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參數(shù)資料
| 型號(hào)： | STHS4257A |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | IEEE 802.3af PoE Powered Device (PD) Interface Controller with Integrated Signature Resistor(集成識(shí)別電阻的IEEE802.3af PoE PD 接口控制器) |
| 中文描述： | IEEE 802.3af標(biāo)準(zhǔn)的PoE供電設(shè)備（PD）接口控制器，它集成簽名電阻（集成識(shí)別電阻的IEEE802.3af標(biāo)準(zhǔn)PoE電源接口控制器） |
| 文件頁(yè)數(shù)： | 13/18頁(yè) |
| 文件大?。?/td> | 173K |
| 代理商： | STHS4257A |
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STHS4257A, STHS4257A1, STHS4257L, STHS4257L1
Electrical parameters
13/18
I
LIMIT LOW
Input Current Limit, Low Level,
STHS4257x1
(inrush mode)
V
IN
= –48V, V
OUT
= –43V
(11)
,
(12)
100
140
180
mA
I
LIMIT
Input Current Limit,
STHS4257x
V
IN
= –48V, V
OUT
= –43V
(14)
300
350
400
mA
I
LIMIT WARM
Overtemperature Input Current
Limit,
STHS4257x
(14)
188
mA
T
OVERTEMP
Overtemperature Trip
Temperature,
STHS4257x
(14)
120
°C
T
SHUTDOWN
Thermal Shutdown Trip
Temperature
(11)
,
(13)
,
(14)
140
°C
1.
The STHS4257 family of PoE products operates with a negative supply voltage (with respect to the GND pin, unless
otherwise noted). Voltages in this data sheet are always referred to in terms of absolute magnitude, thus "maximum
negative voltage" means the most negative voltage and analogically "rising negative voltage" refers to a voltage that is
becoming more negative.
2.
The STHS4257 family of products is designed to work with two series diode drops caused by diode bridge that makes the
PD input polarity-insensitive. Parameter ranges specified in the Electrical Parameters Table are with respect to
STHS4257x/x1 pins and are designed to meet the IEEE 802.3af specifications when these diode drops are included. See
Figure 4 on page 8
.
3.
The STHS4257x/x1 devices include hysteresis in the UVLO voltages to avoid any start-up oscillation. As required by IEEE
802.3af, the STHS4257 family devices will power up from a voltage source with 20
Ω
series resistance on the first trial.
The Supply Current During Classification (I
IN CLASS
) does not include classification current programmed at pin 2. Total
supply current in classification mode will be I
IN CLASS
+ I
CLASS
(see also
Note 5
).
I
CLASS
is the measured current flowing through R
.
Δ
I
accuracy is with respect to the ideal current defined as
I
= 1.237/R
. The current accuracy specification does not include variations in R
resistance. The total
classification current seen by PSE also includes the quiescent current (I
IN
CLASS
). See
Figure 4 on page 8
.
Signature resistance is measured via the 2-point
Δ
V/
Δ
I method as defined by IEEE 802.3af standard. The STHS4257
device family signature resistance is offset from standard 25k
Ω
to account for the series diode bridge resistance. With two
series diodes, the total PD resistance will be between 23.75k
Ω
and 26.25k
Ω
which meets IEEE 802.3af specifications. The
minimum probe voltages measured at the STHS4257x/x1 pins are –1.5 and –2.5V. The maximum probe voltages are –8.5
and –9.5V.
To disable the 25k
Ω
signature, tie SIGDISA to GND (±0.1V) or hold SIGDISA high with respect to V
IN
. See
Figure 4 on
page 8
.
4.
5.
6.
7.
8.
V
is not used: To eliminate the current peak during the transition from inrush to normal operation mode, the
power MOSFET (between V
and V
- see
Figure 5 on page 9
) turns fully on only after the inrush current decreases by
10% from its initial value (i.e. when the output capacitor is fully charged).
9.
GND pin at the same potential as PWRGD pin to prevent ESD protection from impacting the measured results. To keep
PWRGD MOSFET off under this condition, maintain uninterrupted inrush current e.g. by applying 1V voltage between
V
OUT
and V
IN
pin. This will keep the device in inrush mode, thus preventing PWRGD from going active (on).
10. To significantly reduce I
and eliminate its impact on total current during detection and classification, the resistor
divider used to provide feedback on V
OUT
- V
IN
voltage is disconnected below the UVLO threshold.
11. The STHS4257x1 includes thermal protection. In the event of an overtemperature condition (T
is reached), the
STHS4257x1 will turn off the power MOSFET until the part cools below the overtemperature limit (T
). The
STHS4257x1 is also protected against thermal damage from incorrect classification probing by the PSE: If the
STHS4257x1 temperature exceeds the shutdown trip point (T
SHUTDOWN
), the classification load current is disabled.
12. The STHS4257x1 includes dual level input current limit. At turn-on, before output capacitor C2 is charged, the
STHS4257x1 current level is set to the low level. After the output capacitor C2 is charged, the STHS4257x1 switches to
high level current limit and remains there until the input voltage drops below the UVLO turn-off threshold.
13. The STHS4257 family devices include overtemperature protection that is intended to protect the device during momentary
overload conditions only. Continuous operation close to overtemperature limits may impair device reliability.
14. The STHS4257x includes smart thermal protection. In the event of an overtemperature condition, the STHS4257x will
reduce the input current limit by 50% to reduce the power dissipation in the package. If the part continues heating and
reaches the shutdown temperature (T
), the current is reduced to zero until the part cools below the
overtemperature limit (T
). The STHS4257x is also protected against thermal damage from incorrect classification
probing by the PSE: If the STHS4257x temperature exceeds the shutdown trip point (T
SHUTDOWN
), the classification load
current is disabled.
Table 5.
Electrical parameters (continued)
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
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| STHS4257A1 | IEEE 802.3af PoE Powered Device (PD) Interface Controller with Integrated Signature Resistor(集成識(shí)別電阻的IEEE802.3af PoE PD 接口控制器) |
| STHS4257L | IEEE 802.3af PoE Powered Device (PD) Interface Controller with Integrated Signature Resistor(集成識(shí)別電阻的IEEE802.3af PoE PD 接口控制器) |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| STHS4257A1 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:IEEE 802.3af PoE Powered Device (PD) interface controller with integrated signature resistor |
| STHS4257A1M6E | 功能描述:熱插拔功率分布 ADV Analog RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| STHS4257A1M6F | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 STHS4257A STHS4257A1 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| STHS4257L | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:IEEE 802.3af PoE Powered Device (PD) interface controller with integrated signature resistor |
| STHS4257L1 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:IEEE 802.3af PoE Powered Device (PD) interface controller with integrated signature resistor |
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