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PDF MCZ34670 Data sheet ( Hoja de datos )
| Número de pieza | MCZ34670 | |
| Descripción | IEEE 802.3af PD | |
| Fabricantes | Motorola Semiconductor | |
| Logotipo |  |
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Freescale Semiconductor
Advance Information
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
Document Number: MC34670
Rev. 2.0, 9/2006
34670
POWER OVER ETHERNET
EG SUFFIX (PB-FREE)
98ASB42343B
20-PIN SOICW
ORDERING INFORMATION
Device
Temperature
Range (TA)
Package
MCZ34670EG/R2 -40°C to 85°C
20 SOICW
PSE HUB OR SWITCH
PHY
TX
RX
HOST
PROCESSOR
48 V POWER
SUPPLY
PSE POWER
CONTROLLER
SWITCH -48V
GND
RJ-45
CAT 5
CABLE
ETHERNET APPLIANCE (PD)
RX
PHY
TX
HOST
CONTROLLER
-48V
PD POWER
CONTROLLER
ISOLATION SWITCH
34670
DC/DC
Figure 1. 34670 Simplified Application Diagram
* This document contains certain information on a new product.
Specifications and information herein are subject to change without notice.
© Freescale Semiconductor, Inc., 2006. All rights reserved.
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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.
Ratings
Symbol
Value
Unit
THERMAL RATINGS
Operating Temperature
Ambient (4)
Junction (7), (8)
°C
TA -40 to 85
TJ 120
Storage Temperature
Power Dissipation (TA = 25 °C) (6)
TSTG
PD
-65 to 150
800
°C
mW
Thermal Resistance
Junction to Ambient
20LD SOIC W/B Package (8)
RθJA
RθJB
°C/W
103
47
Peak Package Reflow Temperature During Solder Mounting (5)
TSOLDER
300
°C
Thermal Shutdown Temperature
TSHUT
180
°C
Thermal Shutdown Hysteresis Temperature
THYST
30
°C
NotesNotes
4. The limiting factor is junction temperature; taking into account the power dissipation, thermal resistance, and heat sinking.
5. Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may
cause malfunction or permanent damage to the device.
6. Maximum power dissipation at indicated ambient temperature in free air with no heatsink used.
7. For TA = 85°C and PD = 700 mW and RθJB = 47°C/W.
8. Measured with 4 layers 2s2p JEDEC std. PCB.
Analog Integrated Circuit Device Data
Freescale Semiconductor
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34670
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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.
On the PD side the 34670 fully supports the IEEE802.3af
standard and provides complete signature detection and
power classification functions. It controls inrush current
limiting and incorporates an adjustable undervoltage lockout.
The 34670 includes thermal protection circuitry to protect the
device in case of high power dissipation.
The 34670 also offers an input overvoltage detection to
protect the external switching MOSFET by disabling the gate
driver in case of input line overvoltage.
The switching regulator provides excellent line and load
regulation. It drives an external power MOSFET with sense
resistor. The switching frequency is adjustable between
100 kHz and 400 kHz. The output voltage feedback
information can be accomplished by an optocoupler, if
isolation is required.
An internal logic control block manages the sequencing of
signature detection, classification and proper turn on and turn
off of the DC/DC converter.
FUNCTIONAL PIN DESCRIPTION
POSITIVE SUPPLY VOLTAGE INPUT (VPWR)
This is the most positive power supply input. The load
connects between this pin and the VOUT pin.
CLASSIFICATION RESISTOR (RCLA)
Connect a resistor between RCLA and VIN to select the
class of the PD.
UNDERVOLTAGE LOOKOUT (UVLO)
Used to adjust the undervoltage lookout threshold voltage,
connected to VIN to use the default threshold voltage.
TEST PINS (TEST1, TEST2)
Connect to VIN in application mode.
FREQUENCY ADJUSTMENT (FREQ)
Adjusts the internal oscillator frequency by connecting a
resistor between FREQ and VIN.
INRUSH CURRENT LIMIT (ILIM)
Used to adjust the inrush current limit of the isolation
switch, add a resistor between ILIM and VIN.
NEGATIVE SUPPLY VOLTAGE (VIN)
This is the most negative power supply input.
OUTPUT VOLTAGE (VOUT)
This pin is the drain of the internal Power MOSFET (high
current path and low current path).
RESET OUTPUT (RESET)
This is an active-low RESET output signal. This pin is
referenced to VOUT.
SOFT START INPUT (SS)
Connect an external capacitor to SS. The internal current
source charges the capacitor and generates a soft-start
ramp.
COMPENSATION PIN (COMP)
COMP is the output of the error amplifier and is available
for feedback compensation. COMP is pulled-up by an
internal 5.0 kΩ resistor to 5.0 V.
FEEDBACK INPUT (FB)
This is the inverting input of the error amplifier. In non-
isolated applications it’s connected to the secondary output
through a resistor divider.
CURRENT SENSE (CS)
The current sense pin CS senses a voltage that is
proportional to the current through the sense resistor.
GATE DRIVER OUTPUT (GATE)
GATE drives the gate of the external power MOSFET.
GATE sources and sinks up to 1.0 A.
VDD OUTPUT (VDD)
VDD mainly supplies the gate of the external power
MOSFET. Connect a capacitor from VDD to VOUT.
Analog Integrated Circuit Device Data
Freescale Semiconductor
DataSheet4 U .com
34670
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