Rainbow Electronics MAX5971B User Manual

19-5336; Rev 0; 6/10

EVALUATION KIT

AVAILABLE

Single-Port, 40W, IEEE 802.3af/at,

General Description

The MAX5971B is a single-port power controller designed for use in IEEEM 802.3af/at-compliant power-sourcing equipment (PSE). This device provides powered device (PD) discovery, classification, current limit, and DC and AC load-disconnect detections. The MAX5971B supports both fully automatic operation and software programmability, and features an integrated power MOSFET and sense resistor. The device supports detection and classification operation from a single 54V supply. In addition, it supports 2-event classification and new Class 5 classification of high-power PDs. The MAX5971B provides up to 40W to a single port (Class 5 enabled) and still provides high-capacitance detection for legacy PDs.

The device provides four operating modes to suit different system requirements. By default, auto mode allows the device to operate automatically at its default settings without any software. Semiautomatic mode automatically detects and classifies a device connected to the port after initial software activation, but does not power the port until instructed to by software. Manual mode allows total software control of the device and is useful for system diagnostics. Shutdown mode terminates all port activities and securely turns off power to the port.

The IC features an I2C-compatible, 2-wire serial interface, and is fully software-configurable and programmable. The device provides instantaneous readout of port current through the I2C interface. The device’s extensive programmability enhances system flexibility, enables field diagnosis and allows for uses in other, non standard applications.

The device provides input undervoltage lockout (UVLO), input undervoltage detection, input overvoltage lockout, overtemperature protection, output voltage slew-rate limit during startup, and LED status indication. The MAX5971B programmability includes startup timeout, overcurrent timeout, and load-disconnect detection timeout.

The device is available in a space-saving, 28-pin TQFN (5mm x 5mm) power package and is rated for the extended (-40NC to +85NC) temperature range.

Applications

Single-Port PSE End-Point Applications

Single-Port PSE Power Injectors (Midspan Applications)

Switches/Routers

PSE Controller with I2C

Features

S IEEE 802.3af/at Compliant S Up to 40W for Single-Port PSE Applications S Integrated Power MOSFET and Sense Resistor S Supports 54V Single-Supply Operation S PD Detection and Classification S I2C-Compatible, 2-Wire Serial Interface S Instantaneous Readout of Port Current Through

I2C Interface

S Programmable Current Limit for Class 5 PDs S High-Capacitance Detection for Legacy Devices S Supports Both DC and AC Load Removal

Detections

S Current Foldback and Duty-Cycle-Controlled

Current Limit

S LED Indicator for Port Status S Direct Fast-Shutdown Control Capability S Space-Saving, 28-Pin TQFN (5mm x 5mm) Power

Package

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX5971BETI+

+Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad.

-40NC to +85NC

Typical Operating Circuit

-54V

LED

PWMEN

LEGACY

MIDSPAN

OSC

AGND

EE_DIG

MAX5971B

SDA SCL AD0 INT

OUT

OUTP

DET

ILIM1

ILIM2

28 TQFN-EP*

PSE OUTPUT

MAX5971B

SERIAL INTERFACE

IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc.

_______________________________________________________________ Maxim Integrated Products 1

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

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

ABSOLUTE MAXIMUM RATINGS

(Voltages referenced to VEE, unless otherwise noted.)

AGND, DET, LED ..................................................-0.3V to +80V

OUT .......................................................-0.3V to (AGND + 0.3V)

OUTP ........................................................-6V to (AGND + 0.3V)

OSC .........................................................................-0.3V to +6V

EN, PWMEN, MIDSPAN, LEGACY, ILIM1, ILIM2 ....-0.3V to +4V

INT, AD0, SCL, SDA ................................................-0.3V to +6V

Maximum Current into INT and SDA ..................................80mA

MAX5971B

Maximum Current into LED ................................................40mA

Maximum Current into OUT ........................Internally Regulated

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-

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.

................................................................-0.3V to +0.3V

EE_DIG

layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.

