Rainbow Electronics MAX5945 User Manual

General Description

The MAX5945 quad network power controller is designed for use in IEEE 802.3af-compliant power-sourcing equipment (PSE). The device provides power devices (PD) discovery, classification, current-limit, and both DC and AC load disconnect detections. The MAX5945 can be used in either endpoint PSE (LAN switches/routers) or midspan PSE (power injector) applications. The MAX5945 is pin and function compatible with LTC4259A.

The MAX5945 can operate autonomously or be controlled by software through an I2C*-compatible interface. Separate input and output data lines (SDAIN and SDAOUT) allow usage with optocouplers. The MAX5945 is a slave device. Its four address inputs allow 16 unique MAX5945 addresses. A separate INT output and four independent shutdown inputs (SHD_) allow fast response from a fault to port shutdown. A RESET input allows hardware reset of the device. A special watchdog feature allows the hardware to gracefully take over control if the software crashes. A cadence timing feature allows the MAX5945 to be used in midspan systems.

The MAX5945 is fully software configurable and programmable. A class-overcurrent detection function enables system power management to detect if a PD draws more current than the allowable amount for its class. Other features are input under/overvoltage lockout, overtemperature protection, output-voltage slew-rate limit during startup, power-good, and fault status. The MAX5945’s programmability includes gate-charging current, currentlimit threshold, startup timeout, overcurrent timeout, autorestart duty cycle, PD disconnect AC detection threshold, and PD disconnect detection timeout.

The MAX5945 is available in a 36-pin SSOP package and is rated for both extended (-40°C to +85°C) and commercial (0°C to +70°C) temperature ranges.

Applications

Power-Sourcing Equipment (PSE)

Power-Over-LAN/Power-Over-Ethernet

Switches/Routers

Midspan Power Injectors

Features

♦ IEEE 802.3af Compliant

♦ Pin and Function Compatible with LTC4259A

♦ Controls Four Independent, -48V-Powered

Ethernet Ports in Either Endpoint or Midspan PSE Applications

♦ Wide Digital Power Input, V

DIG

, Common-Mode

Range: VEEto (AGND + 7.7V)

♦ PD Violation of Class Current Protection

♦ PD Detection and Classification

♦ Provides Both DC and AC Load Removal

Detections

♦ I2C-Compatible, 3-Wire Serial Interface

♦ Fully Programmable and Configurable Operation

Through I

C Interface

♦ Current Foldback and Duty-Cycle-

Controlled/Programmable Current Limit

♦ Short-Circuit Protection with Fast Gate Pulldown

♦ Direct Fast Shutdown Control Capability

♦ Programmable Direct Interrupt Output

♦ Watchdog Mode Enable Hardware Graceful

Takeover

MAX5945

Quad Network Power Controller

for Power-Over-LAN

________________________________________________________________ Maxim Integrated Products 1

Pin Configuration

19-3428; Rev 1; 9/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

Ordering Information

*Purchase of I2C components from Maxim Integrated Products, Inc. or one of its sublicensed Associated Companies, conveys a license under the Philips I

C Patent

Rights to use these components in an I

C system, provided

that the system conforms to the I

C Standard Specification as

defined by Philips.

**Future product—contact factory for availability.

Typical Operating Circuits appear at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX5945CAX** 0°C to +70°C 36 SSOP

MAX5945EAX -40°C to +85°C 36 SSOP

TOP VIEW

RESET

MIDSPAN

SDAOUT

SDAIN

DET1

DET2

DET3

DET4

DGND

SHD1

SHD2

INT

SCL

OSC_IN

AUTO

OUT1

GATE1

MAX5945

SSOP

SENSE1

OUT2

GATE2

SENSE2

OUT3

GATE3

SENSE3

OUT4

GATE4

SENSE4

AGNDV

SHD4

SHD3

MAX5945

Quad Network Power Controller for Power-Over-LAN

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

(Voltages referenced to VEE, unless otherwise noted.) AGND, DGND, DET_, V

, RESET, A3, A2, A1, A0, SHD_,

OSC_IN, SCL, SDAIN, OUT_ and AUTO............-0.3V to +80V

GATE_ (internally clamped, Note 1)....................-0.3V to +11.4V

SENSE_ ..................................................................-0.3V to +24V

, RESET, A3, A2, A1, A0, SHD_, OSC_IN, SCL, SDAIN and

AUTO to DGND ....................................................-0.3V to +7V

INT and SDAOUT to DGND....................................-0.3V to +12V

Maximum Current into INT, SDAOUT, DET_ .......................80mA

Maximum Power Dissipation

36-Pin SSOP (derate 11.4mW/°C above +70°C) .........941mW

Operating Temperature Ranges:

MAX5945EAX ..................................................-40°C to +85°C

MAX5945CAX .....................................................0°C to +70°C

Storage Temperature Range .............................-65°C to +150°C

Junction Temperature......................................................+150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(AGND = +32V to +60V, VEE= 0V, VDDto DGND = +3.3V, all voltages are referenced to VEE, unless otherwise noted. Typical values are at AGND = +48V, DGND = +48V, V

= (DGND + 3.3V), TA= +25°C. Currents are positive when entering the pin and

negative otherwise.)

