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| 型号： | TPS2412PWG4 |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDSO8 |
| 封装： | GREEN, PLASTIC, TSSOP-8 |
| 文件页数： | 5/25页 |
| 文件大小： | 1052K |
| 代理商： | TPS2412PWG4 |
TPS2412 REGULATION-LOOP STABILITY
MOSFET SELECTION AND R(RSET)
-470.02
R(RSET)
V
- 0.00314
(OFF)
÷
=
÷
è
(2)
www.ti.com.......................................................................................................................................... SLVS728B – JANUARY 2007 – REVISED SEPTEMBER 2008
The TPS2412 uses an internal linear error amplifier to keep the external MOSFET from saturating at light load.
This feature has the benefits of setting a turn-off above 0 V, providing a soft turn-off for slowly decaying input
voltages, and helps droop-sharing redundancy at light load.
Although the control loop has been designed to accommodate a wide range of applications, there are a few
guidelines to be followed to assure stability.
Select a MOSFET C
(ISS) of 1 nF or greater
Use low ESR bulk capacitors on the output C terminal, typically greater than 100F with less than 50 m
ESR
Maintain some minimum operational load (e.g. 10 mA or more)
Symptoms of stability issues include V(AC) undershoot and possible fast turn-off on large-transient recovery, and
a worst-case situation where the gate continually cycles on and off. These conditions are solved by following the
rules above. Loop stability should not be confused with tripping the fast comparator due to V(AC) tripping the gate
off.
Although not common, a condition may arise where the dc/dc converter transient response may cause the GATE
to cycle on and off at light load. The converter experiences a load spike when GATE transitions from OFF to ON
because the ORed bus capacitor voltage charges abruptly by as much as a diode drop. The load spike may
cause the supply output to droop and overshoot, which can result in the ORed capacitor peak charging to the
overshoot voltage. When the supply output settles to its regulated value, the ORed bus may be higher than the
source, causing the TPS2412/13 to turn the GATE off. While this may not actually cause a problem, its
occurrence may be mitigated by control of the power supply transient characteristic and increasing its output
capacitance while increasing the ORed load to capacitance ratio. Adjusting the TPS2412/13 turn-off threshold to
desensitize the redundant ORing device may help as well. Careful attention to layout and charge-pump noise
around the TPS2412/13 helps with noise margin.
The linear gate driver has a pull-up current of 290
A and pull-down current of 3 mA typical.
MOSFET selection criteria include voltage rating, voltage drop, power dissipation, size, and cost. The voltage
rating consists of both the ability to withstand the rail voltage with expected transients, and the gate breakdown
voltage. The MOSFET gate rating should be the minimum of 12 V, or the controlled rail voltage. Typically this
requires a ±20-V GATE voltage rating.
While rDS(on) is often chosen with the power dissipation, voltage drop, size and cost in mind, there are several
other factors to be concerned with in ORing applications. When using the TPS2412, the minimum voltage across
the device is 10 mV. A device that would have a lower voltage drop at full-load would be overspecified. When
using a TPS2413 or TPS2412 with RSET programmed to a negative voltage, the permitted static reverse current
is equal to the turn-off threshold divided by the rDS(on). While this current may actually be desirable in some
systems, the amount may be controlled by selection of rDS(on) and RSET. The practical range of rDS(on) for a
single MOSFET runs from the low milliohms to 40 m
for a single MOSFET.
MOSFETs may be paralleled for lower voltage drop (power loss) at high current. For TPS2412 operation, one
should plan for only one of the MOSFETs to carry current until the 10 mV regulation point is exceeded and the
loop forces GATE fully ON. TPS2413 operation does not rely on linear range operation, so the MOSFETs are all
ON or OFF together except for short transitional times. Beyond the control issues, current sharing depends on
the resistance match including both the rDS(on) and the connection resistance.
The TPS2412 may be used without a resistor on RSET. In this case, the turnoff V(AC) threshold is about 3 mV.
The TPS2413 may only be operated without an RSET programming resistor if the loading provides a higher
V(AC). A larger negative turnoff threshold reduces sensitivity to false tripping due to noise on the bus, but permits
larger static reverse current. Installing a resistor from RSET to ground creates a negative shift in the fast turn-off
threshold per Equation 2.
Copyright 2007–2008, Texas Instruments Incorporated
13
Product Folder Link(s): TPS2412 TPS2413
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| TPS2412PWR | 功能描述:热插拔功率分布 N+1 OR-ing Pwr Rail Cntrlr 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 |
| TPS2412PWRG4 | 功能描述:热插拔功率分布 N+1 and OR-ing Pwr Rail Controller 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 |
| TPS2413D | 功能描述:热插拔功率分布 O-ring controller 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 |
| TPS2413DG4 | 功能描述:热插拔功率分布 O-ring Cntrlr 8pin 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 |
| TPS2413DR | 功能描述:热插拔功率分布 O-ring controller 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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