IC PD/SYNC FORWARD CTRLR 32-DFN

LTC4269CDKD-2#PBF

Manufacturer Part NumberLTC4269CDKD-2#PBF
DescriptionIC PD/SYNC FORWARD CTRLR 32-DFN
ManufacturerLinear Technology
TypePower Over Ethernet (PoE)
LTC4269CDKD-2#PBF datasheet
 


Specifications of LTC4269CDKD-2#PBF

ApplicationsPower Interface Switch for Power Over Ethernet (PoE) DevicesVoltage - Supply14 V ~ 16 V
Operating Temperature0°C ~ 70°CMounting TypeSurface Mount
Package / Case32-DFNCurrent - Supply1.35mA
InterfaceIEEE 802.3afController TypePowered Device Interface Controller (PD)
Lead Free Status / RoHS StatusLead free / RoHS Compliant  
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FeaTures
25.5W IEEE 802.3at Compliant (Type-2) PD
n
+
PoE
2-Event Classification
n
IEEE 802.3at High Power Available Indicator
n
Integrated State-of-the-Art Synchronous Forward
n
Controller
– Isolated Power Supply Efficiency >94%
Flexible Auxiliary Power Interface
n
Superior EMI Performance
n
Robust 100V 0.7Ω (Typ) Integrated Hot Swap™
n
MOSFET
Integrated Signature Resistor, Programmable Class
n
Current, UVLO, OVLO and Thermal Protection
Short-Circuit Protection with Auto-Restart
n
Programmable Switching Frequency from
n
100kHz to 500kHz
Thermally Enhanced 7mm × 4mm DFN Package
n
applicaTions
IP Phones with Large Color Screens
n
Dual Radio 802.11n Access Points
n
PTZ Security Cameras
n
Typical applicaTion
PoE-Based Self-Driven Synchronous Forward Power Supply
10µH
+
10µF
2.2µF
~
+
54V FROM
DATA PAIR
~
~
+
54V FROM
~
SPARE PAIR
0.1µF
30.9
IEEE 802.3at High Power PD
and Synchronous Forward
Controller with AUX Support
DescripTion
The LTC
4269-2 is an integrated Powered Device (PD)
®
interface and power supply controller featuring 2-event
classification signaling, flexible auxiliary power op-
tions, and a power supply controller suitable for syn-
chronously rectified forward supplies. These features
make the LTC4269-2 ideally suited for an IEEE802.3at
PD application.
The PD controller features a 100V MOSFET that isolates
the power supply during detection and classification, and
provides 100mA inrush current limit. Also included are
power good outputs, an undervoltage/overvoltage lock-
out and thermal protection. The current mode forward
controller allows for synchronous rectification, resulting
in an extremely high efficiency, green product. Soft-start
for controlled output voltage start-up and fault recovery is
included. Programmable frequency over 100kHz to 500kHz
allows flexibility in efficiency vs size and low EMI.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Hot Swap, ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
1mH
33k
237k
0.1µF
V
CC
+
10.0k
10µF
10k
133
SD_V
PWRGD
V
S
OUT
SEC
IN
OUT
V
OC
PORTP
I
SENSE
LTC4269-2
R
COMP
CLASS
SHDN
FB
V
V
PORTN
REF
T2P V
PGND
GND BLANK DELAY
R
SS_MAXDC
NEG
OSC
82k
332k
158k
158k
TO
MICRO-
CONTROLLER
LTC4269-2
6.8µH
+
5.1
220µF
4.7nF
4.7nF
V
2k
CC
11.3k
1.5k
50m
10nF
33k
22k
1.2k
22.1k
TLV431
0.1µF
3.65k
0.22µF
42692 TA01
5V
5A
42692fb


LTC4269CDKD-2#PBF Summary of contents

  • Page 1

    ... Programmable frequency over 100kHz to 500kHz allows flexibility in efficiency vs size and low EMI. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and Hot Swap, ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ...

  • Page 2

    ... OSC V Source Current ..............................................10mA REF Operating Ambient Temperature Range LTC4269C-2 ............................................. 0°C to 70°C LTC4269I-2 ..........................................–40°C to 85°C orDer inForMaTion LEAD FREE FINISH TAPE AND REEL LTC4269CDKD-2#PBF LTC4269CDKD-2#TRPBF LTC4269IDKD-2#PBF LTC4269IDKD-2#TRPBF LEAD BASED FINISH TAPE AND REEL LTC4269CDKD-2 LTC4269CDKD-2#TR LTC4269IDKD-2 LTC4269IDKD-2#TR Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. ...

