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參數(shù)資料
| 型號： | TPS2376DDAR-H |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 電源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封裝： | GREEN, PLASTIC, POWER PAD, SOIC-8 |
| 文件頁數(shù)： | 6/23頁 |
| 文件大?。?/td> | 640K |
| 代理商： | TPS2376DDAR-H |
www.ti.com
ESD
EXTERNAL COMPONENTS
Detection Resistor and UVLO Divider
Magnetics
Input Diodes or Diode Bridges
Input Capacitor
SLVS646A – SEPTEMBER 2006 – REVISED SEPTEMBER 2006
APPLICATION INFORMATION (continued)
The TPS2376-H has been tested using the surge of EN61000-4-2 in evaluation circuit similar to Figure 1. The
levels used were 8-kV contact discharge and 15-kV air discharge. Surges were applied between the RJ-45 and
the outputs, and between an auxiliary power input jack and the dc outputs. No failures were observed.
ESD requirements for a unit that incorporates the TPS2376-H have much broader scope and operational
implications than those used in TI’s testing. Unit level requirements should not be confused with EVM testing
that only validated the TPS2376-H.
The UVLO divider shown in Figure 1 is suitable where elimination of the detection resistor is desirable and the
IEEE 802.3af compatible turn on is desired. The upper resistor dissipates about 116 mW at 55.5 V (57 V minus
1.5 V for an input diode bridge) at the maximum input, and supports 52 V. An 0805 size resistor is
recommended for this resistor while an 0603 size resistor is suitable for the lower resistor.
Improved efficiency is obtained by using a detection resistor along with high-value UVLO resistors. The
maximum UVLO divider resistance may be determined by considering the effect of the UVLO pin leakage
current. The error is equal to the leakage current times the parallel resistance of the divider resistors. This may
be simplified for the 39.5 V turn-on case to the leakage current times the lower divider resistance. The maximum
resistance is the error voltage divided by the leakage current. For a 0.5% error, the maximum resistance is
(0.005 * 2.49 V) / 1
A, or approximately 12.4 k. A possible divider for a turn-on voltage of 39.5 V is 178 k /
12.1 k
resulting in a turn-on voltage of 39.1 V. A suitable value for R
DET is 28.7 k, yielding a detection
resistance of 24.93 k
. The operating power loss at 55.5 V is 16 mW.
The input diode bridge's incremental resistance can be hundreds of ohms at the low currents seen at 2.7 V on
the PI. The bridge resistance is in series with R(DET) and increases the total resistance seen by the PSE. This
varies with the type of diode selected by the designer, and it is not usually specified on the diode data sheet.
The value of R(DET) may be adjusted downwards to accommodate a particular diode type. The non-linear
resistance of Figure 3 at low currents is the result of the diodes.
A high-power PoE system places additional burden on power extraction from data pairs. Data transmission
properties must be maintained while carrying higher current and withstanding higher difference current between
the conductors in a pair. This difference current is the result of unbalanced resistances between the conductors
of a pair (see IEEE 802.3af annex 33E).
Either a higher current center-tapped transformer as shown in Figure 1, or the addition of a center-tapped
inductor, can be implemented. Proper termination is required around the transformer to provide correct
impedance matching and to avoid radiated and conducted emissions.
The IEEE 802.3af requires the PD to accept power on either set of input pairs in either polarity. This requirement
is satisfied by using two full-wave input bridge rectifiers as shown in Figure 1. The full configuration may not be
required when a custom high-power system is implemented. Silicon p-n diodes with a 1-A or 1.5-A rating and a
minimum breakdown of 100 V are recommended, however Schottky diodes will yield a somewhat lower power
loss. Diodes exhibit large dynamic resistance under low-current operating conditions such as in detection. The
diodes should be tested for their behavior under this condition. The total forward drops must be less than 1.5 V
at 500
A and at the lowest operating temperature.
The IEEE 802.3af requires a PD input capacitance between 0.05
F and 0.12 F during detection. This
capacitor should be located directly adjacent to the TPS2376-H as shown in Figure 1. A 100-V, 10%, X7R
ceramic capacitor meets the specification over a wide temperature range.
14
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| TPS2376DDAR-HG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Hi Pwr PD CONTROLLER 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 |
| TPS2376DG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler 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 |
| TPS2376DR | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler 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 |
| TPS2376DRG4 | 功能描述:熱插拔功率分布 IEEE 802.3af PoE Pwr Device Cntrler 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 |
| TPS2376HEVM | 功能描述:電源管理IC開發(fā)工具 TPS2376H Evaluation Module RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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