Note 1: GATE_ is internally clamped to 11.4V above VEE. Driving GATE_ higher than 11.4V above VEEmay damage the device.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

POWER SUPPLIES

AGNDVAGND

Operating Voltage Range

Supply Currents

DGND

DIG

GATE DRIVER AND CLAMPING

GATE_ Pullup Current I

Weak GATE_ Pulldown Current I

Maximum Pulldown Current I

External Gate Drive V

PDW

PDS

CURRENT LIMIT

Current-Limit Clamp Voltage V

Overcurrent Threshold After Startup

Foldback Initial OUT_ Voltage V

Foldback Final OUT_ Voltage V

SU_LIM

FLT_LIM

FLBK_ST

FLBK_END

- V

VDD to V

DGND, VDGND

OUT_ = VEE, SENSE_ = VEE, DET_ = AGND, all logic inputs open, SCL = SDAIN = V INT and SDAOUT open; measured at AGND in power mode after GATE_ pullup

All logic inputs high, measured at V

Power mode, gate drive on, V SHD_ = DGND, V

= 1V, V

SENSE

- VEE , power mode, gate drive on 9 10 11 V

GATE

Maximum V V

OUT_

Overcurrent V

SENSE_

= VEE (Note 3)

SENSE_

threshold allowed for t ≤ t V

OUT_

after startup;

FAULT

= V

- VEE, above which the current-limit trip

voltage starts folding back

- VEE, above which the current-limit trip

OUT_

voltage reaches V

32 60

060

= V

AGND

= V

GATE

= V

GATE_

= V

GATE_

allowed during current limit,

+ 5V 30 40 50 µA

+ 2V 100 mA

Default, class 0, class 3, class 4

(Note 2) -40 -50 -60 µA

1.71 5.50

3.0 5.5

4.2 6.8

2.7 5.6

202 212 220 mV

178.5 196

Class 1 49 61

Class 2 90 104

30 V

TH_FB

50 V

MAX5945

Quad Network Power Controller

for Power-Over-LAN

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(AGND = +32V to +60V, VEE= 0V, VDDto DGND = +3.3V, all voltages are referenced to VEE, unless otherwise noted. Typical values are at AGND = +48V, DGND = +48V, V

= (DGND + 3.3V), TA= +25°C. Currents are positive when entering the pin and

negative otherwise.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Minimum Foldback CurrentLimit Threshold

TH_FBVOUT_

SENSE_ Input Bias Current V

SUPPLY MONITORS

VEE Undervoltage Lockout V

VEE Undervoltage-Lockout Hysteresis

VEE Overvoltage V

VEE Overvoltage Hysteresis V

VEE Undervoltage V

VDD Overvoltage V

VDD Undervoltage V

VDD Undervoltage Lockout V

VDD Undervoltage-Lockout Hysteresis

Thermal-Shutdown Threshold T

Thermal-Shutdown Hysteresis T

EEUVLOVAGND

EEUVLOH

EE_OV

OVH

EE_UV

DD_OV(VDD

DD_UV(VDD

DDUVLO

DDHYS

SHD

SHDH

OUTPUT MONITOR

OUT_ Input Current I

Idle Pullup Current at OUT_ I

PGOOD High Threshold PG

PGOOD Hysteresis PG

PGOOD Low-to-High Glitch Filter

BOUT

DIS

HYS

PGOOD

LOAD DISCONNECT

DC Load Disconnect Threshold

DCTH

= V

SENSE_

AGND

= V

- VEE, (V

- VEE) increasing 27 28.5 30 V

AGND

64 mV

-2 µA

AGND

- VEE) > V

EE_OV

, V

increasing 61 62.5 64 V

AGND

- VEE) < V

AGND

- V

DGND)

DGND

> V

) < V

Device operates when (VDD - V V

DDUVLO

, VDD increasing

EE_UV

DD_OV

DD_UV

, V

decreasing 39 40 41 V

AGND

, VDD increasing 3.57 3.71 3.90 V

, VDD decreasing 2.55 2.82 2.97 V

) >

DGND

1.7 V

120 mV

Ports shut down and device resets if its junction temperature exceeds this limit, temperature

+150 °C

increasing

20 °C

OUT

= V

, all modes 2 µA

AGND

OUT_ discharge current, detection and classification off, port shutdown, V

= V

OUT_

- VEE, OUT_ decreasing 1.8 2.0 2.2 V

OUT_

AGND

- 2.8V

200 260 µA

220 mV

Minimum time PGOOD has to be high to set bit in register 10h

Minimum V disconnect active), V

allowed before disconnect (DC

SENSE

OUT_

= V

24ms

345mV

MAX5945

Quad Network Power Controller for Power-Over-LAN

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(AGND = +32V to +60V, VEE= 0V, VDDto DGND = +3.3V, all voltages are referenced to VEE, unless otherwise noted. Typical values are at AGND = +48V, DGND = +48V, V

