MAX5971A Maxim Integrated Products, MAX5971A Datasheet - Page 13

• Manufacturer Part Number: MAX5971A
• Description: Single-Port 40W IEEE 802.3af/at PSE Controller with Integrated MOSFET
• Manufacturer: Maxim Integrated Products

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.
MIDSPAN
LEGACY
AGND
LED
V
EN
EE
Single-Port, 40W, IEEE 802.3af/802.3at PSE
BIAS AND
MONITOR
REGISTER FILE
ANALOG
SUPPLY
______________________________________________________________________________________
Detailed Description
CENTRAL LOGIC
UNIT (CLU)
INTERNAL
SUPPLIES
VOLTAGE
REFERENCES
CURRENT
REFERENCES
Controller with Integrated MOSFET
MACHINE (SM)
PORT STATE
PWM
OSC STATUS
MONITOR
PWMEN
OSC
AC DISCONNECT
SIGNAL (ACD)
GENERATOR
TRIANGLE
WAVE
MAX5971A
The MAX5971A provides input UVLO, input overvoltage
lockout, overtemperature detection, output voltage slew-
rate limit during startup, and LED status indication.
The MAX5971A is reset by any of the following conditions:
1) Power-up. Reset condition is cleared once V
2) Hardware reset. Reset occurs once the EN input is
3) Thermal shutdown. The device enters thermal shut-
CLASSIFICATION
DETECTION AND
CURRENT-LIMIT
above the UVLO threshold.
driven low (> 40µs typ.) any time after power-up. The
device exits the reset condition once the EN input is
driven high again.
down at 150NC. The device exits thermal shutdown and
is reset once the temperature drops below 130NC.
PROBING AND
CONTROL
VOLTAGE
CONTROL
THRESHOLD
SETTINGS
AC DETECTOR
A = 1
ACD
REFERENCE
CURRENT
OVERCURRENT, AND OPEN-
CLASS 5 ENABLE/DISABLE,
AND FOLDBACK CONTROL
CURRENT LIMIT CONTROL
OVERCURRENT AND
CIRCUIT SENSING,
9-BIT ADC
CURRENT LIMIT,
AC DISCONNECT
ILIM1
CURRENT SENSING
DRIVE
GATE
ENABLE
Simplified Diagram
ILIM2
VOLTAGE
SENSING
FOLDBACK
CONTROL
INTERNAL
INTERNAL
MOSFET
R
SENSE
AGND
EE
Reset
DET
OUTP
OUT
rises
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