  • Page 3

    T PARAMETER Interface Controller (Note 5) Operating Input Voltage Signature Range Classification Range On Voltage Undervoltage Lockout Overvoltage Lockout ON/UVLO Hysteresis Window Signature/Class Hysteresis Window Reset Threshold Supply Current Supply Current at ...

  • Page 4

    LTC4269-2 elecTrical characTerisTics temperature range, otherwise specifications are at T PARAMETER SD_V Current SEC(ON) Current SD_V SEC(OFF) V IN(ON) V IN(OFF) V IN(HYST) V REF Output Voltage Line Regulation Load Regulation Oscillator Frequency, f OSC f OSC(MIN) f OSC(MAX) SYNC ...

  • Page 5

    T PARAMETER SOUT High Level SOUT Active Pull-Off in Shutdown SOUT to OUT (Rise) DELAY (t ) DELAY V DELAY OUT Driver OUT Rise Time OUT Fall Time OUT Clamp Voltage OUT ...

  • Page 6

    LTC4269-2 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 42692 G01 Signature Resistance vs Input Voltage 28 V ...

  • Page 7

    Typical perForMance characTerisTics Switching Frequency vs Temperature 245 230 215 200 185 170 155 –50 – 100 TEMPERATURE (°C) 42692 G10 Temperature OPEN 6.0 5.5 5.0 4.5 ...

  • Page 8

    LTC4269-2 Typical perForMance characTerisTics COMP Sink Current vs Temperature 12 1.4V COMP = 1.6V 10.0 7.5 5 –50 – 100 TEMPERATURE (°C) 42692 G19 I Maximum Threshold SENSE vs Temperature 240 COMP = 2.5V ...

  • Page 9

    Typical perForMance characTerisTics t : SOUT Rise to OUT Rise DELAY vs Temperature 200 150 R = 120k DELAY 100 40k DELAY 0 50 –50 – 100 TEMPERATURE (°C) 42692 G28 OUT : Max ...

  • Page 10

    LTC4269-2 pin FuncTions SHDN (Pin 1): Shutdown Input. Use this pin for auxiliary power application. Drive SHDN high to disable LTC4269-2 operation and corrupt the signature resistance. If unused, tie SHDN PORTN T2P (Pin 2): Type-2 PSE ...

  • Page 11

    FuncTions OC (Pin 19 accurate 107mV threshold, indepen- dent of duty cycle, for overcurrent detection and trigger of soft-start. Connect this pin directly to the sense resistor in the source of the external power MOSFET. DELAY ...

  • Page 12

    LTC4269-2 block DiagraMs SHDN 1 T2P CLASS V 5 PORTN V 6 PORTN START- INPUT CURRENT (ISTART OFF IN + – I HYST 10µA SD_V 0µA SD_V SEC + – ...

  • Page 13

    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 ...

  • Page 14

    LTC4269-2 applicaTions inForMaTion and current waveforms the LTC4269-2 may encounter with the various modes of operation summarized in Table 1. Table 1. LTC4269-2 Modes of Operation as a Function of Input Voltage V – V (V) LTC4269-2 MODES OF OPERATION ...

  • Page 15

    LTC4269-2 TO 14k PSE SHDN V PORTN SIGNATURE DISABLE Figure 3. 25k Signature Resistor with Disable also ceases operation for classification and turns off the internal Hot Swap FET. If this feature is not used, connect SHDN to ...

  • Page 16

    LTC4269-2 applicaTions inForMaTion when the PSE presents an input voltage between 15.5V to 20.5V and the LTC4269-2 presents a Class 4 load cur- rent. The PSE then drops the input voltage into the mark voltage range 10V, ...

  • Page 17

    LTC4269-2 V PORTP TO UNDERVOLTAGE PSE OVERVOLTAGE LOCKOUT CIRCUIT V V PORTN LTC4269-2 V – V POWER MOSFET PORTP PORTN 0V TO ON* OFF >ON* ON <UVLO* OFF >OVLO OFF *INCLUDES ON-UVLO HYSTERESIS ON THRESHOLD 36.1V UVLO THRESHOLD ...

  • Page 18

    LTC4269-2 applicaTions inForMaTion THERMAL PROTECTION The IEEE 802.3af/at specification requires withstand any applied voltage from 0V to 57V indefinitely. However, there are several possible scenarios where a PD may encounter excessive heating. During classification, excessive heating may ...

