Datasheet

ManualsBrandsNXP SEMICONDUCTORS ManualsPMICsPMIC - PoE controller SOIC 20 W Controller (PD) DC/DC

Table Of Contents

IEEE 802.3af PD With Current Mode Switching Regulator

Document Number: MC34670

Rev. 3.0, 12/2006

Freescale Semiconductor

Advance Information

* This document contains certain information on a new product.

Specifications and information herein are subject to change without notice.

IEEE 802.3af PD With Current

Mode Switching Regulator

The 34670 combines a Power Interface Port for IEEE 802.3af

Powered Devices (PD) and a high performance current mode

switching regulator. It allows a designer to build PDs with a minimum

of external components by means of integrating the required IEEE

802.3af functions and all functions necessary to build a high

efficiency DC/DC converter.

On the PD side the 34670 fully supports the IEEE802.3af standard

and provides complete signature and power classification functions.

It controls inrush current limiting and incorporates adjustable

undervoltage lockout. The switching regulator provides excellent line

and load regulation. It drives an external Power MOSFET with sense

resistor.

Features

• Integrated IEEE 802.3af Compliant Interface

• Signature Detection and Classification Functionality

• Integrated Isolation Switch

• Programmable Inrush Current Limiting Control

• Adjustable Undervoltage Lockout

• Input Voltage Range up to 80 V

• Current Mode Control

• Adjustable Oscillator

• Leading Edge Blanking

• Internal Slope Compensation Circuitry

• Input Overvoltage Protection

• 50% Duty Cycle Limitation

• Pb-Free Packaging Designated by Suffix Code EG

Figure 1. 34670 Simplified Application Diagram

POWER OVER ETHERNET

EG SUFFIX (PB-FREE)

98ASB42343B

20-PIN SOICW

34670

ORDERING INFORMATION

Device

Temperature

Range (T

)

Package

MCZ34670EG/R2 -40°C to 85°C 20 SOICW

PHY PHY

PSE HUB OR SWITCH

HOST

PSE POWER

CONTROLLER

48 V POWER

SUPPLY

-48V

GND

CAT 5

SWITCH

RJ-45

PROCESSOR

ETHERNET APPLIANCE (PD)

HOST

PD POWER

CONTROLLER

DC/DC

-48V

CONTROLLER

CABLE

ISOLATION SWITCH

34670

Summary of content (24 pages)

