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LTC3557 Datasheet(PDF) 9 Page - Linear Technology |
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LTC3557 Datasheet(HTML) 9 Page - Linear Technology |
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9 / 28 page  LTC3557/LTC3557-1 9 35571fc PIN FUNCTIONS TYPICAL PERFORMANCE CHARACTERISTICS T A = 25°C unless otherwise specified 400mA Step-Down Switching Regulator Feedback Voltage vs Output Current Step-Down Switching Regulator Start-Up Waveform ILIM0, ILIM1 (Pins 1, 2): Input Current Control Pins. ILIM0 and ILIM1 control the input current limit. See Table 1. Both pins are pulled low by a weak current sink. WALL (Pin 3): Wall Adapter Present Input. Pulling this pin above 4.3V will disconnect the power path from VBUS to VOUT. The ACPR pin will also be pulled low to indicate that a wall adapter has been detected. LDO3V3 (Pin 4): Always On 3.3V LDO Output. The LDO3V3 pin provides a regulated, always-on 3.3V supply voltage. This pin gets its power from VOUT. It may be used for light loads such as a real-time clock or housekeeping microprocessor. A 1μF capacitor is required from LDO3V3 to ground if it will be called upon to deliver current. If the LDO3V3 output is not used it should be disabled by connecting it to VOUT. SW1 (Pin 5): Power Transmission (Switch) Pin for Step-Down Switching Regulator 1. VIN1 (Pin 6): Power Input for Step-Down Switching Regulator 1. This pin will generally be connected to VOUT. FB1 (Pin 7): Feedback Input for Step-Down Switching Regulator 1. This pin servos to a fixed voltage of 0.8V when the control loop is complete. MODE (Pin 8): Low Power Mode Enable. When this pin is pulled high, the three step-down switching regulators are set to low power Burst Mode operation. EN1 (Pin 9): Logic Input Enables Step-Down Switching Regulator 1. EN2 (Pin 10): Logic Input Enables Step-Down Switching Regulator 2. EN3 (Pin 11): Logic Input Enables Step-Down Switching Regulator 3. FB3 (Pin 12): Feedback Input for Step-Down Switching Regulator 3. This pin servos to a fixed voltage of 0.8V when the control loop is complete. FB2 (Pin 13): Feedback Input for Step-Down Switching Regulator 2. This pin servos to a fixed voltage of 0.8V when the control loop is complete. RST2(Pin14):Thisisanopen-drainoutputwhichindicates that step-down switching regulator 2 has settled to its final value. It can be used as a power on reset for the primary microprocessor or to enable the other buck regulators for supply sequencing. SW2 (Pin 15): Power Transmission (Switch) Pin for Step-Down Switching Regulator 2. 600mA Step-Down Switching Regulator Feedback Voltage vs Output Current OUTPUT CURRENT (mA) 0.78 0.84 0.85 0.77 0.76 0.83 0.80 0.82 0.81 0.79 0.1 10 100 1000 35571 G22 0.75 1 3.8V 5V Burst Mode OPERATION PULSE SKIP OUTPUT CURRENT (mA) 0.78 0.84 0.85 0.77 0.76 0.83 0.80 0.82 0.81 0.79 0.1 10 100 1000 35571 G23 0.75 1 3.8V 5V Burst Mode OPERATION PULSE SKIP VOUT2 50mV/DIV(AC) VOUT1 1V/DIV IL1 200mA/DIV 0V EN1 0mA 35571 G24 100μs/DIV VOUT2 = 1.2V IOUT2 = 50mA MODE = 1 ROUT1 = 8Ω |
Similar Part No. - LTC3557_15 |
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Similar Description - LTC3557_15 |
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