lt1913 Linear Technology Corporation, lt1913 Datasheet
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lt1913
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lt1913 Summary of contents
Page 1
... RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good fl ag signals when V 91% of the programmed output voltage. The LT1913 is available in 10-Pin 3mm × 3mm DFN packages with ex- posed pads for low thermal resistance. ...
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... Quiescent Current from V IN Quiescent Current from BD Minimum Bias Voltage (BD Pin (Note 1) SYNC Voltage ............................................................20V Operating Junction Temperature Range (Note 2) LT1913E ............................................. –40°C to 125°C LT1913I .............................................. –40°C to 125°C Storage Temperature Range ................... –65°C to 150° ...
Page 3
... Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT1913E is guaranteed to meet performance specifi cations from 0°C to 125°C. Specifi cations over the –40°C to 125°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT1913I specifi ...
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... LT1913 W U TYPICAL PERFOR A CE CHARACTERISTICS Effi ciency 100 V = 12V 24V OUT L = 4.7μ 600kHz 50 0 0.5 1 1.5 2 2.5 3 OUTPUT CURRENT (A) 1913 G01 Maximum Load Current 5.5 TYPICAL 5.0 4.5 MINIMUM 4.0 3 3.3V OUT T = 25°C 3 4.7μ 600kHz 2 INPUT VOLTAGE (V) 1913 G06 Switch Current Limit 6 ...
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... RUN/SS PIN VOLTAGE (V) Error Amp Output Current –10 –20 –30 –40 –50 2.0 –200 –100 0 100 FB PIN ERROR VOLTAGE (mV) LT1913 T = 25°C unless otherwise noted. A Frequency Foldback 1200 R = 34.0k T 1000 800 600 400 200 0 125 150 0 100 200 ...
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... LT1913 W U TYPICAL PERFOR A CE CHARACTERISTICS Minimum Input Voltage 6.5 6.0 5.5 5 OUT 4 ° 4.7μ 600kHz 4 100 1000 10000 LOAD CURRENT (mA) 1913 G21 Switching Waveforms; Discontinuous Operation V SW 5V/DIV I L 0.2A/DIV V OUT 10mV/DIV V = 12V 1μs/DIV 3.3V OUT I = 110mA LOAD ...
Page 7
... PG remains low until the FB pin is within 9% of the fi nal regulation voltage. PG output is valid when V is above 3.6V and RUN/SS is high (Pin 8): The LT1913 regulates the FB pin to 0.790V. Connect the feedback resistor divider tap to this pin. V (Pin 9): The V pin is the output of the internal error ...
Page 8
... LT1913 BLOCK DIAGRAM INTERNAL 0.79V REF RUN/ SYNC 6 SOFT-START PG 7 ERROR AMP + 0.7V – GND – + ∑ SLOPE COMP SWITCH LATCH R OSCILLATOR 200kHz TO 2.4MHz S V CLAMP C + – BOOST ...
Page 9
... The LT1913 contains a power good comparator which trips when the FB pin is at 91% of its regulated value. The PG output is an open-collector transistor that is off when the pin, IN output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the LT1913 is enabled and V LT1913 is above 3.6V. IN 1913f ...
Page 10
... The reason input voltage range depends on the switching frequency is because the LT1913 switch has fi nite minimum on and off times. The switch can turn on for a minimum of ~150ns and turn off for a minimum of ~150ns. ...
Page 11
... L OUT(MAX) where I is the maximum output load current. To OUT(MAX) guarantee suffi cient output current, peak inductor current must be lower than the LT1913’s switch current limit (I The peak inductor current is ΔI /2 L(PEAK) OUT(MAX) L where I is the peak inductor current, I L(PEAK) the maximum output load current, and Δ ...
Page 12
... The input capacitor is required to reduce the resulting voltage ripple at the LT1913 and to force this very high frequency switching current into a tight local loop, minimizing EMI. A 10μF capacitor is capable of this task, but only placed close to the LT1913 and the catch diode (see the PCB Layout section) ...
