ltc4269cdkd-2

Manufacturer Part Numberltc4269cdkd-2
DescriptionIeee 802.3at High Power Pd And Synchronous Forward Controller With Aux Support
ManufacturerLinear Technology Corporation
ltc4269cdkd-2 datasheet
 


1
Page 1
2
Page 2
3
Page 3
4
Page 4
5
Page 5
6
Page 6
7
Page 7
8
Page 8
9
Page 9
10
Page 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Page 1/32

Download datasheet (281Kb)Embed
Next
FEATURES
n
25.5W IEEE 802.3at Compliant (Type-2) PD
+
n
PoE
2-Event Classifi cation
n
IEEE 802.3at High Power Available Indicator
n
Integrated State-of-the-Art Synchronous Forward
Controller
– Isolated Power Supply Effi ciency >94%
n
Flexible Auxiliary Power Interface
n
Superior EMI Performance
n
Robust 100V 0.7Ω (Typ) Integrated Hot Swap™
MOSFET
n
Integrated Signature Resistor, Programmable Class
Current, UVLO, OVLO and Thermal Protection
n
Short-Circuit Protection with Auto-Restart
n
Programmable Switching Frequency from
100kHz to 500kHz
Thermally Enhanced 7mm × 4mm DFN Package
n
APPLICATIONS
n
IP Phones with Large Color Screens
n
Dual Radio 802.11n Access Points
n
PTZ Security Cameras
TYPICAL APPLICATION
PoE-Based Self-Driven Synchronous Forward Power Supply
10μH
+
10μF
2.2μF
~
+
54V FROM
DATA PAIR
~
~
+
54V FROM
SPARE PAIR
~
0.1μF
30.9Ω
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
classifi cation signaling, fl exible auxiliary power op-
tions, and a power supply controller suitable for syn-
chronously rectifi ed 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 classifi cation, 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 rectifi cation, resulting
in an extremely high effi ciency, green product. Soft-start
for controlled output voltage start-up and fault recovery is
included. Programmable frequency over 100kHz to 500kHz
allows fl exibility in effi ciency vs size and low EMI.
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.
1mH
33k
237k
0.1μF
V
CC
+
10.0k
10μF
10k
133Ω
SD_V
V
S
OUT
SEC
IN
OUT
V
OC
PORTP
I
SENSE
LTC4269-2
R
COMP
CLASS
SHDN
FB
V
V
REF
PORTN
T2P V
PGND
GND BLANK DELAY
R
SS_MAXDC
NEG
OSC
82k
332k
158k
158k
TO
MICRO-
CONTROLLER
LTC4269-2
6.8μH
+
5.1Ω
220μF
4.7nF
4.7nF
V
CC
2k
11.3k
1.5k
50mΩ
10nF
33k
22k
1.2k
22.1k
TLV431
0.1μF
3.65k
0.22μF
42692 TA01
5V
5A
42692f
1

ltc4269cdkd-2 Summary of contents

  • Page 1

    ... EMI. 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. ...

  • Page 2

    ... LTC4269IDKD-2#TRPBF LEAD BASED FINISH TAPE AND REEL LTC4269CDKD-2 LTC4269CDKD-2#TR LTC4269IDKD-2 LTC4269IDKD-2#TR Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifi ...

  • Page 3

    ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER Interface Controller (Note 5) Operating Input Voltage Signature Range Classifi cation Range On Voltage Undervoltage Lockout Overvoltage Lockout ON/UVLO Hysteresis Window Signature/Class Hysteresis Window Reset Threshold Supply Current Supply ...

  • Page 4

    LTC4269-2 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER SD_V Current SEC(ON) SD_V Current 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) ...

  • Page 5

    ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at 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 ...

  • 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 5.0 50 –50 – 100 TEMPERATURE (°C) 42692 G19 I Maximum Threshold vs SENSE Temperature 240 COMP = 2.5V ...