= (DGND + 3.3V), TA= +25°C. Currents are positive when entering the pin and

negative otherwise.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

AC Load Disconnect Threshold (Note 4)

Oscillator Buffer Gain A

OSC_IN Fail Threshold (Note 5)

OSC_IN Input Resistance Z

OSC_IN Input Capacitance C

Load Disconnect Timer t

ACTH

OSC

OS C _F AI L

OSC

OSC_IN

DISC

DETECTION

Detection Probe Voltage (First Phase)

Detection Probe Voltage (Second Phase)

Current-Limit Protection I

Short-Circuit Threshold V

Open-Circuit Threshold I

Resistor Detection Window R

Resistor Rejection Window R

DPH1VAGND

DPH2

DLIM

DCP

D_OPEN

DOK

DBAD

CLASSIFICATION

Classification Probe Voltage V

Current-Limit Protection I

Classification Current Thresholds

ClLIM

DIGITAL INPUTS/OUTPUTS (REFERRED to DGND)

Digital Input Low V

Digital Input High V

Current into DET_, ACD_EN_ bit = high, OSC_IN = 2.2V

/ V

DET_

= 400nF

DET

Port will not power on if V

, ACD_EN_ bit = high,

OSC_IN

< V

OSC_FAIL

and

ACD_EN_ bit = high

OSC_IN input impedance when all the ACD_EN_ are active

300 325 350 µA

2.92 2.98 3.04 V/V

1.8 1.9 2.1 V

100 kΩ

5pF

Time from V

to gate shutdown (Note 6)

< I

ACTH

- V

AGND

phase

= V

DET_

current through DET_

If V

A GN D

- V

p hase a shor t ci r cui t to AG N D i s d etected

First point measurement current threshold for open condition

< V

SENSE

during the first detection phase 3.8 4 4.2 V

DET_

during the second detection

DET_

, during detection, measure

AGND

< V

OU T

or current into DET_

DCTH

after the fi r st d etecti on

D C P

300 400 ms

9.0 9.3 9.6 V

1.5 1.75 2.0 mA

1.62 V

12.5 µA

(Note 7) 18.6 26.5 kΩ

Detection rejects lower values 16

Detection rejects higher values 30

- V

AGND

= V

DET_

measure current through DET_

during classification 16 20 V

DET_

, during classification,

AGND

50 75 mA

Class 0, class 1 5.5 6.5 7.5

Classification current thresholds between classes

Class 1, class 2 13.5 14.5 15.5

Class 2, class 3 21.5 23 24.5

Class 3, class 4 31 33 35

>Class 4 45 48 51

0.9 V

2.4 V

kΩ

MAX5945

Quad Network Power Controller

for Power-Over-LAN

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(AGND = +32V to +60V, VEE= 0V, VDDto DGND = +3.3V, all voltages are referenced to VEE, unless otherwise noted. Typical values are at AGND = +48V, DGND = +48V, V

= (DGND + 3.3V), TA= +25°C. Currents are positive when entering the pin and

negative otherwise.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Internal Input Pullup/Pulldown Resistor

Open-Drain Output Low Voltage

Open-Drain Leakage I

TIMING

Startup Time t

Fault Time t

Port Turn-Off Time t

Detection Time t

Midspan Mode Detection Delay

Classification Time t

Restart Timer t

Watchdog Clock Period t

TIMING CHARACTERISTICS for 2-WIRE FAST MODE (Figures 5 and 6)

Serial Clock Frequency f

Bus Free Time Between a STOP and a START Condition

Hold Time for Start Condition t

Low Period of the SCL Clock t

High Period of the SCL Clock t

Turn-On Delay t

EEUVLO

DIN

START

FAULT

OFF

DET

DMID

CLASS

DLY

RESTART

SCL

BUF

HD, STA

LOW

HIGH

Pullup (pulldown) resistor to VDD (DGND) to set default level

= 15mA 0.4 V

SINK

Open-drain high impedance, VO = 3.3V 2 µA

Time during which a current limit set by V is allowed, starts when the GATE_ is turned on (Note 8)

Maximum allowed time for an overcurrent condition set by V

Minimum delay between any port turning off, does not apply in the case of a reset

Maximum time allowed before detection is completed

Time allowed for classification 40 ms

Time V thresholds before the device operates

Ti m e a p or t has to w ai t b efor e tur ni ng on after an over cur r ent faul t, RS TR_E N b i t = hi g h

Rate of decrement of the watchdog timer 164 ms

(Note 9) 400 kHz

(Note 9) 1.2 µs

(Note 9) 0.6 µs

(Note 9) 1.2 µs

(Note 9) 0.6 µs

must be above the V

AGND

after startup (Note 8)

FLT_LIM

RSTR bits = 00

RSTR bits = 01

RSTR bits = 10

RSTR bits = 11 0

SU_LIM

EEUVLO

25 50 75 kΩ

50 60 70 ms

0.5 0.75 1.0 ms

320 ms

2.0 2.4 s

24ms

16 x

FAULT

32 x

FAULT

64 x

FAULT

MAX5945

Quad Network Power Controller for Power-Over-LAN

6 _______________________________________________________________________________________

Note 2: Default values. The charge/discharge currents are programmable through the serial interface (see the Register Map and

Description section).

