Rainbow Electronics MAX5971B - Manual (Page 14)

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MAX5971B
Single-Port, 40W, IEEE 802.3af/at,
PSE Controller with I 2 C
Simplified Diagram
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
power MOSFET and sense resistor. The device also sup-
ports 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 I
2 C-compatible, 2-wire serial
interface, and is fully software configurable and pro-
grammable. The device provides instantaneous readout
of port current through the I 2 C interface. The MAX5971B
provides input undervoltage lockout (UVLO), input under-
voltage detection, input overvoltage lockout, overtem-
perature protection, output voltage slew-rate limit dur-
ing startup, and LED status indication. The MAX5971B
programmability includes startup timeout, overcurrent
timeout, and load-disconnect detection timeout.
Reset
The MAX5971B is reset by any of the following conditions:
1) Power-Up. Reset condition is cleared once V
EE 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.
OSC STATUS
MONITOR
SERIAL PORT
INTERFACE (SPI)
OSC
ADO
LEGACY
EN
MIDSPAN
INT
PORT STATE
MACHINE (SM)
REGISTER FILE
ANALOG
BIAS AND
SUPPLY
MONITOR
VOLTAGE
PROBING AND
CURRENT-LIMIT
CONTROL
DETECTION AND
CLASSIFICATION
CONTROL
CENTRAL LOGIC
UNIT (CLU)
AC DETECTOR
PWM
AC DISCONNECT
SIGNAL (ACD)
POWER ENABLE
THRESHOLD
SETTINGS
ACD
REFERENCE
CURRENT
INTERNAL
MOSFET
INTERNAL
R SENSE
VOLTAGE
SENSING
GATE-
DRIVE
CONTROL
CURRENT-LIMIT,
OVERCURRENT, AND OPEN-
CIRCUIT SENSING,
AND FOLDBACK CONTROL
CLASS 5 ENABLE/DISABLE,
OVERCURRENT AND
CURRENT-LIMIT CONTROL
ILIM1 PWMEN
LED
V EE
AGND
ILIM2
9-BIT ADC
AGND
OUTP
OUT
FOLDBACK
CONTROL
DET
TRIANGLE
WAVE
GENERATOR
AC DISCONNECT
ENABLE
A = 1
VOLTAGE
REFERENCES
CURRENT
REFERENCES
INTERNAL
SUPPLIES
CURRENT SENSING
MAX5971B
SCL SDA