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參數(shù)資料
| 型號： | LM25066APSQE |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 電源管理 |
| 英文描述： | POWER SUPPLY SUPPORT CKT, QCC24 |
| 封裝： | LLP-24 |
| 文件頁數(shù)： | 14/48頁 |
| 文件大?。?/td> | 1658K |
| 代理商： | LM25066APSQE |
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30146025
FIGURE 9. MOSFET Power Up Waveforms
TIMER CAPACITOR, C
T
The TIMER pin capacitor (C
T) sets the timing for the insertion
time delay, fault timeout period, and the restart timing of the
LM25066A.
A) Insertion Delay -
Upon applying the system voltage
(V
SYS) to the circuit, the external MOSFET (Q1) is held off
during the insertion time (t
1 in Figure 2) to allow ringing and
transients at V
SYS to settle. Since each backplane’s response
to a circuit card plug-in is unique, the worst case settling time
must be determined for each application. The insertion time
starts when VIN reaches the POR threshold, at which time the
internal 5.5 A current source charges C
T from 0V to 1.7V.
The required capacitor value is calculated from:
(7)
For example, if the desired insertion delay is 250 ms, C
T cal-
culates to 0.8 F. At the end of the insertion delay, C
T is
quickly discharged by a 1.9 mA current sink.
B) Fault Timeout Period -
During inrush current limiting or
upon detection of a fault condition where the current limit and/
or power limit circuits regulate the current through Q
1, the fault
timer current source (90 A) is switched on to charge C
T. The
Fault Timeout Period is the time required for the TIMER pin
voltage to reach 1.7V, at which time Q
1 is switched off. The
required capacitor value for the desired Fault Timeout Period
t
FAULT is calculated from:
(8)
For example, if the desired Fault Timeout Period is 15 ms,
C
T calculates to 0.8 F. CT is discharged by the 2.8 A current
sink at the end of the Fault Timeout Period. After the Fault
Timeout Period, if retry is disabled, the LM25066A latches the
GATE pin low until a power up sequence is initiated by exter-
nal circuitry. When the Fault Timeout Period of the LM25066A
expires, a restart sequence starts as described below
(Restart Timing). During consecutive cycles of the restart se-
quence, the fault timeout period is shorter than the initial fault
timeout period described above by approximately 20% since
the voltage at the TIMER pin starts ramping up from 0.3V
rather than ground.
Since the LM25066A normally operates in power limit and/or
current limit during a power up sequence, the Fault Timeout
Period MUST be longer than the time required for the output
voltage to reach its final value. See the Turn-On Time section.
C) Restart Timing -
For the LM25066A, after the Fault Time-
out Period described above, C
T is discharged by the 2.8 A
current sink to 1V. The TIMER pin then cycles through seven
additional charge/discharge cycles between 1V and 1.7V as
shown in Figure 4. The restart time ends when the TIMER pin
voltage reaches 0.3V during the final high-to-low ramp. The
restart time, after the Fault Timeout Period, is equal to:
(9)
= C
T x 2.3 x 10
6
(10)
For example, if C
T = 0.8 F, tRESTART = 2 seconds. At the end
of the restart time, Q
1 is switched on. If the fault is still present,
the fault timeout and restart sequence repeats. The on-time
duty cycle of Q
1 is approximately 0.67% in this mode.
UVLO, OVLO
By programming the UVLO and OVLO thresholds the
LM25066A enables the series pass device (Q
1) when the in-
put supply voltage (V
SYS) is within the desired operational
range. If V
SYS is below the UVLO threshold, or above the OV-
LO threshold, Q
1 is switched off, denying power to the load.
Hysteresis is provided for each threshold.
Option A:
The configuration shown in Figure 10 requires
three resistors (R1-R3) to set the thresholds.
21
www.national.com
LM25066A
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| LM25066APSQE/NOPB | 功能描述:熱插拔功率分布 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 |
| LM25066APSQX | 制造商:TI 制造商全稱:Texas Instruments 功能描述:System Power Management and Protection IC with PMBusa?￠ |
| LM25066APSQX/NOPB | 功能描述:熱插拔功率分布 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 |
| LM25066EVK/NOPB | 功能描述:電源管理IC開發(fā)工具 LM25066 EVAL BOARD 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 |
| LM25066IAPSQ/NOPB | 制造商:Texas Instruments 功能描述:IC PWR MGMT/PROT PMBUS 24WQFN 制造商:Texas Instruments 功能描述:System PWR Mgmt & Protection IC |
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