LTC4278CDKD#PBF Linear Technology, LTC4278CDKD#PBF Datasheet
LTC4278CDKD#PBF
Specifications of LTC4278CDKD#PBF
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LTC4278CDKD#PBF Summary of contents
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... The LTC4278 is available in a space saving 32-pin DFN package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5841643 ...
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... LTC4278C-1 ................................................. 0°C to 70°C LTC4278I-1 ..............................................–40°C to 85°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LTC4278CDKD#PBF LTC4278CDKD#TRPBF LTC4278IDKD#PBF LTC4278IDKD#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. ...
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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER Interface Controller (Note 4) Operating Input Voltage Signature Range Classifi cation Range ON Voltage OFF Voltage Overvoltage Lockout ON/OFF Hysteresis Window Signature/Class Hysteresis Window Reset Threshold Supply Current Supply ...
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LTC4278 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER PWM Controller (Note 10) Power Supply V Operating Range CC V Supply Current ( Shutdown Current CC Feedback Amplifi er Feedback Regulation Voltage (V ...
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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER Load Compensation Load Compensation to V Offset Voltage SENSE Feedback Pin Load Compensation Current UVLO Function UVLO Pin Threshold (V ) UVLO UVLO Pin Bias Current Note 1: Stresses ...
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LTC4278 TYPICAL PERFORMANCE CHARACTERISTICS Input Current vs Input Voltage 25k Detection Range 0 25°C A 0.4 0.3 0.2 0 VOLTAGE (V) PORTP 4278 G01 Signature Resistance vs Input Voltage 28 ΔV ...
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TYPICAL PERFORMANCE CHARACTERISTICS V Shutdown Current CC vs Temperature UVLO 14V –50 – 100 TEMPERATURE (°C) 4278 G02 SENSE Fault ...
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LTC4278 TYPICAL PERFORMANCE CHARACTERISTICS Feedback Amplifi er Source and Sink Current vs Temperature 70 SOURCE CURRENT SINK CURRENT 1. 100 –50 – TEMPERATURE ...
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TYPICAL PERFORMANCE CHARACTERISTICS Minimum PG On-Time vs Temperature 340 R = 158k tON(MIN) 330 320 310 300 290 280 270 260 –50 – 100 125 TEMPERATURE (°C) 4278 G28 PG Delay Time vs Temperature 300 250 ...
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LTC4278 PIN FUNCTIONS SHDN (Pin 1): Shutdown Input. Use this pin for auxiliary power application. Drive SHDN high to disable LTC4278 operation and corrupt the signature resistance. If unused, tie SHDN PORTN T2P (Pin 2): Type 2 ...
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PIN FUNCTIONS Information section for details. This pin is used for the UVLO function of the switching regulator. The PD interface section has an internal UVLO. – + SENSE , SENSE (Pins 19, 20): Current Sense Inputs. These pins are ...
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LTC4278 BLOCK DIAGRAM SHDN 1 T2P 2 R CLASS PORTN 5 V PORTN 1.237V REFERENCE (V DISABLE + 0.8V – UVLO 18 OSC 15 OSCILLATOR SYNC 13 t ...
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APPLICATIONS INFORMATION OVERVIEW Power over Ethernet (PoE) continues to gain popularity as more products are taking advantage of having DC power and high speed data available from a single RJ45 connector. As PoE continues to grow in the marketplace, powered ...
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LTC4278 APPLICATIONS INFORMATION Table 1. LTC4278 Modes of Operation as a Function of Input Voltage V –V (V) LTC4278 MODES OF OPERATION PORTP PORTN 0V to 1.4V Inactive (Reset After 1st Classifi cation Event) 1.5V to 9.8V 25k Signature Resistor ...
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APPLICATIONS INFORMATION SIGNATURE CORRUPT OPTION In some designs that include an auxiliary power option necessary to prevent a PD from being detected by a PSE. The LTC4278 signature resistance can be corrupted with the SHDN pin (Figure 3). ...
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LTC4278 APPLICATIONS INFORMATION 50 40 1st CLASS 30 2nd CLASS DETECTION V1 1st MARK 2nd MARK DETECTION V2 INRUSH 1st CLASS 2nd CLASS 40mA DETECTION V1 1st MARK 2nd MARK DETECTION INRUSH = dt ...
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APPLICATIONS INFORMATION To control the power-on surge currents in the system, the LTC4278 provides a fi xed inrush current, allowing C1 to ramp up to the line voltage in a controlled manner. The LTC4278 keeps the PD inrush current below ...
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LTC4278 APPLICATIONS INFORMATION PWRGD PIN WHEN SHDN IS INVOKED In PD applications where an auxiliary power supply invokes the SHDN feature, the PWRGD pin becomes high imped- ance. This prevents the PWRGD pin that is connected to the UVLO pin ...
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APPLICATIONS INFORMATION An input diode bridge must be rated above the maximum current the PD application will encounter at the tempera- ture the PD will operate. Diode bridge vendors typically call out the operating current at room temperature, but derate ...
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LTC4278 APPLICATIONS INFORMATION Classifi cation Resistor (R ) CLASS The R resistor sets the classifi cation load current, CLASS corresponding to the PD power classifi cation. Select the value of R from Table 2 and connect the resistor CLASS between ...