Note 3: Default values. The current-limit thresholds are programmed through the I

C-compatible serial interface (see the Register

Map and Description section).

Note 4: This is the default value. Threshold can be programmed through serial interface R23h[2:0]. Note 5: AC disconnect works only if V

- V

DGND

≥ 3V.

Note 6: t

DISC

can also be programmed through the serial interface (R29h) (see the Register Map and Description section).

Note 7: R

= (V

OUT_2

- V

OUT_1

) / (I

DET_2

- I

DET_1

). V

OUT_1

, V

OUT_2

, I

DET_2

and I

DET_1

represent the voltage at OUT_ and the current

at DET_ during phase 1 and 2 of the detection.

Note 8: Default values. The startup and fault times can also be programmed through the I

C serial interface (see the Register Map

and Description section).

Note 9: Guaranteed by design. Not subject to production testing.

ANALOG SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX5945 toc01

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

5752474237

3.6

3.7

3.8

3.9

4.0

4.1

4.2

4.3

4.4

4.5

3.5 32 62

MEASURED AT AGND

ANALOG SUPPLY CURRENT

vs. TEMPERATURE

MAX5945 toc02

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

5.0

3.0

-40 85

DIGITAL SUPPLY CURRENT

vs. TEMPERATURE

MAX5945 toc03

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

-40 85

Typical Operating Characteristics

(VEE= -48V, VDD= +3.3V, AUTO = AGND = DGND = 0V, RESET = SHD_ = unconnected, R

SENSE

= 0.5Ω, all registers = default setting,

= +25°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS (continued)

(AGND = +32V to +60V, VEE= 0V, VDDto DGND = +3.3V, all voltages are referenced to VEE, unless otherwise noted. Typical values are at AGND = +48V, DGND = +48V, V

= (DGND + 3.3V), TA= +25°C. Currents are positive when entering the pin and

negative otherwise.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Setup Time for a Repeated START Condition (Sr)

Data Hold Time t

Data Setup Time t

Rise Time of Both SDA and SCL Signals, Receiving

Fall Time of SDA Transmitting t

Setup Time for STOP Condition t

C ap aci ti ve Load for E ach Bus Li ne

Pulse Width of Spike Suppressed

SU, STA

HD, DAT

SU, DAT

SU, STO

(Note 9) 0.6 µs

(Note 9) 0 150 ns

(Note 9) 100 ns

(Note 9) 20 + 0.1C

300 ns

(Note 9) 0.6 µs

(Note 9) 400 pF

(Note 9) 50 ns

MAX5945

Quad Network Power Controller

for Power-Over-LAN

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(VEE= -48V, VDD= +3.3V, AUTO = AGND = DGND = 0V, RESET = SHD_ = unconnected, R

SENSE

= 0.5Ω, all registers = default setting,

= +25°C, unless otherwise noted.)

DIGITAL SUPPLY CURRENT

vs. INPUT VOLTAGE

MEASURED AT V

SUPPLY CURRENT (mA)

1.8 5.0

INPUT VOLTAGE (V)

GATE OVERDRIVE

vs. TEMPERATURE

10.5

10.4

10.3

10.2

10.1

10.0

9.9

GATE OVERDRIVE (V)

9.8

9.7

9.6

9.5

-40 85 TEMPERATURE (°C)

30.0

29.5

MAX5945 toc04

29.0

28.5

28.0

UNDERVOLTAGE LOCKOUT (V)

27.5

4.64.23.83.43.02.62.2

603510-15

27.0

MAX5945 toc07

SENSE TRIP VOLTAGE (mV)

VEE UNDERVOLTAGE LOCKOUT

vs. TEMPERATURE

-40 85 TEMPERATURE (°C)

SENSE TRIP VOLTAGE

vs. TEMPERATURE

200

195

190

185

180

175

170

-40 85 TEMPERATURE (°C)

MAX5945 toc05

603510-15

MAX5945 toc08

603510-15

GATE OVERDRIVE

vs. INPUT VOLTAGE

9.98

9.96

9.94

9.92

9.90

9.88

9.86

GATE OVERDRIVE (V)

9.84

9.82

9.80

9.78 32 62

INPUT VOLTAGE (V)

SENSE TRIP VOLTAGE

vs. INPUT VOLTAGE

190

188

186

184

SENSE TRIP VOLTAGE (mV)

182

180

32 62

INPUT VOLTAGE (V)

MAX5945 toc06

5752474237

MAX5945 toc09

5752474237

FOLDBACK CURRENT-LIMIT

THRESHOLD vs. OUTPUT VOLTAGE

300

250

200

(mV)

150

- V

SENSE

100

050

- VEE (V)

OUT

MAX5945 toc10

DETECTION THRESHOLD (mV)

40302010

ZERO-CURRENT DETECTION

THRESHOLD vs. TEMPERATURE

-40 85 TEMPERATURE (°C)

603510-15

MAX5945 toc11

MAX5945

Quad Network Power Controller for Power-Over-LAN

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VEE= -48V, VDD= +3.3V, AUTO = AGND = DGND = 0V, RESET = SHD_ = unconnected, R

SENSE

= 0.5Ω, all registers = default setting,

= +25°C, unless otherwise noted.)

