC external source such as one of the LTC3890-1 switching regulator outputs. Each top MOSFET driver is biased from the fl oating boot- strap capacitor C , which normally recharges during each B cycle through an external diode when the top MOSFET turns off ...
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... Light Load Current Operation (Burst Mode Operation, Pulse Skipping, or Forced Continuous Mode) (PLLIN/MODE Pin) The LTC3890-1 can be enabled to enter high effi ciency Burst Mode operation, constant frequency pulse skipping mode, or forced continuous conduction mode at low load currents. To select Burst Mode operation, tie the PLLIN/ MODE pin voltage below 0 ...
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... The typical capture range of the phase-locked loop is from approximately 55kHz to 1MHz, with a guarantee to be between 75kHz and 850kHz. In other words, the LTC3890-1’s PLL is guaranteed to lock to an external clock source whose frequency is between 75kHz and 850kHz. The typical input clock thresholds on the PLLIN/MODE pin are 1 ...
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... The schematic on the fi rst page is a basic LTC3890-1 ap- plication circuit. External component selection is driven by the load requirement, and begins with the selection of R and the inductor value ...
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... CC the smaller current to the higher current. Filter components mutual to the sense lines should be placed close to the LTC3890-1, and the sense lines should run close together to a Kelvin connection underneath the current sense element (shown in Figure 3). Sensing cur- rent elsewhere can effectively add parasitic inductance ...
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... Inductor DCR Sensing For applications requiring the highest possible effi ciency at high load currents, the LTC3890-1 is capable of sensing the voltage drop across the inductor DCR, as shown in Figure 4b. The DCR of the inductor represents the small amount of DC resistance of the copper wire, which can be less than 1mΩ ...
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... Do not allow the core to saturate! Power MOSFET and Schottky Diode (Optional) Selection Two external power MOSFETs must be selected for each controller in the LTC3890-1: one N-channel MOSFET for the top (main) switch, and one N-channel MOSFET for the : IN bottom (synchronous) switch. ...
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... LTC3890-1 APPLICATIONS INFORMATION The peak-to-peak drive levels are set by the INTV voltage. This voltage is typically 5.1V during start-up (see EXTV Pin Connection). Consequently, logic-level CC threshold MOSFETs must be used in most applications. Pay close attention to the BV DSS MOSFETs as well. Selection criteria for the power MOSFETs include the ...
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... Always consult the manufacturer IN if there is any question. The benefi the LTC3890-1 2-phase operation can be calculated by using Equation 1 for the higher power control- ler and then calculating the loss that would have resulted if both controller channels switched on at the same time. ...
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... TRACK/ X according to the ratio Figure 8. Using the TRACK/SS Pin for Tracking INTV Regulators CC TRACKB The LTC3890-1 features two separate internal P-channel B low dropout linear regulators (LDO) that supply power during start-up): at the INTV EXTV pin depending on the connection of the EXTV CC pin. INTV LTC3890-1’ ...
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... CC Using the EXTV LDO allows the MOSFET driver and CC control power to be derived from one of the LTC3890-1’s switching regulator outputs (4.7V ≤ V normal operation and from the V put is out of regulation (e.g., start-up, short-circuit). If more current is required through the EXTV is specifi ed, an external Schottky diode can be added ...
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... Under BAT85 short-circuit conditions with very low duty cycles, the LTC3890-1 will begin cycle skipping in order to limit the BAT85 NDS7002 short-circuit current. In this situation the bottom MOSFET ...
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... Minimum On-Time Considerations Minimum on-time the smallest time dura- ON(MIN) tion that the LTC3890-1 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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... LTC3890-1 APPLICATIONS INFORMATION The minimum on-time for the LTC3890-1 is approximately 90ns. However, as the peak sense voltage decreases the minimum on-time gradually increases up to about TBDns. This is of particular concern in forced continuous applica- tions with low ripple current at light loads. If the duty cycle drops below the minimum on-time limit in this situation, a signifi ...
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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 LTC3890-1 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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... LTC3890-1 APPLICATIONS INFORMATION Design Example As a design example for one channel, assume V 12V(nominal 22V (max OUT V = 75mV and f = 350kHz. SENSE(MAX) The inductance value is chosen fi rst based on a 30% ripple current assumption. The highest value of ripple current occurs at the maximum input voltage. Tie the FREQ pin to GND, generating 350kHz operation ...
