LTC4267IGN-1#PBF Linear Technology, LTC4267IGN-1#PBF Datasheet
LTC4267IGN-1#PBF
Specifications of LTC4267IGN-1#PBF
Available stocks
Related parts for LTC4267IGN-1#PBF
LTC4267IGN-1#PBF Summary of contents
Page 1
... Wireless Access Points ■ Security Cameras ■ Power over Ethernet , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator DESCRIPTIO ® ...
Page 2
... Junction Temperature ........................................... 150°C Storage Temperature Range ...................–65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LTC4267CGN-1#PBF LTC4267CGN-1#TRPBF LTC4267IGN-1#PBF LTC4267IGN-1#TRPBF LEAD BASED FINISH TAPE AND REEL LTC4267CGN-1 LTC4267CGN-1#TR LTC4267IGN-1 LTC4267IGN-1#TR Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. ...
Page 3
ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T SYMBOL PARAMETER V P Shunt Regulator Voltage CLAMP1mA VCC V V – V Margin MARGIN CLAMP1mA TURNON I V Supply Current when ON VPORTN_ON PORTN I P Supply Current PVCC_ON ...
Page 4
LTC4267-1 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T SYMBOL PARAMETER t NGATE Drive Rise Time RISE t NGATE Drive Fall Time FALL V Peak Current Sense Voltage IMAX I Peak Slope Compensation Output Current SLMAX t Soft-Start ...
Page 5
W U TYPICAL PERFOR A Input Current vs Input Voltage 25k Detection Range Input Current vs Input Voltage Power Good Output Low Voltage vs Current CE CHARACTERISTICS Input Current vs Input Voltage Signature Resistance vs Input Voltage P Leakage Current ...
Page 6
LTC4267 TYPICAL PERFOR A CE CHARACTERISTICS Reference Voltage vs Temperature Oscillator Frequency vs Supply Voltage P Shunt Regulator Voltage vs VCC Temperature 6 Reference Voltage vs Supply Voltage P Undervoltage Lockout VCC Thresholds vs Temperature I Supply Current ...
Page 7
W U TYPICAL PERFOR A CE CHARACTERISTICS Start-Up I Supply Current vs PVCC Temperature Peak Current Sense Voltage vs Temperature I /RUN Shutdown Threshold vs TH Temperature Soft-Start Time vs Temperature LTC4267-1 I /RUN Start-Up Current Source TH vs Temperature ...
Page 8
LTC4267 CTIO S PGND (Pin 16): Switching Regulator Negative Supply. This pin is the negative supply rail for the switching regulator controller and must be tied /RUN (Pin 2): ...
Page 9
BLOCK DIAGRAM U U APPLICATIO S I FOR ATIO OVERVIEW The LTC4267-1 is partitioned into two major blocks: a Powered Device (PD) interface controller and a current mode fl yback switching regulator. The Powered Device (PD) interface is intended for ...
Page 10
LTC4267 APPLICATIO S I FOR ATIO avoid corrupting the 25k signature resistor while also sav- ing board space and cost. In addition, the inrush current limit requirement of the IEEE 802.3af standard can cause large transient power dissipation ...
Page 11
U U APPLICATIO S I FOR ATIO Series Diodes The IEEE 802.3af-defi ned operating modes for a PD refer- ence the input voltage at the RJ45 connector on the PD. The PD must be able to accept power of either ...
Page 12
LTC4267 APPLICATIO S I FOR ATIO Figure 3. 25k Signature Resistor with Disable Classifi cation Once the PSE has detected a PD, the PSE may option- ally classify the PD. Classifi cation provides a method for more effi ...
Page 13
U U APPLICATIO S I FOR ATIO the classifi cation current is reenabled. C1 will discharge through the PD circuitry and the P OUT impedance state. Figure 5. LTC4267-1 V Undervoltage Lockout PORTN Input Current Limit IEEE 802.3af specifi es ...
Page 14
LTC4267 APPLICATIO S I FOR ATIO Figure 6. LTC4267-1 Power Good the LTC4267-1 will attempt to quickly charge capacitor C1 using an internal secondary current limit circuit. In this scenario, the PSE current limit should provide the overall ...