ELECTRICAL CHARACTERISTICS

- VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at

AGND

- VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2)

AGND

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

POWER SUPPLIES

Operating Voltage Range V

Supply Current I

CURRENT LIMIT

Current Limit I

Foldback Initial OUT Voltage V

Foldback Final OUT Voltage V

Minimum Foldback Current-Limit Threshold

FLBK_ST

FLBK_END

AGND

LIM

TH_FB

- V

AGND

OUT

measured at AGND in power mode

Maximum I

LOAD

during current-limit conditions, V

OUT

(Note 3)

AGND

starts folding back

AGND

reaches I

OUT

= VEE, all logic inputs unconnected,

allowed

= 0V

- V

OUT

- V

OUT

TH_FB

= V

AGND

Continuous Power Dissipation (TA = +70NC)

28-Pin TQFN (derate 34.5mW/NC above +70NC) ......2758mW

Package Thermal Resistance (Note 1)

BJA ...............................................................................29NC/W

BJC .................................................................................2NC/W

Operating Temperature Range .......................... -40NC to +85NC

Storage Temperature Range ............................ -65NC to +150NC

Junction Temperature .....................................................+150NC

Lead Temperature (soldering, 10s) ................................+300NC

Soldering Temperature (reflow) ......................................+260NC

32 60 V

2.5 4 mA

Class 0, 1, 2, 3 or ICUT = 000

Class 4 or ICUT = 001 684 720 756

Class 5 if ILIM1 = VEE, ILIM2 = unconnected or ICUT = 101

Class 5 if ILIM1 = unconnected, ILIM2 = VEE or ICUT = 110

Class 5 if ILIM1 = VEE, ILIM2 = VEE or ICUT = 111

below which the current limit

400 420 441

807 850 893

855 900 945

902 950 998

27 V

10 V

166 mA

2 ______________________________________________________________________________________

Single-Port, 40W, IEEE 802.3af/at,

PSE Controller with I2C

ELECTRICAL CHARACTERISTICS (continued)

- VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at

AGND

- VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2)

AGND

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

OVERCURRENT

Overcurrent Threshold I

CUT

INTERNAL POWER

DMOS On-Resistance

Power-Off OUT Leakage Current I

OUT_LEAKVEN

SUPPLY MONITORS

VEE Undervoltage Lockout V

VEE Undervoltage Lockout Hysteresis

VEE Overvoltage Lockout V

VEE Overvoltage Lockout Hysteresis

VEE Undervoltage V

Thermal Shutdown Threshold T

Thermal Shutdown Hysteresis T

EE_UVLOVAGND

EE_UVLOH

EE_OVVAGND

EE_OVH

EE_UV

SHD

SHDH

OUTPUT MONITOR

OUT Input Current I

Idle Pullup Current at OUT I

BOUT

DIS

Short to VEE Detection Threshold DCN

Short to VEE Detection Threshold Hysteresis

DCN

Class 0, 1, 2, 3 or ICUT = 000

Class 4 or ICUT = 001 602 634 666

Overcurrent threshold allowed for t P t

, V

FAULT

= 0V (Note 3)

Class 5 if ILIM1 = VEE, ILIM2 = unconnected or ICUT = 101

OUT

Class 5 if ILIM1 = unconnected, ILIM2 = VEE or ICUT = 110

Class 5 if ILIM1 = VEE, ILIM2 = VEE or ICUT = 111

Measured from OUT to VEE, I

OUT

100mA

= VEE, V

OUT

- VEE, V

Port is shutdown if: V

- V

UVLO

EE_UVLOH

- VEE > V

event bit sets if: V

EE_UV

, VEE increasing

EE_UV

TA = +25NC

TA = +85NC

= V

AGND

increasing 28.5 V

AGND

- VEE < V

AGND

EE_OV

, V

AGND

EE_

increasing 62.5 V

- VEE <

Port is shut down and device resets if the junction temperature exceeds this limit, temperature increasing