OVERCURRENT TIMEOUT

= 240Ω TO 57Ω)

LOAD

20ms/div

SHORT-CIRCUIT RESPONSE TIME

MAX5945 toc12

MAX5945 toc14

(AGND - OUT) 20V/div

OUT

200mA/div

GATE 10V/div

INT 2V/div

(AGND - OUT) 20V/div

OUT

250mA/div 0A

OVERCURRENT RESPONSE WAVEFORM

= 240Ω TO 57Ω)

LOAD

OUT

200mA/div

400µs/div

SHORT-CIRCUIT RESPONSE TIME

MAX5945 toc13

MAX5945 toc15

(AGND - OUT) 20V/div

GATE 10V/div V

INT 2V/div

(AGND - OUT) 20V/div

OUT

5A/div

GATE 10V/div V

20ms/div

RESET TO OUTPUT TURN-OFF DELAY

100µs/div

MAX5945 toc16

RESET

OUT

200mA/div 0A

(AGND - OUT) 20V/div

GATE 10V/div V

ZERO-CURRENT DETECTION WAVEFORM

4µs/div

MAX5945 toc17

100ms/div

GATE 10V/div V

(AGND - OUT) 20V/div

OUT

200mA/div

GATE 10V/div

INT 5V/div

MAX5945

Quad Network Power Controller

for Power-Over-LAN

_______________________________________________________________________________________ 9

Typical Operating Characteristics (continued)

(VEE= -48V, VDD= +3.3V, AUTO = AGND = DGND = 0V, RESET = SHD_ = unconnected, R

SENSE

= 0.5Ω, all registers = default setting,

= +25°C, unless otherwise noted.)

OVERCURRENT RESTART DELAY

400ms/div

MAX5945 toc18

DETECTION WITH INVALID PD

(25kΩ AND 10µF)

MAX5945 toc20

(AGND - OUT) 20V/div

OUT

200mA/div

GATE 10V/div V

(AGND - OUT) 2V/div 0V

OUT

1mA/div

STARTUP WITH VALID PD

(25kΩ AND 0.1µF)

100ms/div

DETECTION WITH INVALID PD (15kΩ)

MAX5945 toc19

MAX5945 toc21

(AGND - OUT) 20V/div

OUT

100mA/div

GATE_

(AGND - OUT) 5V/div 0V

OUT

1mA/div 0A

40ms/div

100ms/div

STARTUP IN MIDSPAN MODE

DETECTION WITH INVALID PD (33kΩ)

100ms/div

MAX5945 toc22

(AGND - OUT) 5V/div

OUT

1mA/div 0A

WITH VALID PD (25kΩ AND 0.1µF)

100ms/div

MAX5945 toc23

(AGND - OUT) 20V/div

OUT

100mA/div

GATE_ 10V/div V

MAX5945

Quad Network Power Controller for Power-Over-LAN

10 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VEE= -48V, VDD= +3.3V, AUTO = AGND = DGND = 0V, RESET = SHD_ = unconnected, R

SENSE

= 0.5Ω, all registers = default setting,

= +25°C, unless otherwise noted.)

DETECTION WITH MIDSPAN MODE

WITH INVALID PD (15kΩ)

400ms/div

DETECTION WITH OUTPUT SHORTED

40ms/div

MAX5945 toc24

MAX5945 toc26

(AGND - OUT) 5V/div

OUT

1mA/div 0A

GATE_ 10V/div

(AGND - OUT) 5V/div

OUT

1mA/div

GATE_ 10V/div V

DETECTION WITH MIDSPAN MODE

WITH INVALID PD (33kΩ)

400ms/div

MAX5945 toc25

DETECTION WITH INVALID PD (OPEN CIRCUIT,

USING TYPICAL OPERATING CIRCUIT 1)

100ms/div

MAX5945 toc27

(AGND - OUT) 5V/div

I 1mA/div 0A

GATE_ 10V/div V

(AGND - OUT) 5V/div

OUT

1mA/div 0A

GATE_ 10V/div V

OUT

DETECTION WITH INVALID PD (OPEN CIRCUIT,

USING TYPICAL OPERATING CIRCUIT 2)