  • Page 9

    TYPICAL PERFORMANCE CHARACTERISTICS t : SOUT Rise to OUT Rise vs DELAY Temperature 200 150 R = 120k DELAY 100 40k DELAY 0 – –25 100 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

    PIN 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 EXPOSED PAD START- INPUT CURRENT (ISTART OFF IN + – I HYST 10μA SD_V SEC 0μA ...

  • Page 13

    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 ...

  • 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

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

  • 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

    APPLICATIONS INFORMATION 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 there are several possible scenarios where a PD may encounter excessive heating. During classifi cation, excessive heating may occur if the PSE exceeds the 75ms probing time limit. At turn-on, when the load capacitor begins to charge, ...

  • Page 19

    APPLICATIONS INFORMATION a temperature and voltage dependency that can reduce the perceived signature resistance. In addition, the IEEE 802.3af/at specifi cation mandates the leakage back-feeding through the unused bridge cannot generate more than 2.8V across a 100k resistor when a ...

  • Page 20

    LTC4269-2 APPLICATIONS INFORMATION + V V PORTP LTC4269 PSE T2P V –54V PORTN OPTION 1: SERIES CONFIGURATION FOR ACTIVE LOW/LOW IMPEDANCE OUTPUT + V V PORTP R LTC4269-2 TO T2P PSE V V –54V PORTN NEG OPTION 2: ...

  • Page 21

    APPLICATIONS INFORMATION Part Start-Up In normal operation, the SD_V pin must exceed 1.32V SEC and the V pin must exceed 14.25V to allow the part IN to turn on. This combination of pin voltages allows the 2.5V V pin to ...

  • Page 22

    LTC4269-2 APPLICATIONS INFORMATION maximum duty cycle clamp, the SS_MAXDC pin voltage is programmed by a resistor divider from the 2.5V V pin to GND. An increase of programmed voltage on SS_MAXDC pin provides an increase of switch maximum duty cycle ...

  • Page 23

    APPLICATIONS INFORMATION loss of slope compensation during synchronization, the free running oscillator frequency should be programmed OSC to 80% of the external clock frequency (f resistor chosen for nonsynchronized operation should be increased by 1.25x (= f /f ...

  • Page 24

    LTC4269-2 APPLICATIONS INFORMATION 500 450 400 350 300 250 200 150 100 50 100 150 200 250 300 R (kΩ) OSC Figure 11. Oscillator Frequency, f Stray capacitance and potential noise pickup on the R pin should be minimized by ...

  • Page 25

    APPLICATIONS INFORMATION compensation requirements. Current mode switching regulators which operate with duty cycles above 50% and have continuous inductor current must add slope compensation to their current sensing loop to prevent subharmonic oscillations. (For more information on slope compensation, see ...

  • Page 26

    LTC4269-2 APPLICATIONS INFORMATION To program the volt-second clamp, the following steps should be taken: (1) The maximum operational duty cycle of the converter should be calculated for the given application. (2) An initial value for the maximum duty cycle clamp ...

  • Page 27

    APPLICATIONS INFORMATION t : 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 Example For an overcurrent fault (OC > 100mV 35.7k 100k 0.1μF and assume 0.45V, SS(MIN) ≅ 8e – (2.5 – 0.45)[(1/2 • 100k) ...

  • Page 29

    APPLICATIONS INFORMATION From Step 1 and Step 2 – (1.5 – 0.73 7.7e CHARGE The total time of no switching for the converter due to a soft-start event – 1.85e DISCHARGE ...

  • Page 30

    LTC4269-2 TYPICAL APPLICATION 30 (%) EFFICIENCY 42692f ...

  • Page 31

    ... 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 × ...

  • Page 32

    ... High Power PD Interface with Integrated Switching Regulator LTC4269-1 IEEE 802.3at PD Interface Integrated Switching Regulator 2-Event Classifi cation, Programmable Classifi cation, Synchronous No-Opto ThinSOT is a trademark of Linear Technology Corporation. Linear Technology Corporation 32 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● ...