Temperature decreasing 20

OUT

= V

, probing phases 6

AGND

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

OUTP

OUT

during detection

= V

- V

EE, VOUT

- 2.8V

AGND

decreasing, enabled

351 370 389

710 748 785

752 792 832

794 836 878

0.5 0.9

0.6 1.3

3 V

1 V

40 V

150

200 265

1.5 2.0 2.5 V

220 mV

MAX5971B

_______________________________________________________________________________________ 3

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

ELECTRICAL CHARACTERISTICS (continued)

- VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at

AGND

- VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2)

AGND

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

LOAD DISCONNECT

Minimum load current allowed before

DC Load-Disconnect Threshold I

MAX5971B

AC Load-Disconnect Threshold (Note 4)

Triangular Wave Peak-to-Peak Voltage Amplitude

OSC Pullup/Pulldown Currents I

ACD_EN Threshold V

Load-Disconnect Timer t

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

CLASSIFICATION

Classification Probe Voltage V

Current-Limit Protection I

DCTH

ACTH

AMP

OSC

ACD_EN

DISC

DPH1

DPH2

DLIM

DCP

D_OPEN

DOK

DBAD

ClLIM

disconnect (DC disconnect active), V

= 0V

OUT

Current into DET, for I

DET

< I

ACTH

the port

powers off (AC disconnect active)

Measured at DET, referred to AGND 3.85 4 4.2 V

TRW

Measured at OSC 26 32 39

OSC

- VEE > V

ACD_EN

to activate AC

disconnect

Time from I disconnect active) or I

RSENSE

< I

DCTH DET

(DC

< I

ACTH

(AC disconnect active) to gate shutdown (Note 5)

- V

AGND

during the first detection

DET

phase

- V

AGND

during the second detection

DET

phase

DET

= V

during detection, measure

AGND

current through DET

If V

AGND

- V

OUT

< V

DCP

after the first detection phase a short circuit to AGND is detected.

First point measurement current threshold for open condition

(Note 6) 19 26.5 Detection rejects lower values 15.5 Detection rejects higher values 32

- V

AGND

DET

= V

during classification 16 20 V

DET

, during classification

AGND

measure current through DET

5 7.5 10 mA

115 130 145

270 330 380 mV

300 400 ms

3.8 4 4.2 V

9 9.3 9.6 V

1.50 1.75 2.00 mA

1 V

65 80 mA

4 ______________________________________________________________________________________

Single-Port, 40W, IEEE 802.3af/at,

PSE Controller with I2C

ELECTRICAL CHARACTERISTICS (continued)

- VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at

AGND

- VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2)

AGND

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Class 0, Class 1 5.5 6.5 7.5

Classification current

Classification Current Thresholds I

Mark Event Voltage V

Mark Event Current Limit

DIGITAL INPUTS/OUTPUTS (Voltages Referenced to VEE)

Digital Input Low V Digital Input High V

Internal Input Pullup Current I

Open-Drain Output Low Voltage V Open-Drain Leakage I LED Output Low Voltage V

LED Output Leakage I

PWM Frequency 25 kHz PWM Duty Cycle 6.25 %

TIMING

Startup Time t

Fault Time t

Detection Reset Time t

Detection Time t

Midspan Mode Detection Delay t Classification Time t Mark Event Time Time allowed for mark event 7 9 11 ms

Restart Timer t

Watchdog Clock Period Rate of decrement of the watchdog time 164 ms

Turn-On Delay t

EEUVLO

MARK

IMARK_LIM

LED_LOWILED

LED_LEAK

START

FAULT

DET

DMID

CLASS

DLY

RESTART

thresholds between classes

- V

AGND

= V

DET

current through DET

Pullup current to internal digital supply to set default values

SINK = 10mA

Open-drain high impedance 2

= 10mA, PWM disabled, port power-on 0.8 V

PWM disabled, shutdown mode, V

= 60V

LED

Time during which a current limit set to 420mA is allowed, starts when power is turned on (Note 8)