PAGE 1
Freescale Semiconductor Advance Information Document Number: MC34670 Rev. 3.0, 12/2006 IEEE 802.3af PD With Current Mode Switching Regulator 34670 The 34670 combines a Power Interface Port for IEEE 802.3af Powered Devices (PD) and a high performance current mode switching regulator. It allows a designer to build PDs with a minimum of external components by means of integrating the required IEEE 802.3af functions and all functions necessary to build a high efficiency DC/DC converter.
PAGE 2
INTERNAL BLOCK DIAGRAM INTERNAL BLOCK DIAGRAM FREQ HIGH VOLTAGE REGULATOR VPWR VDD 2.5V 8V INTERNAL SUPPLY 0.8R 5.7V R POR RCLA S R OSC GATE Q EN R 3.5V UV or UVLO UNDERVOLTAGE UV or UVLO LOCKOUT OVERVOLTAGE DETECTION 5µA + SS 0.3V CONTROL LOGIC S 4.5V Q R 5kΩ PWM COMPARATOR 0.6 - 2.6V 0.4V BLANK CS 1.4V 0.6V CURRENT LIMITATION ILIM UVLO + VIN 250mV RSENSE 3 + SLOPE COMP GATE DRIVE COMP FB TEMP SENSOR 1.2V REG DETECT VOUT RESET Figure 2.
PAGE 3
PIN CONNECTIONS PIN CONNECTIONS VPWR 1 20 VDD VPWR 2 19 GATE RCLA 3 18 CS UVLO 4 17 FB TEST1 5 16 COMP TEST2 6 15 SS FREQ 7 14 RESET ILIM 8 13 VOUT VIN 9 12 VOUT VIN 10 11 VOUT Figure 3. 34670 Pin Connections Table 1. 34670 Pin Definitions Pin Number Pin Name Formal Name Definition 1, 2 VPWR Positive Supply Voltage Input This is the most positive power supply input. The load connects between this pin and the VOUT pin.
PAGE 4
ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings All voltages are with respect to VIN unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device. Ratings Symbol Value Unit Power Supply Voltage VPWR -0.3 to 80 V Supply Current IPWR 18 mA VOUT Pins Voltage VOUT -0.3 to (VPWR + 0.3) V UVLO Voltage VUVLO -0.3 to 10 V RCLA Voltage VRCLA -0.3 to 5.0 V ILIM Voltage VILIM -0.
PAGE 5
ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings (continued) All voltages are with respect to VIN unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device.
PAGE 6
ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions 30 V ≤ VPWR ≤ 60 V, - 40°C ≤ TA ≤ 85°C, VIN = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions unless otherwise noted. Characteristic Symbol Min Typ Max Unit IOFFSET — — 10 µA RDIFF 600 — — kΩ 0 — 4.0 Class 1: RCLASS = 475 Ω 9.
PAGE 7
ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics(continued) Characteristics noted under conditions 30 V ≤ VPWR ≤ 60 V, - 40°C ≤ TA ≤ 85°C, VIN = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions unless otherwise noted. Characteristic Symbol Min Typ Max Unit VCOMP 1.3 — 4.0 V ICOMP(B) — — 1.8 mA VDDREG 8.0 9.0 10 V VDDReg +0.
PAGE 8
ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS Table 4. Dynamic Electrical Characteristics Characteristics noted under conditions 30 V ≤ VPWR ≤ 60 V, - 40°C ≤ TA ≤ 85°C, VIN = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions unless otherwise noted.
PAGE 9
ELECTRICAL CHARACTERISTICS TYPICAL SWITCHING WAVEFORMS TYPICAL SWITCHING WAVEFORMS w/o snubber w/ snubber w/ snubber w/o snubber Figure 4. Drain Voltage of Switching MOSFET Figure 6. Secondary Voltage before Diode Figure 5. Secondary and Output Voltage Figure 7.
PAGE 10
ELECTRICAL CHARACTERISTICS ELECTRICAL PERFORMANCE CURVES ELECTRICAL PERFORMANCE CURVES MC34670 Efficiency Plot: Vo = 5V, w/o bias winding, Coilcraft DA2142-AL 90.00 85.00 80.00 % 75.00 70.00 65.00 60.00 57V 55.00 48V 36V 50.00 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 I O [A] MC34670 Efficiency Plot: Vo = 5V, w/ bias winding, Coilcraft DA2362-AL 90.00 85.00 80.00 % 75.00 70.00 65.00 60.00 57V 48V 55.00 36V 50.00 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.
PAGE 11
FUNCTIONAL DESCRIPTION INTRODUCTION FUNCTIONAL DESCRIPTION INTRODUCTION The 34670 combines a Power Interface Port for IEEE 802.3af Powered Devices (PD) and a high performance current mode switching regulator. It allows a designer to build PDs with a minimum of external components by means of integrating the required IEEE 802.3af functions and all functions necessary to build a high efficiency DC/DC converter. Thus 34670 gives the system designer a device that drastically reduces cost and board space.
PAGE 12
