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参数资料
| 型号： | TPS2370D |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封装： | GREEN, PLASTIC, MS-012AA, SOIC-8 |
| 文件页数： | 16/17页 |
| 文件大小： | 426K |
| 代理商： | TPS2370D |
TPS2370
SLUS537C AUGUST 2002 REVISED MARCH 2004
www.ti.com
8
APPLICATION INFORMATION
POWER SOURCING EQUIPMENT POWER TO THE POWERED DEVICE
On completion of the detection and optional classification phases, the PSE ramps its output voltage above 42 V .
Once the UVLO threshold has been reached, the internal FET is turned on. At this point, the PD begins to
operate normally and it continues to operate normally as long as the input voltage remains above 30 V. For most
PDs, this input voltage is down-converted using an onboard dc-to-dc converter to generate the required voltages.
The TPS2370 is designed to apply the PSE output voltage of 36 V to 57 V across the input of the onboard
dc-to-dc converter. This is accomplished on the TPS2370 by turning on an internal pass FET located across the
power return.
PROGRAMMING THE INRUSH CURRENT
During the initial turnon of the pass FET, an inrush current is created from the charging of the capacitance at the
input of the dc-to-dc converter. According to the IEEE 802.3af specification, if the input capacitance is less than
180
F, the PSE limits the inrush current. If the input capacitance is greater than 180 F, the IEEE 802.3af
specification requires the PD to limit the inrush current to less than 400 mA.
In order to satisfy the IEEE 802.3af requirements, the TPS2370 has been designed for a typical current limit of
450 mA. This current limit setting satisfies the normal operation requirements as well as the inrush requirements
for a capacitive load of 180
F or less. If a larger load capacitor is desired, the TPS2370 has been designed with
a programmable inrush current limit feature. This feature allows the designer the option of using a capacitor
larger than 180
F. Note that the inrush current feature may also be used to lower voltage drops in the cabling
between the PSE and the PD during start-up.
The programmable inrush current limit has a range of 50 mA to 449 mA. The limit is set by connecting an
external resistor from ILIM (pin 1) to VEE (pin 4) of the TPS2370. Equation (1) shows the calculation for the
programmable inrush current limit.
I
INRUSH + 450 mA *
25 k
W
R
LIM
(1A)
where RLIM is a value between 63.5 k and 25 M.
USING EN_DC AS A SOFT-START OR A POWER-GOOD FUNCTION
The EN_DC pin is an output intended for use as a soft-start for a dc-to-dc converter. During the initial turnon of
the pass FET, an internal 80-
A current sink is enabled on the EN_DC pin. This internal current sink is removed
only after the load capacitance has been charged to within 1.5-V of the supply voltage. By connecting the
EN_DC output to the soft-start capacitor of a dc-to-dc converter, the internal current sink keeps the dc-to-dc
converter off during start-up. Once the voltage across the converter has reached within 1.5 V of full voltage, the
dc-to-dc converter is allowed to soft start.
For operation as a power-good output, the EN_DC requires an external pull-up resistor. A 1-M
resistor is
recommended. The EN_DC output also requires a clamp to limit the output voltage to within recommended
operating levels. A 5-V zener diode connected between EN_DC and RTN (pin 5 of the TPS2370) is
recommended. This configuration allows the EN_DC pin to act as an open-drain output with which many
designers are more familiar.
(2)
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS2370DG4 | 功能描述:热插拔功率分布 IEEE 802.3af Pwr Ifc Switch For PoE PD’s RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS2370DR | 功能描述:热插拔功率分布 IEEE 802.3af Pwr Ifc Switch For PoE PD’s RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS2370DRG4 | 功能描述:热插拔功率分布 IEEE 802.3af Pwr Ifc Switch For PoE PD’s RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| TPS2370EVM | 制造商:Texas Instruments 功能描述:TPS2370EVM - Bulk |
| TPS2370PW | 功能描述:热插拔功率分布 IEEE 802.3af Pwr Ifc Switch For PoE PD’s RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
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