Maximum allowed time for an overcurrent condition set by I

Time allowed for the port voltage to reset before detection starts

Maximum time allowed before detection is completed

Time allowed for classification 19 23 ms

Time V thresholds before the device operates

Time the device waits before turning on after an overcurrent fault (Note 8)

during mark event 8 10 V

DET

AGND

must be above the V

AGND

Class 1, Class 2 13.0 14.5 16.0 Class 2, Class 3 21 23 25 Class 3, Class 4 31 33 35

Class 4 upper limit (Note 7)

during mark event measure

after startup (Note 8)

CUT

EEUVLO

45 48 51

55 80 mA

2.4 V

3 5 7

50 60 70 ms

2 2.2 2.4 s

0.8 V

0.4 V

80 90 ms

330 ms

5.2 ms

16 x

FAULT

MAX5971B

_______________________________________________________________________________________ 5

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

ELECTRICAL CHARACTERISTICS (continued)

- VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at

AGND

- VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2)

AGND

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

ADC PERFORMANCE (Power-On Mode)

Resolution 9 Bits Range 1.507 A LSB Step Size 2.95 mA

MAX5971B

Gain Error

ADC Absolute Accuracy I Integral Nonlinearity INL 0.3 1.7 LSB Differential Nonlinearity DNL 0.3 1.7 LSB

TIMING CHARACTERISTICS (For 2-Wire Fast Mode)

Serial Clock Frequency f

Bus Free Time Between a STOP and START Condition

Hold Time for a START Condition t Low Period of the SCL Clock t High Period of the SCL Clock t

Setup Time for a Repeated START Condition (Sr)

Data Hold Time t Data in Setup Time t

Rise Time of Both SDA and SCL Signals, Receiving

Fall Time of SDA Transmitting t Setup Time for STOP Condition t

Capacitive Load for Each Bus Line

SCL

BUF

HD,STA

LOW

HIGH

SU,STA

HD,DAT

SU,DAT

SU,STO

TA = +25NC TA = -40NC to +85NC

= 400mA 130 136 142 LSB

OUT

1.3 µs

0.6 µs

1.3 µs

0.6 µs

0 150 ns

100 ns

(Note 9)

(Note 9) 250 ns

(Note 9) 400 pF

20 +

0.1C

0.6 µs

2 4

400 kHz

300 ns

Pulse Width of Spike Suppressed t

Note 2: This device is production tested at T Note 3: Default thresholds are set by the classification result in auto mode. The thresholds are manually software programmable

through the ICUT Register (R2Ah[2:0]). If ILIM1 and ILIM2 are both unconnected, Class 5 detection is disabled. See the Class 5 PD Classification section and Table 3 for details and settings.

Note 4: Default value. The AC load-disconnect threshold can be programmed through the AC_TH register (R23h[2:0]). Note 5: Default value. The load-disconnect time, t Note 6: R

Note 7: If Class 5 is enabled, this value is the classification current threshold from Class 4 to Class 5. Note 8: Default values. The startup, fault, and restart timers can be programmed through the TSTART (R16h[5:4]), TFAULT

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

6 ______________________________________________________________________________________

= (V

DOK

DET during phase 1 and 2 of the detection, respectively.

(R16h[3:2]), and RSRT (R16h[7:6]) registers, respectively.

OUT2

- V

OUT1

)/(I

DET2

- I

(Note 9) 50 ns

= +25°C. Limits to TA = -40°C to +85°C are guaranteed by design.

can be programmed through the TDISC register (R16h[1:0]).

DISC

DET1

). V

OUT1

, V

OUT2

, I

DET2

, and I

represent the voltage at OUT and the current at

DET1

Single-Port, 40W, IEEE 802.3af/at,

PSE Controller with I2C

Typical Operating Characteristics

= +25°C, unless otherwise noted.)

