Rainbow Electronics MAX5971А - Manual (Page 13)

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MAX5971A
Single-Port, 40W, IEEE 802.3af/802.3at PSE
Controller with Integrated MOSFET
Simplified Diagram
Detailed Description
The MAX5971A is a single-port, PSE power controller
designed for use in IEEE 802.3af/IEEE 802.3at-compliant
PSE. This device provides PD discovery, classification,
current limit, and DC and AC load-disconnect detec-
tions. The MAX5971A operates automatically without the
need for any software programming and features an inte-
grated 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
MAX5971A provides up to 40W to a single port (Class 5
enabled) and still provides high-capacitance detection
for legacy PDs.
The MAX5971A provides input UVLO, input overvoltage
lockout, overtemperature detection, output voltage slew-
rate limit during startup, and LED status indication.
Reset
The MAX5971A 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 (> 40µs typ.) any time after power-up. The
device exits the reset condition once the EN input is
driven high again.
3) Thermal shutdown. The device enters thermal shut-
down at 150NC. The device exits thermal shutdown and
is reset once the temperature drops below 130NC.
OSC STATUS
MONITOR
OSC
LEGACY
EN
MIDSPAN
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)
THRESHOLD
SETTINGS
ACD
REFERENCE
CURRENT
INTERNAL
MOSFET
INTERNAL
R SENSE
VOLTAGE
SENSING
GATE
DRIVE
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
MAX5971A