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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 LTC3890-1 and occupy minimum PC trace area. 7. Use a modifi ed star ground technique: a low impedance, ...
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... LTC3890-1 APPLICATIONS INFORMATION and possibly BG connections and the sensitive voltage and current pins. The capacitor placed across the current sensing pins needs to be placed immediately adjacent to the pins of the IC. This capacitor helps to minimize the effects of differential noise injection due to high frequency capacitive coupling ...
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... TRACK/SS1 PGOOD1 FB1 + TG1 – SW1 LTC3890 BOOST1 BG1 V IN PGND EXTV CC C INTVCC – INTV CC + BG2 BOOST2 FB2 C B2 SW2 TG2 LTC3890-1 R PU1 V PULL-UP PGOOD1 L1 R SENSE OUT1 1μ CERAMIC VIN + + OUT2 1μF CERAMIC ...
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... LTC3890-1 APPLICATIONS INFORMATION BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. 30 SW1 L1 R SENSE1 D1 C OUT1 SW2 L2 R SENSE2 D2 C OUT2 Figure 12. Branch Current Waveforms V OUT1 OUT2 R L2 38901 F12 38901f ...
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... Effi ciency vs Load Current 100 V = 8.5V OUT 3.3V OUT 12V IN 0 0.0001 0.001 0.01 0.1 1 OUTPUT CURRENT (A) 38901 TA07c LTC3890-1 MBOT1 R SENSE1 8mΩ V OUT1 3. 4.7μH C OUT1 470μF MTOP1 60V C IN 220μF MTOP2 L2 R SENSE2 8μH 10mΩ V OUT2 8 ...
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... L1, L2: COILCRAFT SER1360-802KL C OUT1 D1, D2: DFLS1100 32 High Effi ciency 8.5V Dual-Phase Step-Down Converter + SENSE1 INTV C1 CC 1nF 100k – SENSE1 PGOOD1 V FB1 BG1 SW1 BOOST1 ITH1 C LTC3890-1 B1 0.1μF TRACK/SS1 TG1 PLLIN/MODE INTV CC C SGND 4.7μF PGND EXTV CC RUN1 D2 RUN2 FREQ TG2 C 0.1μ ...
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... RUN1 D2 RUN2 FREQ TG2 C 0.47μF B2 BOOST2 TRACK/SS2 SW2 ITH2 BG2 V FB2 – SENSE2 C2 1nF + SENSE2 : 16SVP180MX OUT1 : SANYO 6TPE470M OUT2 LTC3890-1 MBOT1 R SENSE1 9mΩ V OUT1 12V OUT1 8μH 180μF MTOP1 V IN 12.5V TO 60V C IN 220μF INT MTOP2 L2 R SENSE2 4.7μ ...
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... OUT1 C OUT2 D1, D2: DFLS1100 34 High Effi ciency Dual 24V/5V Step-Down Converter + SENSE1 INTV CC C1 1nF 100k – SENSE1 PGOOD1 V FB1 BG1 SW1 BOOST1 ITH1 C LTC3890-1 B1 0.47μF TRACK/SS1 TG1 PLLIN/MODE INTV CC C INT SGND 4.7μF PGND EXTV CC RUN1 D2 RUN2 FREQ TG2 C 0.47μ ...
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... BSC .015 .004 45 .0532 – .0688 (0.38 0.10) (1.35 – 1.75) 0 – 8 TYP .008 – .012 (0.203 – 0.305) TYP LTC3890-1 .386 – .393* .033 (9.804 – 9.982) (0.838 1615 REF .150 – ...
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... LTC3890-1 TYPICAL APPLICATION + SENSE1 1nF 100k – SENSE1 R A1 6.98k V FB1 C 100pF ITH1A R C 470pF ITH1 ITH1 34.8k ITH1 C 0.01μF LTC3890-1 SS1 TRACK/SS1 PLLIN/MODE SGND EXTV CC RUN1 R FREQ RUN2 41.2k FREQ C 0.01μF SS2 TRACK/SS2 R C 1000pF ITH2 ITH2 34.8k ITH2 C ITH2A 100pF V FB2 ...