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LTC4418 - Dual Channel Prioritized PowerPath Controller

LTC4418 - Dual Channel Prioritized PowerPath Controller
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LTC4418 - Dual Channel Prioritized PowerPath Controller - 1

LTC4418 Dual Channel Prioritized PowerPath Controller FEATURES Selects Highest Priority Supply from Two Inputs nn Blocks Reverse and Cross Conduction Currents nn Wide Operating Voltage Range: 2.5V to 40V nn –42V Protection Against Reverse Connection nn 60V Tolerant V1, V2 Inputs nn Adjustable Input Validation Time nn Fast Switchover Minimizes Output Voltage Droop nn Low 26µA Operating Current nn ±1.5% Input Overvoltage/Undervoltage Protection nn Adjustable Overvoltage/Undervoltage Hysteresis nn Cascadable for Additional Input Supplies nn 20-Lead 4mm × 4mm QFN Package The LTC®4418 connects one of two valid power supplies to a common output based on priority and validity. Priority is defined by pin assignment, with V1 assigned the higher priority and V2 the lower priority. A power supply is defined as valid when its voltage has been within its overvoltage (OV) and undervoltage (UV) window continuously for at least the configured validation time. If the highest priority valid input falls out of the OV/UV window, the channel is immediately disconnected and the other valid input is connected to the common output. Multiple LTC4418s, as well as triple channel LTC4417s, can be cascaded to provide switchover between more than two inputs. The LTC4418 incorporates fast non-overlap switching circuitry to prevent both reverse and cross conduction while minimizing output droop. The gate driver includes a 6V clamp to protect external MOSFETs. A controlled soft-start feature minimizes start-up inrush current. Open drain VALID outputs indicate the input supplies have been within their OV/UV window for the duration of the validation time. The validation time can be disabled or adjusted using an external capacitor. APPLICATIONS Industrial Handheld Instruments High Availability Systems nn Battery Backup Systems nn Servers and Computer Peripherals nn nn L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and ThinSOT and PowerPath are trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. Priority Switching from V1 to V2

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 2

UF PACKAGE 20-LEAD (4mm x 4mm) PLASTIC QFN Tjmax = 150°C, 0ja = 47°C/W 0jc = 4.5°C/W EXPOSED PAD (PIN 21), PCB GND CONNECTION OPTIONAL ORDER INFORMATION http://www.linear.com/product/LTC4418#orderinfo LEAD FREE FINISH Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container For more information on lead free part marking, go to: http://www.linearcom/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit...

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 4

Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All currents into pins are positive; all voltages are referenced to GND unless otherwise specified. Note 3: Specification represents the diode-OR’d current of V1 or V2 input supplies. Current is split evenly if both supplies are equal. Note 4: UV1 or UV2 driven below VTH. Time is measured from respective rising edge G1 crossing VS1 - 3V or G2 crossing VS2 - 3V...

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 5

Total Shutdown Supply Current vs Supply Voltage IV1> IV2> ivout ALL SUPPLY VS AND VOUT PINS CONNECTED TOGETHER Gate Drive Voltage vs Temperature TEMPERATURE (°C) 4418 G04 Gate Pull-Down Current GATE VOLTAGE (V) 4418G07

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 6

OV, UV Hysteresis Current Configuration INTVcc vs Input Voltage (V1, V2, VouT) 4.0 3.5 Deglitched Connection VouT Switching from Higher to Lower Voltage VouT Switching from Lower to Higher Voltage with Inrush Current Limiting Circuitry Reverse Voltage Blocking V2, Vqut 5V/DIV V1 5V/DIV

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 7

Pin Funcnons TMR (Pin 1): Validation Timer. Attach an external capacitor between TMR and GND of at least 100pF to set a Validation Time of 16ms/nF for both channels. Connect TMR to INTVcc to set a minimum validation time of 3.5ps (Fast Mode). Do not leave open. UV1, UV2 (Pins 2, 4): Undervoltage Comparator Inputs. Falling voltages below 1V (VTH) trigger an undervoltage event, invalidating the respective input supply channel. Connect UV1 and UV2 to a resistive divider between the respective V1 and V2 and ground to achieve the desired undervoltage threshold. The comparator hysteresis can be...

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 8

LTC4418 PIN FUNCTIONS EN (Pin 18): Channel Enable Input. EN is a 40V input that allows the user to quickly connect and disconnect channels without resetting the OV/UV Validation timer. This feature is essential in cascading applications. When below 1V (VEN(TH)), both external P-channel MOSFETs are driven off by pulling G1 and G2 to their respective VS1 and VS2. When above VEN(TH), the highest valid priority channel is connected to the output. EN is pulled to INTVCC with a 3.2µA current source (ICTRL) and can be pulled up externally to a maximum voltage of 40V. Connect to INTVCC when not...

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 9

LTC4418 BLOCK DIAGRAM INTVCC 3.2µA INTVCC SHDN V1 DISABLE GATEDRIVERS AND RESET VALIDATION TIMER INTVCC DISABLE GATEDRIVERS CAS HYSTERESIS IEXT PRIORITIZED NONOVERLAP CONTROL LOGIC For more information www.linea

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 11

LTC4418 OPERATION The LTC4418 is an intelligent 40V dual channel PowerPath™ switch that automatically connects one of two input supplies to a common output based on a channel’s priority and validity. Channel 1 is defined to be higher priority than Channel 2 regardless of voltage levels. A channel’s validity is user defined by a set of undervoltage (UV) and overvoltage (OV) comparators biased with a resistive divider off of the channel’s input. Connection is made by enhancing external back-to-back P-channel MOSFETs. Unlike a diode-OR, which always passes the highest supply voltage to the...

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LTC4418 - Dual Channel Prioritized PowerPath Controller - 12

LTC4418 APPLICATIONS INFORMATION PowerPath controllers are designed to connect one of several input supplies to a common output based on their priority and validity. The highest priority supply may not necessarily be the highest in voltage. While the application appears simple at first glance there are a few issues that must be accounted for when building an application. One issue is input supply inrush current during a channel switchover that occurs when charging a low ESR output capacitor. Inrush current dissipates significant power in the external P-channel MOSFETs. It also causes input...

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