Page 15
U U APPLICATIO S I FOR ATIO temperature exceeds the overtemperature trip point, the current is reduced to zero and very little power is dissi- pated in the part until it cools below the overtemperature set point. Once the LTC4267-1 ...
Page 16
LTC4267 APPLICATIO S I FOR ATIO Figure 8. LTC4267-1 Switching Regulator Start-Up/Shutdown State Diagram The undervoltage lockout mechanism on P the LTC4267-1 switching regulator from trying to drive the external N-Channel MOSFET with insuffi cient gate-to- source voltage. ...
Page 17
U U APPLICATIO S I FOR ATIO Diode Bridge IEEE 802.3af allows power wiring in either of two confi gu- rations: on the TX/RX wires or via the spare wire pairs in the RJ45 connector. The PD is required to ...
Page 18
LTC4267 APPLICATIO S I FOR ATIO Figure 10. PD Front End with Isolation Transformer, 2nd Schottky Diode Bridge designer should determine which power category the PD falls into and then select the appropriate value of R from Table ...
Page 19
U U APPLICATIO S I FOR ATIO Power Good Interface The ⎯ P ⎯ W ⎯ R ⎯ G ⎯ D signal is controlled by a high voltage, open- drain transistor. The designer has the option of using this signal ...
Page 20
LTC4267 APPLICATIO S I FOR ATIO the cable from causing damage. However, if the V pin is shorted to V inside the PD while the capacitor PORTP is charged, current will fl ow through the parasitic body diode ...
Page 21
U U APPLICATIO S I FOR ATIO collector resistor of the optoisolator can be selected for an increase in bandwidth at the cost of a reduction in gain of this stage. Output Transformer Design Considerations Since the external feedback resistor ...
Page 22
U U APPLICATIO S I FOR ATIO W U Figure 11. Typical LTC4267-1 Application Circuits LTC4267-1 42671f 22 ...
Page 23
LTC4267 APPLICATIO S I FOR ATIO to the LTC4267-1 switching regulator via its P (Figure 11). However, this arrangement is not inherently self-starting. Start-up is usually implemented by the use of an external “trickle-charge” resistor (R tion with ...
Page 24
LTC4267 APPLICATIO S I FOR ATIO Figure 12. Powering the LTC4267-1 Switching Regulator via the Shunt Regulator Figure 13. Powering the LTC4267-1 Switching Regulator with an External Preregulator preregulator consists of a series pass transistor Q1, zener diode ...
Page 25
U U APPLICATIO S I FOR ATIO In a nonisolated design, the LTC4267-1 incorporates an internal error amplifi er where the I a compensation point similar manner, a series RC network can be connected from I shown in ...
Page 26
LTC4267 APPLICATIO S I FOR ATIO Figure 16. Auxiliary Power Source for PD 42671f ...
Page 27
U U APPLICATIO S I FOR ATIO If auxiliary power is applied directly to the LTC4267-1 switching regulator (bypassing the LTC4267-1 PD inter- face), a different set of tradeoffs arise. In the confi guration shown in option 2, the wall ...
Page 28
LTC4267 APPLICATIO S I FOR ATIO For the LTC4267-1 switching regulator, the current loop through C1, T1 primary, Q1, and R careful layout attention. (Refer to Figure 11.) Because of the high switching current circulating in this loop, ...
Page 29
U TYPICAL APPLICATIO S Class 3 PD with 5V Nonisolated Power Supply LTC4267-1 • • 42671f 29 ...
Page 30
LTC4267-1 U TYPICAL APPLICATIO S 30 42671f ...
Page 31
... FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 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. ...
Page 32
... Quad IEEE 802.3af Power over Ethernet Controller LTC4263 Single IEEE 802.3af Power over Ethernet Controller LTC4267 IEEE 802.3af PD Interface with an Integrated Switching Regulator Burst Mode is a registered trademark of Linear Technology Corporation Linear Technology Corporation 32 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● ...