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PDF STHS4257A1 Data sheet ( Hoja de datos )
| Número de pieza | STHS4257A1 | |
| Descripción | IEEE 802.3af PoE Powered Device (PD) interface controller | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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STHS4257A, STHS4257A1
STHS4257L, STHS4257L1
IEEE 802.3af PoE Powered Device (PD)
interface controller with integrated signature resistor
Features
■ IEEE 802.3af-compliant interface for Powered
Devices (PDs)
■ Integrated 100V, 450mA power MOSFET low
side switch
8
1
SO8 (M)
■ Inrush current limit
■ Normal operation current limit
■ Integrated 25kΩ signature resistor
)■ Signature disable (STHS4257A1/L1)
t(s■ Resistor-programmable classification current
c(Class 0-4)
du■ Power Good output, open drain
ro■ Undervoltage Lockout (UVLO)
P■ Thermal overload protection (two-step for the
teSTHS4257A/L)
le■ Latch (L) or auto-retry (A) after repetitive
sothermal overload
b■ Industrial temperature range: –40 to +85°C
- O■ SO8 and DFN8 (3mm x 3mm) packages
)■ RoHS compliant
DFN8 3mm x 3mm (DB)
Applications
■ Voice over IP (VoIP) phones
■ Web cameras
■ WLAN access points
■ Internet appliances
■ POS terminals
■ RFID readers
duct(sTable 1. Device options
lete ProOrder code
Signature
disable
UVLO
threshold,
rising (V)
soSTHS4257A
ObSTHS4257A1
✔
39.2
36.0
UVLO
threshold,
falling (V)
30.5
30.5
Protection
mode
Thermal
overload
protection
Inrush
current limit
(mA, typ)
Normal
operation
current limit
(mA, typ)
Auto
2 steps
350/188 (1)
Auto
1 step
140
375
STHS4257L
39.2
30.5
Latch
2 steps
350/188 (1)
STHS4257L1
✔
36.0
30.5
Latch
1 step
140
375
1. Current limit is common for both modes and gets reduced only in case of thermal overload. See Table 5: Electrical parameters.
July 2007
Rev 4
1/18
www.st.com
1
1 page  
STHS4257A, STHS4257A1, STHS4257L, STHS4257L1
1 Summary description
Summary description
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The STHS4257 is an IEEE802.3af-compliant family of interface controllers for Power over
Ethernet (PoE) Powered Device (PD) applications. The devices consist of two main
sections:
● The IEEE802.3af interface to the PoE powered RJ-45 wall socket, and
● the Hot Swap Controller (HSC) functions required to protect the PD during insertion,
operation, and withdrawal from the RJ-45 socket.
These devices have an integrated high voltage power MOSFET (low-side switch) with low
RON and the capability to accept transients as high as 100V. Since the pins (such as GND
and VIN) which interface to the RJ-45 socket can routinely see high peak voltages in excess
of 100V, it is strongly recommended that board designers protect the PD device with a
transient voltage suppressor, such as the SMAJ58A (available from STMicroelectronics),
connected between the GND and VIN pins (see Figure 4 on page 8).
The IEEE802.3af-compliant interface includes the basic PD detection and Classification
functions, whereas the ‘Hot Swap’ functions include other basic features, such as Inrush
)Current Limiting, Undervoltage Lockout (UVLO), and Thermal Overload Protection. All of the
t(sdevices include an open drain Power Good (PWRGD) signal to indicate normal steady
coperation (see Figure 1 on page 6 and Table 2 on page 6). The STHS4257 family also
uincorporates a 1.5V voltage offset (two series diodes) to accommodate the input diode
dbridge used to make the PD polarity insensitive.
ProThe STHS4257A1/L1 includes a dual level current limit circuit. This allows the
STHS4257A1/L1 to interface with legacy Power over Ethernet (LAN) systems while
temaintaining compatibility with the current IEEE 802.3af specification.
oleEach of the two basic part types, the STHS4257A/L and the STHS4257A1/L1, is available
seither with Latched Operation (L) Mode or with Automatic Retry (A) Mode after fault
Obsolete Product(s) - Obconditions. For product options overview see Table 1 on page 1.
5/18
5 Page 
STHS4257A, STHS4257A1, STHS4257L, STHS4257L1
Absolute maximum ratings
2
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Absolute maximum ratings
Stressing the device above the rating listed in the Table 4: Absolute maximum ratings may
cause permanent damage to the device. These are stress ratings only and operation of the
device at these or any other conditions above those indicated in the Operating sections of
this specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability. Refer also to the STMicroelectronics SURE
Program and other relevant quality documents.
Table 4. Absolute maximum ratings
Symbol
Parameter
Value
Unit
VIN Input/supply voltage (1)
+0.3 to –100
V
VOUT
Voltage on VOUT pin
VIN +100 to VIN –0.3
V
VSIGDISA, VPWRGD Voltage on the respective pins
VIN +90 to VIN –0.3
V
VRCLASS
Voltage on RCLASS pin
VIN +7 to VIN –0.3
V
IPWRGD
)IRCLASS
t(sTA
ucTSTG
rodTSLD
Power Good output current
RCLASS pin current
Operating ambient temperature range
Storage temperature
Lead solder temperature for 10 seconds,
lead-free lead finish (2)
10
100
–40 to 85
–55 to 150
260
mA
mA
°C
°C
°C
te P1. With respect to the GND pin.
Obsolete Product(s) - Obsole2. Reflow at peak temperature of 260°C (total thermal budget not to exceed 245°C for more than 30 seconds).
11/18
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| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet STHS4257A1.PDF ] | |
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