MAX5971B

ANALOG SUPPLY CURRENT

vs. INPUT VOLTAGE

2.7

MEASURED AT AGND

2.6

2.5

SUPPLY CURRENT (mA)

2.4

2.3 32 60

- VEE (V)

AGND

VEE OVERVOLTAGE LOCKOUT

64.0

63.5

63.0

62.5

62.0

61.5

61.0

OVERVOLTAGE LOCKOUT (V)

60.5

60.0

-40 85

MAX5971B toc01

565248444036

vs. TEMPERATURE

TEMPERATURE (°C)

ANALOG SUPPLY CURRENT

vs. TEMPERATURE

2.7

MEASURED AT AGND

2.6

2.5

SUPPLY CURRENT (mA)

2.4

2.3

-40 85 TEMPERATURE (°C)

MAX5971B toc04

6035-15 10

VEE UNDERVOLTAGE LOCKOUT

30.0

29.5

MAX5971B toc02

29.0

28.5

28.0

UNDERVOLTAGE LOCKOUT (V)

27.5

603510-15

27.0

-40 85

INTERNAL FET RESISTANCE

vs. TEMPERATURE

1000

800

600

FET RESISTANCE (mΩ)

400

200

-40 85 TEMPERATURE (°C)

vs. TEMPERATURE

MAX5971B toc03

603510-15

TEMPERATURE (°C)

MAX5971B toc05

603510-15

FOLDBACK CURRENT-LIMIT THRESHOLD

vs. OUTPUT VOLTAGE

800

700

600

500

(mA)

400

RSENSE

300

200

100

0 40

- V

OUT

(V)

AGND

CLASS 4

CLASS 0, 1, 2, 3

302010

MAX5971B toc06

DC DISCONNECT THRESHOLD (mA)

DC DISCONNECT THRESHOLD

vs. TEMPERATURE

7.4

7.2

7.0

6.8

6.6

6.4

-40 85 TEMPERATURE (°C)

603510-15

MAX5971B toc07

_______________________________________________________________________________________ 7

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

Typical Operating Characteristics (continued)

= +25°C, unless otherwise noted.)

OVERCURRENT TIMEOUT (240Ω TO 138Ω)

MAX5971B

0mA

SHORT-CIRCUIT TRANSIENT RESPONSE

20ms/div

MAX5971B toc08

MAX5971B toc10

- V

AGND

20V/div

OUT

200mA/div

- V

AGND

20V/div

OUT

SHORT-CIRCUIT RESPONSE TIME

0mA

20ms/div

EN TO OUT TURN-OFF DELAY

0mA

MAX5971B toc09

MAX5971B toc11

- V

AGND

20V/div

OUT

200mA/div

- V

AGND

20V/div

OUT

200mA/div

OUT

0mA

10µs/div

ZERO-CURRENT DETECTION WAVEFORM

WITH DC DISCONNECT ENABLED

0mA

100ms/div

MAX5971B toc12

5A/div

- V

AGND

20V/div

OUT

100mA/div

OUT

100µs/div

ZERO-CURRENT DETECTION WAVEFORM

WITH AC DISCONNECT ENABLED

0mA

100ms/div

MAX5971B toc13

8 ______________________________________________________________________________________

5V/div

- V

AGND

20V/div

OUT

100mA/div

OUT

Single-Port, 40W, IEEE 802.3af/at,

PSE Controller with I2C

Typical Operating Characteristics (continued)

= +25°C, unless otherwise noted.)

MAX5971B

OVERCURRENT RESTART DELAY

0mA

400ms/div

DETECTION WITH INVALID PD (25kΩ TO 10µF)

0mA

MAX5971B toc14

MAX5971B toc16a

- V

AGND

20V/div

OUT

200mA/div

- V

AGND

1V/div

OUT

1mA/div

OUT

STARTUP WITH A VALID PD

0mA

100ms/div

DETECTION WITH INVALID PD (15kΩ)

0mA

MAX5971B toc15

MAX5971B toc16b

- V

AGND

20V/div

OUT

100mA/div

- V

AGND

5V/div

OUT

1mA/div

OUT

40ms/div

DETECTION WITH INVALID PD (33kΩ)

0mA

100ms/div

_______________________________________________________________________________________ 9

MAX5971B toc16c

AGND

5V/div

OUT

1mA/div

- V

OUT

100ms/div

DETECTION WITH INVALID PD (OPEN CIRCUIT)

0mA

100ms/div

MAX5971B toc16d

AGND

5V/div

OUT

1mA/div

- V

OUT

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

Typical Operating Characteristics (continued)

= +25°C, unless otherwise noted.)

