LTC4269CDKD-1#PBF Linear Technology, LTC4269CDKD-1#PBF Datasheet - Page 16

• Manufacturer Part Number: LTC4269CDKD-1#PBF
• Description: IC PD/OPTO FLYBACK CTRLR 32-DFN
• Manufacturer: Linear Technology
• Type: Power Over Ethernet (PoE)r

Specifications of LTC4269CDKD-1#PBF

• Applications: Power Interface Switch for Power Over Ethernet (PoE) Devices
• Voltage - Supply: 14 V ~ 16 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 32-DFN
• Current - Supply: 1.35mA
• Interface: IEEE 802.3af
• Controller Type: Powered Device Interface Controller (PD)
• Input Voltage: 60V
• Supply Current: 6.4mA
• Digital Ic Case Style: DFN
• No. Of Pins: 32
• Duty Cycle (%): 88%
• Frequency: 100kHz
• Operating Temperature Range: 0°C To +70°C
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Pin Count: 32
• Mounting: Surface Mount
• Package Type: DFN EP
• Case Length: 7mm
• Screening Level: Commercial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4269-1
To control the power-on surge currents in the system, the
LTC4269-1 provides a fi xed inrush current, allowing C1 to
ramp up to the line voltage in a controlled manner.
The LTC4269-1 keeps the PD inrush current below the
PSE current limit to provide a well controlled power-up
characteristic that is independent of the PSE behavior.
This ensures a PD using the LTC4269-1 interoperability
with any PSE.
TURN-ON/ TURN-OFF THRESHOLD
The IEEE 802.3af/at specifi cation for the PD dictates a
maximum turn-on voltage of 42V and a minimum turn-off
voltage of 30V. This specifi cation provides an adequate
voltage to begin PD operation, and to discontinue PD op-
eration when the input voltage is too low. In addition, this
specifi cation allows PD designs to incorporate an ON/OFF
hysteresis window to prevent start-up oscillations.
The LTC4269-1 features an ON/OFF hysteresis window (see
Figure 5) that conforms with the IEEE 802.3af/at specifi ca-
tion and accommodates the voltage drop in the cable and
input diode bridge at the onset of the inrush current.
Once C1 is fully charged, the LTC4269-1 turns on is internal
MOSFET and passes power to the PD load. The LTC4269-1
continues to power the PD load as long as the input voltage
APPLICATIONS INFORMATION
16
PSE
TO
Figure 5. LTC4269-1 ON/OFF and Overvoltage Lockout
V
LTC4269-1
PORTN
V
VOLTAGE
0V TO ON*
>ON*
<OFF*
>OVLO
*INCLUDES ON/OFF HYSTERESIS
ON THRESHOLD 36.1V
OFF THRESHOLD 30.7V
OVLO THRESHOLD 71.0V
PORTP
OVERVOLTAGE
ON/OFF AND
LOCKOUT
CIRCUIT
– V
PORTN
POWER MOSFET
LTC4269-1
OFF
OFF
OFF
ON
V
PORTP
V
NEG
CURRENT-LIMITED
TURN ON
+
42691 F05
C1
5μF
MIN
LOAD
PD
does not fall below the OFF threshold. When the LTC4269-1
input voltage falls below the OFF threshold, the PD load
is disconnected, and classifi cation mode resumes. C1
discharges through the LTC4269-1 circuitry.
COMPLEMENTARY POWER GOOD
When LTC4269-1 fully charges the load capacitor (C1),
power good is declared and the LTC4269-1 load can safely
begin operation. The LTC4269-1 provides complementary
power good signals that remain active during normal op-
eration and are de-asserted when the input voltage falls
below the OFF threshold, when the input voltage exceeds
the overvoltage 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. When power good is declared and active, the PWRGD
pin is high impedance with respect to V
14V clamp limits the PWRGD pin voltage. Connecting the
PWRGD pin to the UVLO prevents the DC/DC converter
Figure 6. LTC4269-1 Power Good Functional and State Diagram
V
V
PORTN
PORTN
5
6
LTC4269-1
NEG
ON/OFF
OVLO
BOLD LINE INDICATES HIGH CURRENT PATH
which can interface directly with the UVLO
TSD
POWER
GOOD
AND NOT IN THERMAL SHUTDOWN
NOT
OR THERMAL SHUTDOWN
CONTROL
CIRCUIT
ON < V
INRUSH COMPLETE
V
V
PORTP
PORTP
PORTP
> OVLO
< OFF
< OVLO
POWER
GOOD
NEG
42691 F06
. An internal
30
29
27
26
PWRGD
PWRGD
V
V
NEG
NEG
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