100ms/div

MAX5945 toc28

(AGND - OUT) 5V/div

OUT

2mA/div

GATE_ 10V/div

STARTUP WITH DIFFERENT PD CLASSES

40ms/div

MAX5945 toc29

CLASS4

CLASS3

CLASS2

CLASS1 CLASS0

(AGND - OUT) 5V/div

OUT

10mA/div

MAX5945

Quad Network Power Controller

for Power-Over-LAN

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Pin Description

PIN NAME FUNCTION

Hardware Reset. Pull RESET low for at least 300µs to reset the device. All internal registers reset to

1 RESET

2 MIDSPAN

3 INT

4 SCL Serial Interface Clock Line

5 SDAOUT

6 SDAIN

7–10 A3, A2, A1, A0

11–14

15 DGND Connect to Digital Ground

16 V

17–20

21 AGND Analog Ground. Connect to the high-side analog supply.

22, 25,

29, 32

23, 26,

30, 33

24, 27,

31, 34

28 V

35 AUTO

36 OSC_IN

DET1, DET2,

DET3, DET4

SHD1, SHD2,

SHD3, SHD4

SENSE4, SENSE3,

SENSE2, SENSE1

GATE4, GATE3,

GATE2, GATE1

OUT4, OUT3,

OUT2, OUT1

their default value. The address (A0–A3), and AUTO and MIDSPAN input logic levels latch on during low-to-high transition of RESET. Internally pulled up to V

MIDSPAN Mode Input. An internal 50kΩ pulldown resistor to DGND sets the default mode to endpoint PSE operation (power-over-signal pairs). Pull MIDSPAN TO V MIDSPAN value latches after the IC is powered up or reset (see the PD Detection section).

Open-Drain Interrupt Output. INT goes low whenever a fault condition exists. Reset the fault condition using software or by pulling RESET low (see the Interrupt section of the Detailed Description for more information about interrupt management).

Serial Output Data Line. Connect the data line optocoupler input to SDAOUT (see the Typical Application Circuit). Connect SDAOUT to SDAIN if using a 2-wire I

Serial Interface Input Data Line. Connect the data line optocoupler output SDAIN (see the Typical Application Circuit). Connect SDAIN to SDAOUT if using a 2-wire wire I

Address Bits. A3, A2, A1, and A0 form the lower part of the device’s address. Address inputs default high with an internal 50kΩ pullup resistor to V up and exceeds its UVLO threshold or after a reset. The 3 MSB bits of the address are set to 010.

Detection and Classification Voltage Outputs. Use DET1 to set the detection and classification probe voltages on port 1. Use DET1 for the AC voltage sensing of port 1 when using the AC disconnect scheme (see the Typical Application Circuit).

Positive Digital Supply. Connect to digital supply (referenced to DGND). Port Shutdown Inputs. Pull SHD_ low to turn off the external FET on port_. Internally pulled up to V

with a 50kΩ resistor.

MOSFET Source Current-Sense Negative Inputs. Connect to the source of the power MOSFET and connect a current-sense resistor between SENSE_ and V

Port_ MOSFET Gate Drivers. Connect GATE_ to the gate of the external FET (see the Typical Application Circuit).

MOSFET Drain-Output Voltage Senses. Connect OUT_ to the power MOSFET drain through a resistor (100Ω to 100kΩ). The low leakage at OUT_ limits the drop across the resistor to less than 100mV (see the Typical Application Circuit).

Low-Side Analog Supply Input. Connect the low-side analog supply to VEE (-48V). Bypass with a 1µF capacitor between AGND and V

AUTO or SHUTDOWN Mode Input. Force high to enter AUTO mode after a reset or power-up. Drive low to put the MAX5945 into SHUTDOWN mode. In SHUTDOWN mode, software controls the operational modes of the MAX5945. A 50kΩ internal pulldown resistor defaults AUTO low. AUTO latches when V Software commands can take the MAX5945 out of AUTO while AUTO is high.

Oscillator Input. AC-disconnect detection function uses OSC_IN. Connect a 100Hz ±10%, 2V ±5%, +1.2V offset sine wave to OSC_IN. If the oscillator positive peak falls below the OSC_FAIL threshold of 2V, the ports that have the AC function enabled shut down and are not allowed to power up. When not using the AC-disconnect detection function, leave OSC_IN unconnected.

or VEE ramps up and exceeds its UVLO threshold or when the device resets.

. The address values latch when VDD or VEE ramps

with 50kΩ resistor.

to set MIDSPAN operation. The

DIG

C-compatible system.

(see the Typical Application Circuit).

P-P

MAX5945

Detailed Description

The MAX5945 four-port network power controller controls -32V to -60V negative supply rail systems. Use the MAX5945, which is compliant with the IEEE 802.3af standard for PSE in power-over-LAN applications. The MAX5945 provides PD discovery, classification, current limit, both DC and AC load disconnect detections, and other necessary functions for an IEEE 802.3af-compli-

ant PSE. The MAX5945 can be used in either endpoint PSE (LAN switch/router) or midspan PSE (power injector) applications.