Page 13
... The LT1913 uses current mode control to regulate the output. This simplifi es loop compensation. In particular, the LT1913 does not require the ESR of the output capacitor for stability, so you are free to use ceramic capacitors to achieve low output ripple and small circuit size. Frequency ...
Page 14
... Figure 2 shows an equivalent circuit for the LT1913 control loop. The error amplifi transconductance amplifi er with fi nite output impedance. The power section, consisting of the modulator, power switch and inductor, is modeled as a transconductance amplifi ...
Page 15
... For proper startup, the minimum input voltage is also limited by the boost circuit. If the input voltage is ramped slowly, or the LT1913 is turned on with its RUN/SS pin when the V OUT output is already in regulation, then the boost capacitor D2 may not be fully charged ...
Page 16
... LT1913 is absent. This may occur in battery charging ap- plications or in battery backup systems where a battery or some other supply is diode OR-ed with the LT1913’s output. If the V pin is allowed to fl oat and the RUN/SS ...
Page 17
... The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LT1913 circuits. However, these capaci- tors can cause problems if the LT1913 is plugged into a live supply (see Linear Technology Application Note 88 for a complete discussion). The low loss ceramic capacitor, ...
Page 18
... SUPPLY + + Figure 9. A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation when the LT1913 is Connected to a Live Supply 18 High Temperature Considerations The PCB must provide heat sinking to keep the LT1913 cool. The Exposed Pad on the bottom of the package must be soldered to a ground plane. This ground should be tied to large copper layers below with thermal vias ...
Page 19
... APPLICATIONS INFORMATION sistance. Because of the large output current capability of the LT1913 possible to dissipate enough heat to raise the junction temperature beyond the absolute maximum of 125°C. When operating at high ambient temperatures, the maximum load current should be derated as the ambient temperature approaches 125°C. ...
Page 20
... L: NEC MPLC0730L3R3 20 3.3V Step-Down Converter RUN/SS BOOST ON OFF LT1913 RT 19k PG SYNC 63.4k FB GND f = 600kHz 2.5V Step-Down Converter OFF RUN/SS BOOST LT1913 RT 15.4k PG SYNC FB 63.4k GND f = 600kHz V OUT 3.3V 3.5A L 0.47μF 3.3μH D 316k 47μF 100k 1913 TA03 V OUT 2.5V 3. 1μF 3.3μH D1 215k 100k 47μ ...
Page 21
... BOOST 0.47μ LT1913 SYNC FB 12.7k GND 100k f = 2MHz 12V Step-Down Converter OFF RUN/SS BOOST LT1913 RT 17.4k PG SYNC FB 63.4k GND f = 600kHz LT1913 V OUT 5V 2.5A L 2.2μH 536k 22μF 1913 TA05 V OUT 12V 3.5A L 0.47μF 8.2μH D 715k 50k 47μF 1913 TA06 1913f 21 ...
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... LT1913 TYPICAL APPLICATIONS V IN 3.6V TO 25V 4.7μF 680pF D: ON SEMI MBRA340 L: NEC MPLC0730L3R3 22 1.8V Step-Down Converter RUN/SS BOOST ON OFF LT1913 RT 16.9k PG SYNC FB 78.7k GND f = 500kHz V OUT 1.8V 3.5A L 0.47μF 3.3μH D 127k 100k 47μF 1913 TA08 1913f ...
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... ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE LT1913 R = 0.115 0.38 ± 0.10 TYP 6 10 ...
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... High Effi ciency Step-Down DC/DC Converter Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 1.2V Step-Down Converter OFF RUN/SS BOOST LT1913 RT 17k PG SYNC FB 78.7k GND f = 500kHz COMMENTS V : 5.5V to 60V TSSOP16/E Package V : 3.6V to 36V ...