LTC4265 LINER [Linear Technology], LTC4265 Datasheet - Page 11

• Manufacturer Part Number: LTC4265
• Description: IEEE 802.3at High Power PD Interface Controller with 2-Event Classifi cation Recognition
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
Once C1 is fully charged, the LTC4265 turns on is internal
MOSFET and passes power to the PD load. The LTC4265
continues to power the PD load as long as the input volt-
age does not fall below the UVLO threshold. When the
LTC4265 input voltage falls below the UVLO threshold, the
PD load is disconnected, and classifi cation mode resumes.
C1 discharges through the LTC4265 circuitry.
COMPLEMENTARY POWERGOOD
When LTC4265 fully charges the load capacitor (C1), power
good is declared and the LTC4265 load can safely begin
operation. The LTC4265 provides complementary power
good signals that remain active during normal operation
and are de-asserted when the input voltage falls below
the UVLO threshold, when the input voltage exceeds the
over-voltage lockout (OVLO) threshold, or in the event of
a thermal shutdown. See Figure 6.
The PWRGD pin features an open collector output refer-
enced to V
pin of a DC/DC converter product. When power good is
declared and active, the PWRGD pin is high impedance
with respect to V
DC/DC converter from an excessive voltage.
The active low PWRGD pin connects to an internal, open
drain MOSFET referenced to V
to the shutdown pin of a DC/DC converter product. When
power good is declared and active, the PWRGD pin is low
impedance with respect to V
OUT
which can interface directly with the “Run”
OUT
. An internal 14V clamp protects the
IN
IN
.
and can interface directly
PWRGD PIN WHEN SHDN IS INVOKED
In PD applications where an auxiliary power supply invokes
the SHDN feature, the PWRGD pin becomes high imped-
ance. This prevents the PWRGD pin that is connected to
the “Run” pin of the DC/DC converter from interfering
with the DC/DC converter operations when powered by
an auxiliary power supply.
V
V
Figure 6. LTC4265 Power Good Functional and State Diagram
IN
IN
5
6
LTC4265
OVLO
UVLO
BOLD LINE INDICATES HIGH CURRENT PATH
TSD
ON
POWER
GOOD
NOT
AND NOT IN THERMAL SHUTDOWN
OR THERMAL SHUTDOWN
CONTROL
CIRCUIT
INRUSH COMPLETE
ON < GND < OVLO
GND < UVLO
GND > OVLO
POWER
GOOD
LTC4265
4265 F06
10
9
8
7
PWRGD
PWRGD
V
V
OUT
OUT
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