LT4321HUF Datasheet PDF - Linear Technology

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LT4321HUF
Linear Technology

Part Number LT4321HUF
Description PoE Ideal Diode Bridge Controller
Page 12 Pages


LT4321HUF datasheet pdf
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LT4321
PoE Ideal Diode Bridge
Controller
Features
n Reduces Heat, Eliminates Thermal Design Problems
n Maximizes Power Efficiency
n Less than 800µA Quiescent Operating Current
n Fully Compatible with IEEE 802.3 Detection and
Classification
n IEEE 802.3 Compliant When Paired with a Powered
Device (PD) Controller
n Works with 2-Pair and 4-Pair PoE Applications
n Compatible with PoE, PoE+, and LTPoE++™
n 100V Absolute Maximum Voltage
n H-Grade Version Operates Up to 125°C
n 16-Lead 4mm × 4mm QFN Package
Applications
n PoE/PoE+/ LTPoE++ Powered Devices
n DC Polarity Correction and Ideal Diode-ORing of
Telecom Supplies
Description
The LT®4321 is a dual ideal diode bridge controller that
enables a Power over Ethernet (PoE) powered device
(PD) to receive power in either voltage polarity from
RJ-45 data pairs, spare pairs, or both. The LT4321 and
eight N-channel MOSFETs replace the eight diodes in a
passive PoE rectifier bridge. The LT4321 eases thermal
design and increases delivered power.
An internal charge pump allows an all-NMOS bridge
eliminating larger and more costly PMOS switches. The
LT4321 works with 2-pair and 4-pair applications. High
impedance input sense pins prevent reverse current on
unused pairs. If the power source fails or is shorted, a
fast turn-off minimizes reverse current transients. Unlike
discrete ideal bridge solutions, the LT4321 will operate
through transients without enabling the MOSFETs on
unpowered pairs.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and LTPoE++ are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Typical Application
Powered Device for PoE (to 13W), PoE+ (to 25.5W), or Linear LTPoE++ (to 90W) Systems
1
DATA
PAIRS
2
3
6
4
SPARE
PAIRS
5
7
8
TG12 BG12
IN12
BG36 TG36
OUTP
EN
IN36 LT4321
IN45
EN
IN78 OUTN
BG45 TG45
TG78 BG78
0.1µF
SMAJ60A
+
10µF
VPORT HSGATE HSSRC
LT4275
PWRGD
GND
VIN
ISOLATED
POWER
SUPPLY
RUN
GND
+
VOUT
4321 TA01
For more information www.linear.com/LT4321
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LT4321
Absolute Maximum Ratings
(Notes 1, 2)
OUTP-OUTN.............................................. –0.3V to 100V
IN12, IN36, IN45, IN78........................ –2V to OUTP + 2V
BG12, BG36, BG45, BG78 Voltages........... –0.3V to 100V
TG12, TG36, TG45, TG78
Voltages ........................................ –0.3V to OUTP + 12V
TG12-IN12 Voltage.......................................–0.3V to 12V
TG36-IN36 Voltage......................................–0.3V to 12V
TG45-IN45 Voltage......................................–0.3V to 12V
TG78-IN78 Voltage.......................................–0.3V to 12V
EN, EN,...................................................... –0.3V to 100V
Operating Ambient Temperature Range
LT4321I.................................................–40°C to 85°C
LT4321H.............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Pin Configuration
TOP VIEW
TG36 1
IN36 2
IN45 3
TG45 4
16 15 14 13
12
17
OUTN
11
10
9
5678
OUTP
EN
EN
OUTN
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
TJMAX = 125°C, θJC = 4.5°C/W
EXPOSED PAD (PIN 17) IS OUTN, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT4321IUF#PBF
