ltc3873 Linear Technology Corporation, ltc3873 Datasheet
ltc3873
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ltc3873 Summary of contents
Page 1
... Using a 9.3V internal shunt regulator, the LTC3873 can be powered from a high input voltage through a resistor or it can be powered directly from a low impedance DC voltage less. The LTC3873 is available in 8-lead ThinSOT and 2mm x 3mm DFN packages. PARAMETER V CC ...
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... TS8 Package ..................................................... 300° RUN/ NGATE EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB ORDER PART NUMBER LTCSN LTC3873EDDB The ● denotes the specifi cations which apply over the full operating = 25° unless otherwise noted. (Note CONDITIONS ...
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... IN IN RUN/SS Note 4: The dynamic input supply current is higher due to power MOSFET gate charging (Q Note 5: The LTC3873 is tested in a feedback loop which servos V the reference voltage with the I range (0.7V ≤ V Note 6: Rise and fall times are measured at 10% and 90% levels 5.6V ...
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... LTC3873 TYPICAL PERFORMANCE CHARACTERISTICS Shutdown Mode (V) IN 3873 G04 RUN Threshold vs Temperature 1.0 0.9 0.8 0.7 0.6 0.5 –60 –40 – TEMPERATURE (°C) Frequency vs Temperature 250 230 210 190 170 150 –60 –40 –20 ...
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... Exposed Pad (NA/Pin 9): Ground. Must be soldered to PCB for electrical contact and rated thermal performance 9.5V CC SHUNT 1.2V REGULATOR + I TH BUFFER – CURRENT LIMIT CLAMP ERROR AMPLIFIER – LTC3873 GND SW SLOPE COMPENSATION – + IPRG CURRENT COMPARATOR I LIM 200kHz OSCILLATOR AND LATCH MAX DUTY CYCLE NGATE SWITCHING ...
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... Figure 2. SW Pin (Internal Sense Pin) Connection for Sensing Resistor 6 The LTC3873 can be used either by sensing the voltage drop across the power MOSFET or by connecting the SW pin to a conventional sensing resistor in the source of the power MOSFET. Sensing the voltage across the power MOSFET maximizes converter effi ...
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... LTC3873—see the section, V RUN/SS pin can be driven below V SHDN to force the LTC3873 into shutdown. When the chip is off, the input supply current is typically only 55μA. Soft-Start Leave the RUN/SS pin open to use the internal 3.3ms soft- start ...
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... Figure 5 shows a different fl yback converter bias power strategy for a case in which neither the input or the output is suitable for providing the bias power to the LTC3873. The trickle charger is identical to that described in the prior paragraph. However, the fl yback transformer has an 8 additional bias winding to provide bias power ...
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... VCC 0.1µF 8.2V Figure 6 Slope Compensation The LTC3873 has built-in internal slope compensation to stabilize the control loop against sub-harmonic oscillation. It also provides the ability to externally increase slope compensation by injecting a ramping current out of its SW pin into an external slope compensation resistor (R Figure 4). This current ramp starts at zero right after the NGATE pin has been set high. The current rises linearly towards a peak of 20µ ...
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... However, remember that this will limit the primary-to- secondary breakdown voltage, so bifi lar winding is not always practical. Power MOSFET Selection The power MOSFET serves two purposes in the LTC3873: it represents the main switching element in the power path and its R represents the current sensing element DS(ON) for the control loop ...
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... MAX Duty Cycle Considerations The LTC3873 imposes a maximum duty cycle limit of 80% typical. For a fl yback converter, the maximum duty cycle prevents the transformer core from saturation boost converter application, however, it sets a limit on the maximum step-up ratio or maximum output voltage ...
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... V SEPIC Converter IN OUT T1 4.56µH BH510-1009 BH ELECTRONICS • • 15V + 10µF 100µF ×3 20V 2 3 10µF 25V 301Ω LTC3873 Si4840 PRG 7 I RUN/ 1. GND NGATE 4.7µF 0.1µF 3873 TA05 UPS840 V OUT 12V ...
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... UPS840 10 FDC2512 2.2Ω 2 0.068Ω 0.1µF 4.7µF 1210 AND 6.8k 0805 NEC PS2801-1 BAT760 2200pF 250V AC LTC3873 V OUT 3.3V 3A 100µF 6.3V ×3 1 BAT54CWT1G 3 1µF OPT LT4430 274Ω 100k V OPTO 22nF IN 3.01k 2 5 GND COMP ...
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... LTC3873 PACKAGE DESCRIPTION 0.52 MAX 3.85 MAX 2.62 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.20 BSC DATUM ‘A’ 0.30 – 0.50 REF NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6 ...
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... LTC DWG # 05-08-1702 Rev B) 0.70 ±0.05 PACKAGE OUTLINE 0.50 BSC 2.20 ±0.05 (2 SIDES 0.115 3.00 ±0.10 TYP R = 0.05 (2 SIDES) TYP 2.00 ±0.10 (2 SIDES) 0.56 ± 0.05 (2 SIDES) 4 0.25 ± 0.05 0.75 ±0.05 0 – 0.05 BOTTOM VIEW—EXPOSED PAD LTC3873 0.40 ± 0. PIN 0.20 OR 0.25 × 45° CHAMFER 1 (DDB8) DFN 0905 REV B 0.50 BSC 2.15 ±0.05 (2 SIDES) 3873f 15 ...
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... LTC3805 Adjustable Frequency Flyback Controller LTC3825 Isolated No-Opto Synchronous Flyback Controller LTC3837 Isolated No-Opto Synchronous Flyback Controller LTC3872 No R Boost Controller SENSE LTC3873 Constant Frequency Boost/Flyback/SEPIC SENSE Controller Linear Technology Corporation 16 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900 FAX: (408) 434-0507 ...