LTC3801 LINER [Linear Technology], LTC3801 Datasheet
LTC3801
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LTC3801 Summary of contents
Page 1
... The LTC3801 automatically switches into Burst Mode operation at light loads which enhances efficiency at low output current. In the LTC3801B, Burst Mode operation is disabled for lower output ripple at light loads. ...
Page 2
... J A Note 4: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. Note 5: The LTC3801/LTC3801B are tested in a feedback loop that servos V to the output of the error amplifier while maintaining I FB midpoint of the current limit range. and power ...
Page 3
... 808 804 800 796 792 788 (V) IN 3801 G07 Input DC Supply Current (SLEEP) vs Input Voltage (LTC3801 Only (V) IN 3801 G02 Shutdown Threshold vs Temperature ...
Page 4
... PGATE pin is held high. GND (Pin 2): Ground Pin. V (Pin 3): Receives the feedback voltage from an exter- FB nal resistor divider across the output CTIO AL DIAGRA UNDERVOLTAGE LOCKOUT 1 A (LTC3801) SHUTDOWN 2 A (LTC3801B) COMPARATOR I /RUN TH – 1 SHDN + SLEEP COMPARATOR – SLEEP ...
Page 5
... The main control loop is shut down by pulling the I pin to ground. Releasing the I TH internal 1 A current source ( LTC3801B) to charge up the external compensation network. When the I RUN pin voltage reaches approximately 0.6V, the main control loop is enabled and the I ...
Page 6
... For duty cycles less than 40%, the inductor’s peak current is determined by: I MAX However, for duty cycles greater than 40%, slope com- pensation begins and effectively reduces the peak Ripple for Front Page Circuit Using the LTC3801B (Burst Mode Operation Disabled) = 4.2V 5 s/DIV = 2.5V = 100mA rises through 0 ...
Page 7
... R is chosen based on the required output current. SENSE With the current comparator monitoring the voltage developed across R , the threshold of the compara- SENSE tor determines the inductor’s peak current. The output current the LTC3801 can provide is given by: 0 117 . I RIPPLE I OUT R ...
Page 8
... APPLICATIO S I FOR ATIO I = 0.4(I ). Remember, the maximum I RIPPLE OUT(MAX) occurs at the maximum input voltage. In Burst Mode operation on the LTC3801, the ripple current is normally set such that the inductor current is continuous during the burst periods. Therefore, the peak- to-peak ripple current must not exceed ...
Page 9
... This makes it advisable to further derate the capacitor choose a capacitor rated at a higher temperature than required. Several capacitors may be paralleled to meet the size or height requirements in the design. Due to the high operating frequency of the LTC3801/LTC3801B, ceramic capacitors can also be used for C manufacturer if there is any question. The selection of C series resistance (ESR) ...
Page 10
... W U Although all dissipative elements in the circuit produce losses, four main sources usually account for most of the losses in LTC3801/LTC3801B circuits: 1) LTC3801/ LTC3801B DC bias current, 2) MOSFET gate charge cur- 2 rent The V IN electrical characteristics, that excludes MOSFET driver and control currents. V which increases with V 2 ...
Page 11
... MIN (NOTE 4) 0.95 BSC 0.80 – 0.90 1.00 MAX 0.09 – 0.20 (NOTE 3) 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 LTC3801/LTC3801B V LTC3801/ OUT LTC3801B /RUN FB1 R1 D FB2 3801 F05 Figure 5. Foldback Current Limiting 2 ...
Page 12
... LTC3411/LTC3412 1.25/2.5A Monolithic Synchronous Step-Down Converter LTC3440 600mA (I ), 2MHz Synchronous Buck-Boost DC/DC Converter OUT trademark of Linear Technology Corporation. SENSE Linear Technology Corporation 12 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 LTC3801 No-Load 2. OUT 19 2. ...