STARTUP IN MIDSPAN WITH A VALID PD

MAX5971B

0mA

DETECTION IN MIDSPAN WITH INVALID PD (33kΩ)

0mA

100ms/div

MAX5971B toc17

MAX5971B toc18b

- V

AGND

20V/div

OUT

100mA/div

- V

AGND

5V/div

OUT

1mA/div

OUT

DETECTION IN MIDSPAN WITH INVALID PD (15kΩ)

0mA

400ms/div

DETECTION IN OUTPUT SHORTED TO AGND

0mA

MAX5971B toc18a

MAX5971B toc19

AGND

5V/div

OUT

1mA/div

AGND

5V/div

OUT

1mA/div

- V

OUT

400ms/div

CLASSIFICATION WITH DIFFERENT PD CLASSES

(0 TO 3)

0mA

40ms/div

MAX5971B toc20a

CLASS 3

CLASS 2

CLASS 1 CLASS 0

AGND

10V/div

OUT

10mA/div

- V

CLASSIFICATION WITH DIFFERENT PD CLASSES

OUT

0mA

40ms/div

(4 AND 5)

40ms/div

MAX5971B toc20b

CLASS 5

CLASS 4

10 _____________________________________________________________________________________

AGND

10V/div

OUT

20mA/div

- V

OUT

Single-Port, 40W, IEEE 802.3af/at,

PSE Controller with I2C

Typical Operating Characteristics (continued)

= +25°C, unless otherwise noted.)

MAX5971B

STARTUP USING 2-EVENT CLASSIFICATION

WITH A VALID PD

0mA

100ms/div

LED DETECTION FAULT WITH PWM DISABLED

0mA

MAX5971B toc22b

- V

AGND

10V/div

OUT

500mA/div

MAX5971B toc21

- V

AGND

OUT

20V/div

OUT

100mA/div

LED OVERCURRENT FAULT WITH PWM ENABLED

OUT

0mA

MAX5971B toc23a

LED DETECTION FAULT WITH PWM ENABLED

0mA

200ms/div

MAX5971B toc22a

LED OVERCURRENT FAULT WITH PWM DISABLED

- V

AGND

OUT

50V/div

OUT

500mA/div

0mA

- V

AGND

10V/div

OUT

500mA/div

- V

AGND

20V/div

OUT

LED

MAX5971B toc23b

- V

AGND

50V/div

OUT

500mA/div

OUT

- V

AGND

LED

20V/div

200ms/div

LED PWM TIMING: MINIMUM DUTY

CYCLE (DEFAULT)

OmA

10µs/div

MAX5971B toc24a

AGND - V

50V/div

OUT

500mA/div

AGND - V

20V/div

OUT

LED

- V

AGND

LED

20V/div

LED PWM TIMING: MAXIMUM DUTY

CYCLE (PROGRAMMABLE)

OmA

10µs/div

200ms/div

MAX5971B toc24b

AGND - V

50V/div

OUT

500mA/div

AGND - V

20V/div

OUT

LED

AGND

20V/div

- V

LED

______________________________________________________________________________________ 11

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

Pin Configuration

TOP VIEW

N.C.

OSC

4 5 6 7

ILIM1

LED

*EP

ILIM2

N.C.

PWMEN

I.C.

MIDSPAN

LEGACY

EE_DIG

AD0

INT

SCL

SDA

MAX5971B

*CONNECT TO V

N.C.