The MAX5945 is fully software-configurable and programmable with more than 25 internal registers. The device features an I

C-compatible, 3-wire serial interface and a class-overcurrent detection. The class-overcurrent detection function enables system power man-

Quad Network Power Controller for Power-Over-LAN

12 ______________________________________________________________________________________

Figure 1. MAX5945 Functional Diagram

SHD_

DGNDOSC_INSCL SDAIN SDAOUT

AUTO

MIDSPAN

RESET

AGND

INT

ANALOG

SUPPLY

MONITOR

SERIAL

PORT

INTERFACE

(SPI)

CENTRAL LOGIC UNIT

BIAS/

(CLU)

+10V ANALOG

+5V DIG

VOLTAGE REFERENCES

CURRENT REFERENCES

OSCILLATOR

MONITOR

PORT

STATE

MACHINE

(SM)

AC DISCONNECT

SIGNAL

(ACD)

OPEN CIRCUIT

(OC)

ACD

REFERENCE

CURRENT

A = 3

DETECTION

VOLTAGE PROBING

AND

CURRENT-LIMIT

CONTROL

DETECTION/

CLASSIFICATION

ACD_ENABLE

PWR_EN

CURRENT

LIMIT (ILIM)

FAST

DISCHARGE

CONTROL

CURRENT-LIMIT

DETECTOR

9-BIT ADC

CONVERTER

CURRENT SENSING

100mA

90µA

MAX

DET_

VOLTAGE SENSING

10V

50µA

13V CLAMP

OUT_

GATE_

SENSE_

OVERCURRENT

(OVC)

MAX5945

4mV

FOLDBACK

CONTROL

212mV182mV

agement where it detects a PD that draws more current than the allowable amount for its class. The MAX5945’s extensive programmability enhances system flexibility and allows for uses in other applications.

The MAX5945 has four different operating modes: auto mode, semi-auto mode, manual mode, and shutdown mode (see the Operation Modes section). A special watchdog feature allows the hardware to gracefully take over control if the software/firmware crashes. A cadence timing feature allows the MAX5945 to be used in midspan systems.

The MAX5945 provides input undervoltage lockout, input undervoltage detection, input overvoltage lockout, overtemperature protection, output-voltage slew-rate limit during startup, power-good status, and fault status. The MAX5945’s programmability includes gate-charging current, current-limit threshold, startup timeout, overcurrent timeout, autorestart duty cycle, PD disconnect AC detection threshold and PD disconnect detection timeout.

The MAX5945 communicates with the system microcontroller through an I2C-compatible interface. The MAX5945 features separate input and output data lines (SDAIN and SDAOUT) for use with optocoupler isolation. The MAX5945 is a slave device. Its four address inputs allow 16 unique MAX5945 addresses. A separate INT output and four independent shutdown inputs (SHD_) allow fast interrupt signals between the MAX5945 and the microcontroller. A RESET input allows hardware reset of the device.

Reset

Reset is a condition the MAX5945 enters after any of the following conditions:

• After power-up (VEEand VDDrise above their UVLO thresholds).

• Hardware reset. The RESET input is driven low and up high again any time after power-up.

• Software reset. Writing a 1 into R1Ah[4] any time after power-up.

• Thermal shutdown.

During a reset, the MAX5945 resets its register map to the reset state as shown in Table 30 and latches in the state of AUTO (pin 35) and MIDSPAN (pin 2). During normal operation, changes at the AUTO and MIDSPAN inputs are ignored. While the condition that caused the reset persists (i.e., high temperature, RESET input low, or UVLO conditions) the MAX5945 will not acknowledge any addressing from the serial interface.

Port Reset (R1Ah[3:0])

Set high anytime during normal operation to turn off power and clear the events and status registers of the corresponding port. Port reset only resets the events and status registers.

Operation Modes

The MAX5945 contains four independent but identical state machines to provide reliable and real-time control of the four network ports. Each state machine has four different operating modes: auto, semi-auto, manual, and shutdown. Auto mode allows the device to operate automatically without any software supervision. Semiauto mode, upon request, continuously detects and classifies a device connected to a port but does not power up that port until instructed by software. Manual mode allows total software control of the device and is useful in system diagnostic. Shutdown mode terminates all activities and securely turns off power to the ports. Switching between AUTO, SEMI, or MANUAL mode does not take effect until the part finishes its current task. When the port is set into SHUTDOWN mode, all the port operations are immediately stopped and the port remains idle until SHUTDOWN is exited.

Automatic (AUTO) Mode

Enter automatic (AUTO) mode by forcing the AUTO input high prior to a reset, or by setting R12h[P_ M1,P_M0] to [1,1] during normal operation (see Tables 15 and 15a). In AUTO mode, the MAX5945 performs detection, classification, and powers up the port automatically once a valid PD is detected at the port. If a valid PD is not detected at the port, the MAX5945 repeats the detection routine continuously until a valid PD is detected.

Going into AUTO mode, the DET_EN and CLASS_EN bits are set to high and stay high unless changed by software. Using software to set DET_EN and/or CLASS_EN low causes the MAX5945 to skip detection and/or classification. As a protection, disabling the detection routine in AUTO mode will not allow the corresponding port to power up, unless the DET_BYP (R23H[4]) is set to 1.