LT4321IUF#TRPBF
4321
16-Lead 4mm × 4mm Plastic QFN
–40°C to 85°C
LT4321HUF#PBF
LT4321HUF#TRPBF
4321
16-Lead 4mm × 4mm Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
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LT4321
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, OUTP = 20V to 80V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX
Operating Supply Range
|IN12-IN36|, |IN45-IN78|, OUTP
l 20
80
VUVLO
IS(DET)
IS(OFF)
IS(ON)
Undervoltage Lockout
OUTP-OUTN
l 15 17 18
Total Supply Current in Detect Region OUTP < 10V
l 0.8 5
Total Supply Current in Shutdown
Total Operating Supply Current
Top Gate Drive
OUTP > 12V, EN < VIL and EN > VIH
l
32 60
EN > VIH or EN < VIL, OUTP > 20V l 0.5 0.8
INn = OUTP +
TGn (Note 3)
∆VSD(MAX)
+
5mV,
10µA
Out
of
l
7.7
9.5
11
VBG Bottom Gate Drive
Top Gate Pull-Up Current
10µA Out of BGn (Note 3)
TGn = INn (Note 3)
l 10 11.5 13
l 50 120 250
Top Gate Pull-Down Current
INn = OUTP – 0.25V; TGn – INn = 5V
l 1.25
Bottom Gate Pull-Up Current
Bottom Gate Pull-Down Current
BGn < VBG (Note 3)
BGn = 5V
l 15 30 45
l3
EN Pull-Up Resistance (Active Low)
OUTP = 55V
l 160 250 310
EN Pull-Down Resistance (Active High) OUTP = 55V
l 160 250 310
VIH
VIL
VENOC
∆VSD
Digital Input High
Digital Input Low
EN Open Circuit Voltage
Topside Forward Regulation Voltage
Bottom Comparator Turn-On Threshold
EN, EN
EN, EN
OUTP = 55V
INn - OUTP
INn - OUTN
l 2.6
l 0.5
l 2 2.5 3
l2
10 18
l –30
–15
0
Bottom Comparator Turn-Off Threshold INn - OUTN
l2
15 30
UNITS
V
V
µA
µA
mA
V
V
µA
mA
µA
mA
V
V
V
mV
mV
mV
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: Referenced with respect to OUTN unless otherwise specified.
Note 3: All conditions for external MOSFET turn on must be met. See
Table 1 and Table 2.
For more information www.linear.com/LT4321
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LT4321
Typical Performance Characteristics
Total Supply Current in Shutdown
40
IN12 = IN45 = VIN
35 IN36 = IN78 = 0V
30
25
20
15
10 –40°C
25°C
5 100°C
125°C
0
0 10 20 30 40 50 60 70 80
VIN (V)
4321 G01
Total Supply Current in Ideal
Bridge Mode, 2-Pair
700 IN12 = VIN
600
IN36 = 0
FLOAT IN45, IN78
EN = EN = 0
500
400
300
200 –40°C
100
25°C
100°C
125°C
0
0 10 20 30 40 50 60 70 80
VIN (V)
4321 G02
Input Pin Current
1.0
OUTP = 80V
0.5
0.0
–0.5
–1.0
0
–40°C
25°C
100°C
125°C
20 40 60
INn (V)
80
4321 G04
EN Open Circuit Voltage
3.0
2.5
2.0
1.5
1.0
0.5
0
0
–40°C
25°C
100°C
125°C
10 20 30 40 50 60 70 80
OUTP (V)
4321 G05
BGn Pull-Up Strength
35
30
25
20
15
10
5
0
02
468
VBGn (V)
10 12
4321 G07
4
TG Pull-Down Strength
3.5
OUTP = 20V
3.0 OUTP = 80V
2.5
2.0
1.5
1.0
0.5
0
0
2
IN45 = IN78 = FLOAT
EN = OUTP
IN12 = OUTP –250mV
IN36 = OUTN –50mV
4 6 8 10
∆VTGATE (V)
4321 G08
For more information www.linear.com/LT4321
Total Supply Current in Ideal
Bridge Mode, 4-Pair
700 IN12 = IN45 = VIN
600
IN36 = IN78 = 0
EN = EN = 0
500
400
300
200 –40°C
100
25°C
100°C
125°C
0
0 10 20 30 40 50 60 70 80
VIN (V)
4321 G03
BGn Pull-Down Strength
18
16
14
12
10
8
6
4
2
0
02
468
VBGn (V)
10 12
4321 G06
TG Pull-Up Strength
180 IN12 – IN36 = 20V
160 IN12 – IN36 = 30V
IN12 – IN36 = 80V
140
120
100
80
60
40
20
0
0
IN45 = IN78 = FLOAT
EN = OUTP
246
∆VTGATE (V)
8 10
4321 G09
4321f



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LT4321HUF PoE Ideal Diode Bridge Controller LT4321HUF
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