LTC4257CDD-1#TRPBF Linear Technology, LTC4257CDD-1#TRPBF Datasheet
LTC4257CDD-1#TRPBF
Specifications of LTC4257CDD-1#TRPBF
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LTC4257CDD-1#TRPBF Summary of contents
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... Power Sourcing Equipment (PSE) applications. The LTC4257-1 is available in the 8-pin SO and low profile (3mm × 3mm) DFN packages. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Powered Device (PD) LTC4257-1 5µ ...
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... SIGDISA 6 PWRGD V 5 OUT EXPOSED PAD TO BE SOLDERED TO ELECTRICALLY ISOLATED PCB HEATSINK S8 PART MARKING ORDER PART NUMBER 42571 LTC4257CDD-1 4257I1 LTC4257IDD-1 http://www.linear.com/leadfree/ The ● denotes the specifications which apply over the full operating = 25°C. (Note 3) A CONDITIONS Voltage with Respect to GND Pin (Notes – ...
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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER V Signature Disable IH High Level Input Voltage V Signature Disable IL Low Level Input Voltage R Signature Disable INPUT Input Resistance V Power Good Output Low Voltage PG_OUT ...
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LTC4257 TYPICAL PERFOR A CE CHARACTERISTICS Input Current vs Input Voltage 25k Detection Range 0 25°C A 0.4 0.3 0.2 0 –4 –6 –8 –10 –2 INPUT VOLTAGE (V) 4357 G01 Input Current vs ...
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CTIO S NC (Pin 1): No Internal Connection. R (Pin 2): Class Select Input. Used to set the current CLASS value the LTC4257-1 maintains during classification. Con- nect a resistor between R and V CLASS ...
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LTC4257 APPLICATIO S I FOR ATIO The LTC4257-1 is intended for use as the front end of a Powered Device (PD) adhering to the IEEE 802.3af standard. The LTC4257-1 includes a trimmed 25k signature resistor, classification current source, ...
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U U APPLICATIO S I FOR ATIO summarized in Table 1. These various modes satisfy the requirements defined in the IEEE 802.3af specification. The input voltage is applied to the V reference to the GND pin. This input voltage is ...
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LTC4257 APPLICATIO S I FOR ATIO The power applied allowed to use either of two polarities and the PD must be able to accept this power common to install a diode ...
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U U APPLICATIO S I FOR ATIO specification. The LTC4257-1 is compatible with the IEEE 802.3af standard and also works with the obsolete Mea- sured Voltage method. In the Measured Current method (Figure 4), the PSE presents a fixed voltage ...
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LTC4257 APPLICATIO S I FOR ATIO Undervoltage Lockout The IEEE specification dictates a maximum turn-on volt- age of 42V and a minimum turn-off voltage of 30V for the PD. In addition, the PD must maintain large on-off hyster- ...
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U U APPLICATIO S I FOR ATIO accomplished by a dual level current limit. At turn on before C1 is charged, the LTC4257-1 current limit is set to the low level. After C1 is charged up and the V voltage ...
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LTC4257 APPLICATIO S I FOR ATIO If a sudden increase in voltage appears on the input line, this voltage step will be transferred through capacitor C1 and appear across the power MOSFET. The response of the LTC4257-1 will ...
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U U APPLICATIO S I FOR ATIO the overtemperature trip point. When the die cools down below the trip point, classification current is enabled again. If the PD is designed to operate at a high ambient tempera- ture and with ...
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LTC4257 APPLICATIO S I FOR ATIO The IEEE standard includes an AC impedance requirement in order to implement the AC disconnect function. Capaci- tor C14 in Figure 8 is used to meet this AC impedance requirement. A 0.1µF ...
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U U APPLICATIO S I FOR ATIO RJ45 + – – SPARE – SPARE 8 ISOLATED WALL TRANSFORMER OPTION 2: AUXILARY POWER INSERTED AFTER LTC4257-1 WITH ...
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LTC4257 APPLICATIO S I FOR ATIO that the transformer maintain the voltage between 38V and 57V to keep the LTC4257-1 in its normal operating range. The third option has the advantage of automatically dis- abling the 25k signature ...
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U U APPLICATIO S I FOR ATIO Signature Disable Interface To disable the 25k signature, connect the SIGDISA pin to the GND pin. Alternately, SIGDISA can be driven high with respect example of a signature disable ...
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LTC4257 APPLICATIO S I FOR ATIO 42571fb ...
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... RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...
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... Quad IEEE 802.3af Power over Ethernet Controller LTC4259A-1 Quad IEEE 802.3af Power over Ethernet Controller LTC4267 IEEE 802.3af PD Interface Controller with Integrated Switching Regulator Burst Mode is a registered trademark of Linear Technology Corporation Linear Technology Corporation 20 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● ...