The AUTO status is latched into the register only during a reset. Any changes to the AUTO input after reset is ignored.

Semi-Automatic (SEMI) Mode

Enter semi-automatic (SEMI) mode by setting R12h[P_M1,P_M0] to [1,0] during normal operation (see Tables 15 and 15a). In SEMI mode, the MAX5945, upon request, performs detection and/or classification repeatedly but does not power up the port(s), regardless of the status of the port connection.

MAX5945

Quad Network Power Controller

for Power-Over-LAN

______________________________________________________________________________________ 13

MAX5945

Setting R19h[PWR_ON_] (Table 21) high immediately terminates detection/classification routines and turns on power to the port(s).

R14h[DET_EN_, CLASS_EN_] default to low in SEMI mode. Use software to set R14h[DET_EN_, CLASS_EN_] to high to start the detection and/or classification routines. R14h[DET_EN_, CLASS_EN_] are reset every time the software commands a power-off of the port (either through reset or PWR_OFF). In any other case, the status of the bits is left unchanged (including when the state machine turns off the power because a load disconnect or a fault condition is encountered).

MANUAL Mode

Enter MANUAL mode by setting R12h[P_M1,P_M0] to [0,1] during normal operation (see Tables 15 and 15a). MANUAL mode allows the software to dictate any sequence of operation. Write a 1 to both R14h[DET_ EN_] and R14h[CLASS_EN_] start detection and classification operations, respectively, and in that priority order. After execution, the command is cleared from the register(s). PWR_ON_ has highest priority. Setting PWR_ON_ high at any time causes the device to immediately enter the powered mode. Setting DET_EN and CLASS_EN high at the same time causes detection to be performed first. Once in the powered state, the device ignores DET_EN_ or CLASS_EN_ commands.

When switching to MANUAL mode from another mode, DET_EN_, CLASS_EN_ default to low. These bits become pushbutton rather than configuration bits (i.e., writing ones to these bits while in MANUAL mode commands the device to execute one cycle of detection and/or classification. The bits are reset back to zeros at the end of the execution). Putting the MAX5945 into shutdown mode immediately turns off power and halts all operations to the corresponding port. The event and status bits of the affected port(s) are also cleared. In SHUTDOWN mode, the DET_EN_, CLASS_EN_, and PWR_ON_ commands are ignored.

In SHUTDOWN mode, the serial interface operates normally.

Watchdog

R1Dh, R1Eh, and R1Fh registers control watchdog operation. The watchdog function, when enabled, allows the MAX5945 to gracefully take over control or securely shut down the power to the ports in case of software/firmware crashes. Contact the factory for more details.

PD Detection

When PD detection is activated, the MAX5945 probes the output for a valid PD. After each detection cycle, the device sets the DET_END_ bit R04h/05h[3:0] high and reports the detection results in the status registers R0Ch[2:0], R0Dh[2:0], R0Eh[2:0], and R0Fh[2:0]. The DET_END_ bit is reset to low when read through R05h or after a port reset. Both DET_END_ bit status registers are cleared after the port powers down.

A valid PD has a 25kΩ discovery signature characteristic as specified in the IEEE 802.3af standard. Table 1 shows the IEEE 802.3af specification for a PSE detecting a valid PD signature (see the Typical Application Circuit and Figure 2). The MAX5945 can probe and categorize different types of devices connected to the port such as a valid PD, an open circuit, a low resistive load, a high resistive load, a high capacitive load, a positive DC supply, or a negative DC supply.

During detection, the MAX5945 turns off the external MOSFET and forces two probe voltages through the DET_ input. The current through the DET_ input is measured as well as the voltage at OUT_. A two-point slope measurement is used as specified by the IEEE 802.3af standard to verify the device connected to the port. The MAX5945 implements appropriate settling times and a 100ms digital integration to reject 50Hz/60Hz powerline noise coupling.

An external diode, in series with the DET_ input, restricts PD detection to the 1st quadrant as specified by the IEEE 802.3af standard. To prevent damage to non-PD devices and to protect itself from an output short circuit, the MAX5945 limits the current into DET_ to less than 2mA maximum during PD detection.

In midspan mode, the MAX5945 waits 2.2s before attempting another detection cycle after every failed detection. The first detection, however, happens immediately after issuing the detection command.

Power Device Classification

(PD Classification)

During the PD classification mode, the MAX5945 forces a probe voltage (-18V) at DET_ and measures the current into DET_. The measured current determines the class of the PD.

After each classification cycle, the device sets the CL_END_ bit (R04h/05h[7:4]) high and reports the classification results in the status registers R0Ch[6:4], R0Dh[6:4], R0Eh[6:4], and R0Fh[6:4]. The CL_END_ bit is reset to low when read through register R05h or after a port reset. Both Class_END_ bit status registers are cleared after the port powers down.

Quad Network Power Controller for Power-Over-LAN

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