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... PoE power is already present. This confi guration also provides a seamless transition from PoE to auxiliary power when auxiliary power is applied, however, the removal of auxiliary power to PoE power is not seamless. Contact Linear Technology applications support for detail information on implementing a custom auxiliary power supply. IEEE 802.3at SYSTEM POWER-UP REQUIREMENT Under the IEEE 802 ...
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LTC4278 APPLICATIONS INFORMATION compensation circuitry. The logic block also contains circuitry to control the special dynamic requirements of fl yback control. For more information on the basics of current mode switcher/controllers and isolated fl yback converters see Application Note 19. ...
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APPLICATIONS INFORMATION LTC4278 FEEDBACK AMP 1.237V – + COLLAPSE DETECT ENABLE Figure 10a. LTC4278 Switching Regulator Feedback Amplifi er PRIMARY-SIDE MOSFET DRAIN VOLTAGE VOLTAGE SG VOLTAGE Figure 10b. LTC4278 Switching Regulator Timing ...
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LTC4278 APPLICATIONS INFORMATION to transformer leakage inductance. The latter causes a voltage spike on the primary side, not directly related to output voltage. Some time is also required for internal settling of the feedback amplifi er circuitry. In order to ...
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APPLICATIONS INFORMATION Assuming relatively fi xed power supply effi ciency, Eff, power balance gives Eff • P OUT IN V • Eff • V • I OUT OUT IN IN Average primary-side current is expressed in ...
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LTC4278 APPLICATIONS INFORMATION Note the use of the external feedback resistive divider ratio to set output voltage provides the user additional freedom in selecting a suitable transformer turns ratio. Turns ratios that are the simple ratios of small integers; e.g., ...
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APPLICATIONS INFORMATION A fi nal note—the susceptibility of the system to bistable behavior is somewhat a function of the load current/ voltage characteristics. A load with resistive—i.e V/R behavior—is the most apt to be bistable. Capacitive loads 2 ...
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LTC4278 APPLICATIONS INFORMATION when the peak design current is exceeded. This results in an abrupt increase in inductor ripple current and, consequently, output voltage ripple. Do not allow the core to saturate! The maximum peak primary current occurs at minimum ...
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APPLICATIONS INFORMATION Selecting the Load Compensation Resistor The expression for R was derived in the Operation CMP section as − R • SENSE = • • CMP + ESR R DS ...
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LTC4278 APPLICATIONS INFORMATION trace length and area to minimize stray capacitance and potential noise pick-up. You can synchronize the oscillator frequency to an external frequency. This is done with a signal on the SYNC pin. Set the LTC4278 frequency 10% ...
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APPLICATIONS INFORMATION Primary Gate Delay Time (PGDLY) Primary gate delay is the programmable time from the turn-off of the synchronous MOSFET to the turn-on of the primary-side MOSFET. Correct setting eliminates overlap between the primary-side switch and secondary-side syn- chronous ...
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LTC4278 APPLICATIONS INFORMATION If we wanted a V -referred trip point of 36V, with 1.8V IN (5%) of hysteresis (on at 36V, off at 34.2V): = 1.8V = 529k, use 523k R A 3.4μA 523k = = 18.5k, use 18.7k ...
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APPLICATIONS INFORMATION In further contrast to traditional current mode switchers, V pin ripple is generally not an issue with the LTC4269-1. CMP The dynamic nature of the clamped feedback amplifi er forms an effective track/hold type response, whereby the V ...
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LTC4278 APPLICATIONS INFORMATION Output Voltage Error Sources The LTC4278’s feedback sensing introduces additional minor sources of errors. The following is a summary list: • The internal bandgap voltage reference sets the reference voltage for the feedback amplifi er. The specifi ...
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APPLICATIONS INFORMATION C is calculated from the gate charge curve included MILLER on most MOSFET data sheets (Figure 16). MILLER EFFECT GATE CHARGE ( Figure 16. Gate Charge Curve The ...
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LTC4278 APPLICATIONS INFORMATION Capacitor Selection In a fl yback converter, the input and output current fl ows in pulses, placing severe demands on the input and output fi lter capacitors. The input and output fi lter capacitors are selected based ...
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... PORTP internal MOSFET and may cause permanent damage to the LTC4278. In order to minimize switching noise and improve output load regulation, connect the GND pin of the LTC4278 directly SwitcherCAD is a registered trademark of Linear Technology Corporation. LTC4278 CLASS , PORTP . The PORTN ...
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LTC4278 APPLICATIONS INFORMATION to the ground terminal of the V CC the bottom terminal of the current sense resistor and the ground terminal of the input capacitor, using a ground plane with multiple vias. Place the V capacitor immediately CC ...
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... ALL DIMENSIONS ARE IN MILLIMETERS Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. DKD Package 32-Lead Plastic DFN (7mm × ...
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... High Power PD with Synchronous No-Opto Flyback Controller LTC4269-1 IEEE 802.3af/IEEE 802.3at PD with Synchronous No-Opto Flyback Controller LTC4269-2 IEEE 802.3af/IEEE 802.3at PD with Synchronous Forward Controller ThinSOT is a trademark of Linear Technology Corporation. Linear Technology Corporation 40 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● COMMENTS ...