- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄179919 > LTC4259ACGW-1#PBF (LINEAR TECHNOLOGY CORP) Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C PDF資料下載
參數(shù)資料
| 型號： | LTC4259ACGW-1#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 電源管理 |
| 英文描述： | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
| 中文描述： | 4-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO36 |
| 封裝： | 0.300 INCH, LEAD FREE, PLASTIC, SSOP-36 |
| 文件頁數(shù)： | 14/32頁 |
| 文件大?。?/td> | 416K |
| 代理商： | LTC4259ACGW-1#PBF |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁當(dāng)前第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁
LTC4259A-1
21
4259a1fa
DC DISCONNECT
DC disconnect monitors the sense resistor voltage when-
ever the power is on to make sure that the PD is drawing
the minimum specified current. The disconnect timer
counts up whenever port current is below 7.5mA (typ). If
the tDIS timer runs out, the corresponding port will be
turned off and the disconnect bit in the fault register will be
set. If the undercurrent condition goes away before the
tDIS timer runs out, the timer will reset. The timer will start
counting from the beginning if the undercurrent condition
occurs again. The undercurrent circuit includes a glitch
filter to filter out noise.
The DC disconnect feature can be disabled by clearing the
corresponding DC Discon Enable bits in the Disconnect
register (13h). The tDIS timer duration can be programmed
by bits 1 and 0 of register 16h.
The LTC4259A-1 implements a variety of current sense
and limit thresholds to control current flowing through
the port. Figure 17 is a graphical representation of these
thresholds and the action the LTC4259A-1 takes when
currrent crosses the thresholds.
falls below IACDMIN) due to the removal of the PD, the dis-
connect timer counts up. If the impedance remains high
(AC current remains below IACDMIN), the disconnect timer
counts to tDIS, the port is turned off and the port’s discon-
nect bit in the Fault Register is set. If the impedance falls
(AC current rises above IACDMIN) before the maximum
count of the disconnect timer, the timer resets and the port
remains powered.
Like DC disconnect, AC disconnect can also be disabled by
clearing the corresponding AC Discon Enable bits in the
Disconnect register (13h). AC disconnect is also affected
by the tDIS duration programmed in register 16h.
Unlike DC disconnect, AC disconnect has no continuous
time output to the timer. Rather, AC disconnect will reset
the timer once every cycle, 1/fOSCIN, of the OSCIN signal if
the port draws more than IACDMIN during that period.
Because of this behavior, the time to turn off the port after
PD removal, tDIS, may vary by up to one cycle of OSCIN
(1/fOSCIN) from the delay programmed with the tDIS1 and
tDIS0 bits. Note that AC disconnect and DC disconnect
signals that reset the tDIS timer are ORed together. Thus on
a port where both disconnect modes are enabled, either
disconnect sensing method can keep the port
powered even if the other reports that there is no PD
connected.
The LTC4259A-1 provides a higher AC disconnect thresh-
old, IACDMIN (see Electrical Characteristics) than the
LTC4259A. This reduces the port impedance that the
LTC4259A-1’s AC disconnect circuitry senses as the ab-
sence of a PD. Consequently, in the same application
circuit the LTC4259A-1 will have less sensitivity to parasitics
like leakage and stray capacitance than an LTC4259A.
Both the LTC4259A and LTC4259A-1 (used with the
recommended application circuit) meet all the AC discon-
nect requirements of 802.3af standard. Because the
LTC4259A-1 offers improved performance, Linear Tech-
nology recommends the LTC4259A-1 for new designs and
as a replacement for the LTC4259A in existing designs.
The AC disconnect circuitry senses the port and Power
over Ethernet connection from the DETECT pins. Connect
a 0.47
F 100V X7R capacitor (CDET) and a 1k resistor
(RDET) from the port’s DETECT pin to the port’s output as
shown in Figure 18. This provides an AC path for sensing
APPLICATIO S I FOR ATIO
WU
UU
Figure 17. LTC4259A-1 Current Sense and Limits
0mA
0mV
100mA
CURRENT
RS = 0.5
DC DIS-
CONNECT
CUT
(ICUT)
LIMIT
(ILIM)
SHORT
CIRCUIT
EFFECT
SENSE
n
VOLTAGE
50mV
200mA
100mV
300mA
150mV
400mA
200mV
500mA
250mV
600mA
300mV
CURRENT
LIMIT
PORT OFF IN tICUT
OR tSTART
CURRENT LIMIT
IN 1
s
NORMAL
OPERATION
PORT OFF IN tDIS
4259A F17
AC DISCONNECT
AC disconnect is an alternate method of sensing the pres-
ence or absence of a PD by monitoring the port impedance.
The LTC4259A-1 forces a signal, amplified from the OSCIN
pin, out of the DETECT pins and onto the Power over Eth-
ernet connection. It calculates the connection impedance
from ohm’s law, ZPORT = VAC/IAC. Like DC disconnect, the
AC disconnect sensing circuitry controls the disconnect
timer. When the connection impedance rises (AC current
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC4259ACGW-1#TRPBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
| LTC4259AIGW-1#PBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: -40°C to +85°C |
| LTC4259AIGW-1#TRPBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: -40°C to +85°C |
| LTC4259ACGW#PBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
| LTC4259ACGW#TRPBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC4259AIGW-1 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect |
| LTC4259AIGW-1#PBF | 功能描述:IC CTRLR POE QUAD AC DISC 36SSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標(biāo)準(zhǔn)包裝:2,450 系列:- 控制器類型:SPI 總線至 I²C 總線橋接 接口:I²C，串行，SPI 電源電壓:2.4 V ~ 3.6 V 電流 - 電源:11mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND |
| LTC4259AIGW-1#TRPBF | 功能描述:IC CTRLR POE QUAD AC DISC 36SSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標(biāo)準(zhǔn)包裝:2,450 系列:- 控制器類型:SPI 總線至 I²C 總線橋接 接口:I²C，串行，SPI 電源電壓:2.4 V ~ 3.6 V 電流 - 電源:11mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND |
| LTC4259CGW-ES | 制造商:LINEAR_TECH 功能描述: |
| LTC4260 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:UV, OV and Reverse Supply Protection Controller Low Operating Current: 125μA |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。