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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump

LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump
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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 1

LTC3255 Wide VIN Range Fault Protected 50mA Step-Down Charge Pump DESCRIPTION FEATURES Input Voltage Range: 4V to 48V n Adjustable Regulated Output: 2.4V to 12.5V n Output Current: 50mA Maximum n 16μA Quiescent Current in Regulation at No Load n Input Fault Protection from –52V to 60V n Multimode Charge Pump (2:1, 1:1) with Automatic Mode Switching Maintains Regulation Over Wide VIN Range n Input Voltage Shunt Mode for Current-Fed Applications n Power Good Output n Overtemperature and Short-Circuit Protection n Operating Junction Temperature: 150°C Maximum n Thermally Enhanced 10-Lead MSOP and 10-Lead (3mm × 3mm) DFN packages n APPLICATIONS Industrial Control, Factory Automation, Sensors, and SCADA Systems n Housekeeping Power Supplies n Current-Boosting Voltage Regulators for 4mA to 20mA Current Loops n The LTC®3255 is a switched-capacitor step-down DC/DC converter that produces a regulated output (2.4V to 12.5V adjustable) from a 4V to 48V input. In applications where the input voltage exceeds twice the output voltage, 2:1 capacitive charge pumping extends output current capability beyond input supply current limits. At no load, Burst Mode® operation cuts VIN quiescent current to 16µA. With its integrated VIN shunt regulator, the LTC3255 excels in 4mA to 20mA current loop applications. The device enables current multiplication; a 4mA input current can power a 7.4mA load continuously. Alternatively, the LTC3255 serves as a higher efficiency replacement for linear regulators and provides a space-saving inductorfree alternative to buck DC/DC converters. The LTC3255 withstands reverse-polarity input supplies and output short-circuits without damage. Safety features including current limit and overtemperature protection further enhance robustness. The LTC3255 is available in thermally enhanced 10-lead MSOP and low profile 3mm × 3mm 10-lead DFN packages. L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Available Output Current vs Input Current 7.4mA DC Supply from 4mA to 20mA Current Loop 40 PGOOD BIAS AVAILABLE OUTPUT CURRENT (mA) AVAILABLE IOUT INCREASED IOUT CAPABILITY INPUT CURRENT

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 2

LTC3255 ABSOLUTE MAXIMUM RATINGS C+ 1 VOUT 2 FB 3 SHUNT 4 PGOOD 5 MSE PACKAGE 10-LEAD PLASTIC MSOP DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN TJMAX = 150°C, θJA = 43°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB TJMAX = 150°C, θJA = 40°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on...

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 3

The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C. VIN = 12V unless otherwise noted. (Notes 2, 3) SYMBOL VIN Undervoltage Lockout Threshold with Shunt Disabled VIN Rising, SHUNT = GND Hysteresis, SHUNT = GND VIN Undervoltage Lockout Threshold with Shunt Enabled Input Voltage Range (Note 7) Output Voltage Range VIN Rising, SHUNT= BIAS Hysteresis, SHUNT= BIAS VIN Quiescent Current EN Low EN High, SHUNT = GND EN High, SHUNT = BIAS Shutdown Enabled, Output in Regulation Enabled, Output in Regulation...

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 4

LTC3255 TYPICAL PERFORMANCE CHARACTERISTICS Input Operating Current vs Input Voltage 50 Input Shutdown Current vs Input Voltage Input Operating Current vs Temperature TA = 25°C, unless otherwise noted. IOUT = 1mA VOUT = 5V SHUNT = GND FB Pin Regulation Voltage vs Input Voltage (IOUT = 50mA) FB Pin Regulation Voltage vs Temperature 1.224 IOUT = 50mA VOUT = 5V SHUNT = GND FB Pin Regulation Voltage vs Input Voltage (IOUT = 1mA) TRANSITION REGION TRANSITION REGION VOUT = 2.5V VOUT = 3.3V VOUT = 5V VOUT = 12V Typical Minimum VIN – 2 • VOUT Compliance Required for Shunt Mode Operation Operating...

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 5

LTC3255 TYPICAL PERFORMANCE CHARACTERISTICS 3.3VOUT Efficiency vs Input Voltage at 50mA Load 100 5VOUT Efficiency vs Input Voltage at 50mA Load 100 Output Ripple 5VOUT Efficiency vs Output Current TA = 25°C, unless otherwise noted. 2.5V Output Voltage vs Falling Input Voltage Load Transient IOUT VIN = 12V VOUT = 3.3V IOUT = 5mA 3.3V Output Voltage vs Falling Input Voltage 3.40 5V Output Voltage vs Falling Input Voltage 5.10 12V Output Voltage vs Falling Input Voltage 12.25

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 6

LTC3255 PIN FUNCTIONS C+ (Pin 1): Flying Capacitor Positive Connection. This pin must not be driven externally. VOUT (Pin 2): Charge Pump Output Voltage. FB (Pin 3): Feedback pin for setting the regulated output voltage, usually connected to VOUT through an external resistor divider. In operation, the LTC3255 servos the FB pin to 1.2V by transferring charge from VIN to VOUT. SHUNT (Pin 4): Configuration pin that must connect to either the BIAS or GND pins to enable or defeat, respectively, the LTC3255’s shunt regulator feature. Connect this pin to either BIAS or GND on the circuit board...

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 7

LTC3255 SIMPLIFIED BLOCK DIAGRAM 10 SHUNT CONTROL CHARGE PUMP CONTROL

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 8

LTC3255 APPLICATIONS INFORMATION General Operation Regulation Loop The LTC3255 uses switched-capacitor-based DC/DC conversion to provide efficiency advantages associated with inductor-based circuits together with the cost and simplicity advantages of linear regulators. No inductors are required. The LTC3255 uses an internal switch network and fractional conversion ratios to achieve high efficiency and regulation over widely varying VIN and output load conditions. A defeatable VIN shunt regulator allows the LTC3255 to operate with current-fed VIN supplies, such as 4mA to 20mA current loops....

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LTC3255 - Wide VIN Range Fault Protected 50mA Step-Down Charge Pump - 9

LTC3255 APPLICATIONS INFORMATION The LTC3255 has thermal protection that will shut down the device if the junction temperature exceeds the overtemperature threshold (typically 175°C). Thermal shutdown is included to protect the IC in cases of excessively high ambient temperatures, or in cases of excessive power dissipation inside the IC. The charge transfer will reactivate once the junction temperature drops back to approximately 165°C. When the thermal protection is active, the junction temperature is beyond the specified operating range. Thermal protection is intended for momentary...

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