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES POWER DEVICES (PD) INTERFACE The PD interface of the 34670 has been designed to comply with the requirements of the IEEE standard 802.3af. The device operates in three different modes, depending on the input voltage. I PD OPERATING MODES The IEEE 802.3af standard defines three operating modes in general. These modes are summarized in Table 5. Table 5.
PAGE 13
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES CLASSIFICATION CLASSIFICATION SIGNATURE LOAD CURRENT A PD may optionally be classified by the PSE. The intent of classification is to provide a method for more efficient power allocation through the PSE. The PD classification allows the PSE to identify four different (power) classes depending on the required power that the PD will draw during normal operation. The classes and the corresponding maximum power drawn by the PD is shown in Table 6.
PAGE 14
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES signature resistor, the total resistance of R1+R2 must equal 25 kΩ. R 1 = R SIG – R 2 V UVLO ( OFF ) = V UVLO ( ON ) ⋅ 0.85 +VPORT VPWR RCLA R1 UVLO R2 ILIM VIN -VPORT Figure 13. UVLO Adjustment by External Resistor Divider The typical turn-off voltage VUVLO(OFF) is 85% of the turn on voltage VUVLO(ON).
PAGE 15
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES converters running in continuos conduction mode (CCM). The value of the slope compensation depends on the switching frequency. See Table 10. T1 NP Table 10. Slope Compensation Values Switching Frequency [kHz] Slope Compensation [mV/µs] 100 10 250 25 400 50 NS RV ISOLATED OPTOCOUPLER FEEDBACK Isolated voltage feedback can be accomplished by using an optocoupler and a shunt regulator (see Figure 19).
PAGE 16
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES VDD This reduces power dissipation in the device and improves overall efficiency. 12 VREG(OFF) VGATE(R) 10 CURRENT-SENSE COMPARATOR 8 VGATE(F) When the overvoltage protection is triggered (VPWR > VOV(R)), the gate driver is immediately disabled. At the same time, the slow discharge of CSS is initiated. While the soft-start capacitor is discharging, the gate driver remains disabled. Once VSS = 0.
PAGE 17
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES voltage is out of regulation. In this case the RESET pin is pulled low. The RESET output can only be used in non-isolated applications. There is a 20 µs delay filter preventing erroneous RESET output pulses. During soft-start, RESET is held low. RESET is released when the PWM controller is in regulation. N-CHANNEL MOSFET GATE DRIVER GATE drives an N-channel MOSFET. GATE sources and sinks large transient currents up to 1.
PAGE 18
TYPICAL APPLICATIONS TYPICAL APPLICATIONS Please refer to application note AN3279 for further information of PD design and layout recommendations. T1 NAUX +VPORT VOUT = 5V@2A 3 NP 34670 RX NS VPWR 6 RESET 1 RCLA VDD TX 2 R1 CIN RCLASS UVLO R2 4 GATE 5 CDD 0.1 F RV CPORT CS ILIM VIN M1 RCS SS FREQ COMP FB VOUT -VPORT CSS 7 8 Figure 18.
PAGE 19
TYPICAL APPLICATIONS T1 +VPORT NR 3 NP 34670 RX NS VPWR 6 RESET 1 RCLA VDD TX 2 R1 CIN UVLO R2 4 M1 GATE RCLASS CDD RV CPORT CS ILIM RCS Rv1 5 VIN SS FREQ COMP FB VOUT Rv2 -VPORT CSS 7 8 Figure 20. Isolated Forward Converter T1 CAUX NAUX +VPORT VOUT = 5V@2A 3 NP 34670 RX NS VPWR 6 RESET 1 RCLA VDD TX 2 R1 CIN RCLASS UVLO R2 4 5 GATE CDD CPORT CS ILIM VIN M1 RCS SS FREQ COMP -VPORT CSS FB VOUT C2 R2 7 C1 8 Figure 21.
PAGE 20
TYPICAL APPLICATIONS +VPORT T1 3 NP 34670 RX VOUT = 5V@2A NS D1 CO VPWR 6 RESET 1 RCLA VDD TX 2 R3 CIN RCLASS UVLO R4 4 5 VIN CDD CPORT CS ILIM RCS SS FREQ COMP -VPORT CSS FB VOUT C2 R1 R2 7 8 M1 GATE Rb C1 Figure 22.
PAGE 21
REFERENCE DOCUMENTS REFERENCE DOCUMENTS Table 11. Reference Documents Title IEEE Std 802.3af™-2003 MC34670 Usage and Configuration LIterature Order Number Publication Date IEEE Std 802.
PAGE 22
PACKAGING PACKAGE DIMENSIONS PACKAGING PACKAGE DIMENSIONS For the most current package revision, visit www.freescale.com and perform a keyword search using the “98A” listed below.
PAGE 23
REVISION HISTORY REVISION HISTORY Revision Date Description of Changes 1.0 8/2006 • Initial release 2.0 9/2006 3.
PAGE 24
How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. Technical Information Center, EL516 2100 East Elliot Road Tempe, Arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.