DET

N.C.

OUTP

OUT

N.C.

AGND

2021 19 17 16 15

1 2

MAX5971B

THIN QFN

Pin Description

PIN NAME FUNCTION

1, 2, 3 V

4 ILIM1

Analog Low-Side Supply Input. Bypass with an external 100V, 47FF capacitor in parallel with a 100V, 0.1FF ceramic capacitor between AGND and VEE.

Class 5 Current-Limit Digital Adjust 1. Referenced to VEE. ILIM1 is internally pulled up to the digital supply. Use ILIM1 with ILIM2 to enable Class 5 operation and to adjust the Class 5 current-limit value. See the Electrical Characteristics table and Table 3 in the Class 5 PD Classification section for details.

Class 5 Current-Limit Digital Adjust 2. Referenced to VEE. ILIM2 is internally pulled up to the digital

5 ILIM2

supply. Use ILIM2 with ILIM1 to enable Class 5 operation and to adjust the Class 5 current-limit value. See the Electrical Characteristics table and Table 3 in the Class 5 PD Classification section for details.

PWM Control Logic Input. Referenced to VEE. PWMEN is internally pulled up to the digital sup-

6 PWMEN

ply. Leave unconnected to enable the internal PWM to drive the LED pin. Force low to disable the internal PWM.

Detection Collision Avoidance Logic Input. Referenced to VEE. MIDSPAN is internally pulled up

7 MIDSPAN

to the digital supply. Leave unconnected to activate the detection collision avoidance circuitry for midspan PSE systems. Force low to disable this function for an end-point PSE system. The MIDSPAN logic level latches after the device is powered up or after a reset condition.

8 SDA

2-Wire Serial Interface Input/Output Data Line. Referenced to VEE. Connect to VEE if the I2C interface is not used.

12 _____________________________________________________________________________________

Single-Port, 40W, IEEE 802.3af/at,

PSE Controller with I2C

Pin Description (continued)

PIN NAME FUNCTION

9 SCL

11 AD0

12 V

13 LEGACY

14 EN

15 I.C. Internally Connected. Connect I.C. to VEE.

16, 18, 20,

22, 24, 28

17 LED

INT

EE_DIG

N.C. No Connection. Not internally connected. Leave N.C. unconnected.

2-Wire Serial Interface Input Clock Line. Referenced to VEE. Connect to VEE if the I2C interface is not used.

Open-Drain Interrupt Output. Referenced to VEE. INT is pulled low whenever an interrupt is sent to the microcontroller. See the Interrupt section for details. Connect to VEE if the I2C interface is not used.

Address Input. Referenced to VEE. AD0 is used to form the lower part of the device address. See the Device Address section and Table 5 for details. Connect to VEE if the I2C interface is not used.

Digital Low-Side Supply Input. Connect to VEE externally.

Legacy Detection Logic Input. Referenced to VEE. LEGACY is internally pulled up to the digital supply. Leave unconnected to activate the legacy PD detection. Force low to disable this function. The LEGACY logic level latches after the device is powered up or after a reset condition.

Enable Input. Referenced to VEE. EN is internally pulled up to the digital supply. Leave unconnected to enable the device. Force low for at least 40Fs to reset the device. The MIDSPAN, OSC, and LEGACY states latch-in when the reset condition is removed (low-to-high transition). Bypass EN to VEE with a 1nF ceramic capacitor.

LED Indicator Open-Drain Output. Referenced to VEE. LED can sink 10mA and can drive an external LED directly. Blinking functionality is provided to signal different conditions (see the PWM and LED Signals section). Connect LED to AGND externally (see Figures 15 and 16) or to an external supply (if available) through a series resistance.

MAX5971B

AC-Disconnect Triangular Wave Output. Bypass with a 100nF (Q10% tolerance) external capacitor

19 OSC

21 AGND High-Side Supply Input

23 DET

25 OUTP

26, 27 OUT

— EP Exposed Pad. Connect EP to VEE externally. See the Layout Procedure section for details.