  • Page 19

    A silicon diode bridge can consume over 4% of the available power in some PD applications. Using Schottky diodes can help reduce the power loss with a lower forward voltage. A Schottky bridge may not be suitable for ...

  • Page 20

    ... Auxiliary power can be injected into the PD at several locations with priority chosen between PoE or auxiliary power sources. 0 These options come with various trade-offs and design considerations. Contact Linear Technology applications support for detailed information on implementing custom P auxiliary power sources. TO PD’s MICROPROCESSOR IEEE 802 ...

  • Page 21

    An additional output signal is included for synchronous rectifier control or active clamp control. A precision 107mV threshold senses overcurrent conditions and triggers soft- start for low stress short-circuit protection and control. The key functions of the LTC4269-2 ...

  • Page 22

    LTC4269-2 applicaTions inForMaTion An increase of voltage at the SD_V maximum duty cycle clamp to decrease. If SD_V resistively divided down from power supply input volt- age, a volt-second clamp is realized. To adjust the initial maximum duty cycle clamp, ...

  • Page 23

    Synchronizing A SYNC pin allows the LTC4269-2 oscillator to be synchro- nized to an external clock. The SYNC pin can be driven from a logic-level output, requiring less than 0.8V for a logic-level low and greater than 2.2V ...

  • Page 24

    LTC4269-2 applicaTions inForMaTion Programming Oscillator Frequency The oscillator frequency ( the LTC4269-2 is pro- OSC grammed using an external resistor, R between the R pin and GND. Figure 11 shows typical OSC resistor values. The ...

  • Page 25

    R = sense resistor in source of primary MOSFET ripple current in the output inductor L1 RIPPLE P number of transformer secondary turns number of transformer primary turns ...

  • Page 26

    LTC4269-2 applicaTions inForMaTion POWER SUPPLY INPUT VOLTAGE R1 ADAPTIVE DUTY CYCLE CLAMP INPUT MAX DUTY CYCLE CLAMP ADJUST INPUT *MINIMUM ALLOWABLE R IS 10k TO T GUARANTEE SOFT-START PULL-OFF Figure 15. Programming Maximum Duty ...

  • Page 27

    PROGRAMMABLE SYNCHRONOUS DELAY DELAY SOUT OUT SS_MAXDC FAULTS TRIGGERING SOFT-START V < 8.75V IN OR SD_V < 1.32V (UVLO) SEC OR OC > 107mV (OVERCURRENT) SOFT-START LATCH SET Figure 16. Timing Diagram SS_MAXDC SOFT-START EVENT TRIGGERED ...

  • Page 28

    LTC4269-2 applicaTions inForMaTion The time for SS_MAXDC to fall to a given voltage can be approximated as: SS_MAXDC(t )= FALL ( • [SS_MAXDC(DC) – DIS where net discharge current on C DIS C = ...

  • Page 29

    CHARGE V = 2.5V 35.7k 100k, C REF 0.45V. SS(MIN t(V = 0.8V) – t(V CHARGE SS SS Step 1: SS_MAXDC(DC) ...

  • Page 30

    LTC4269-2 applicaTions inForMaTion Example (3) Time For Maximum Duty Cycle Clamp to Reach Within X% of Target Value A maximum duty cycle clamp of 72% was calculated previ- ously in the section ‘Programming Maximum Duty Cycle Clamp’. The programmed value ...

  • Page 31

    Typical applicaTion LTC4269-2 (%) EFFICIENCY 42692fb  ...

  • Page 32

    LTC4269-2 package DescripTion 4.50 0.05 6.43 0.05 3.10 0.05 2.65 0.05 0.40 BSC 6.00 REF RECOMMENDED SOLDER PAD LAYOUT APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 7.00 0.10 PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF NOTE: ...

  • Page 33

    ... Undervoltage Lockout Section of Applications Information. 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. Pin in Typical Applications Circuits. ...

  • Page 34

    ... Constant Frequency PWM, Interface and Switcher Optimized for IEEE-Compliant PD System. 750mA MOSFET, Programmable Classification, Synchronous No-Opto Flyback Controller, 50kHz to 250kHz Flyback Controller, 50kHz to 250kHz www.linear.com ● Control 2 C Control 42692fb LT 0409 REV B • PRINTED IN USA  LINEAR TECHNOLOGY CORPORATION 2009 ...