______________________________________________________________________________________ 13

to VEE to enable the AC disconnect function. Connect OSC to VEE to disable the AC disconnect function and to activate the DC disconnect function. The OSC state latches after the device is powered up or after a reset condition.

Detection/Classification Voltage Output. DET is used to set the detection and classification probe voltages and for the AC current sensing when using the AC disconnect function. To use the AC disconnect function, place a 1kI and 0.47FF RC series in parallel with the external protection diode to OUTP (see Figure 16).

Port Pullup Output. OUTP is used to pull up the port voltage to AGND when needed. If AC disconnect is used, connect OUTP to the anode of the AC-blocking diode. If AC disconnect is not used, connect OUTP to OUT (see Figures 15 and 17). Bypass OUTP to AGND with a 100V, 0.1FF ceramic capacitor.

Integrated MOSFET Output. If DC disconnect is used, connect the port output to OUTP (see Figures 15 and 17). If the AC disconnect function is used, connect OUT to the cathode of the AC-blocking diode (see Figure 16).

Single-Port, 40W, IEEE 802.3af/at, PSE Controller with I2C

Simplified Diagram

SCL SDA

ADO

SERIAL PORT

INTERFACE (SPI)

MAX5971B

LEGACY

MIDSPAN

AGND

LED

INT

ANALOG

BIAS AND

SUPPLY

MONITOR

CENTRAL LOGIC

UNIT (CLU)

INTERNAL SUPPLIES

VOLTAGE REFERENCES

CURRENT REFERENCES

OSC STATUS

MONITOR

PORT STATE

MACHINE (SM)

PWM

OSC

TRIANGLE

WAVE

GENERATOR

AC DISCONNECT

SIGNAL (ACD)

MAX5971B

VOLTAGE

PROBING AND

CURRENT-LIMIT

CONTROL

DETECTION AND CLASSIFICATION

CONTROL

A = 1

AC DETECTOR

THRESHOLD

SETTINGS

CURRENT SENSING

9-BIT ADC

AC DISCONNECT

ENABLE

POWER ENABLE

ACD REFERENCE CURRENT

CURRENT-LIMIT,

OVERCURRENT, AND OPEN-

CIRCUIT SENSING,

AND FOLDBACK CONTROL

CLASS 5 ENABLE/DISABLE,

OVERCURRENT AND

CURRENT-LIMIT CONTROL

GATEDRIVE

CONTROL

VOLTAGE SENSING

FOLDBACK CONTROL

INTERNAL

AGND

MOSFET

SENSE

DET

OUTP

OUT

ILIM2

ILIM1PWMEN

Detailed Description

The MAX5971B is a single-port power controller designed for use in IEEE 802.3af/802.3at-compliant PSE. This device provides PD discovery, classification, current limit, and DC and AC load-disconnect detections. The MAX5971B supports both fully automatic operation and software programmability, and features an integrated

of port current through the I2C interface. The MAX5971B provides input undervoltage lockout (UVLO), input undervoltage detection, input overvoltage lockout, overtemperature protection, output voltage slew-rate limit during startup, and LED status indication. The MAX5971B programmability includes startup timeout, overcurrent timeout, and load-disconnect detection timeout.

power MOSFET and sense resistor. The device also supports new Class 5 and 2-event classification for detection and classification of high-power PDs. The MAX5971B provides up to 40W to a single port (Class 5 enabled), and still provides high-capacitance detection for legacy PDs.

The MAX5971B features an I2C-compatible, 2-wire serial interface, and is fully software configurable and programmable. The device provides instantaneous readout

14 _____________________________________________________________________________________

The MAX5971B is reset by any of the following conditions:

1) Power-Up. Reset condition is cleared once VEE rises above the UVLO threshold.

2) Hardware Reset. Reset occurs once the EN input is driven low (> 40Fs, typ) any time after power-up. The device exits the reset condition once the EN input is driven high again.

Reset

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