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參數(shù)資料
| 型號(hào)： | LM27241 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Synchronous Buck Regulator Controller for Mobile Systems |
| 中文描述： | 同步降壓穩(wěn)壓控制器，用于移動(dòng)通信系統(tǒng) |
| 文件頁數(shù)： | 14/27頁 |
| 文件大小： | 1336K |
| 代理商： | LM27241 |
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Operation Descriptions
(Continued)
The recovery procedure from a VIN Power-off is the same as
for any fault condition.
VDD POWER-OFF (UVLO)
Whenever VDD starts to fall, and drops below about 3.5V,
LDRV goes high immediately, ‘Power Not Good’ is signaled
and in effect a fault condition (in this case an Under-voltage
lockout) is asserted. Recovery from a fault is discussed in
the "Fault and Recovery" section.
OVER-VOLTAGE PROTECTION
If the voltage on the FB pin exceeds 113% of 0.60V, a Power
Not Good signal is asserted. If the voltage on the FB pin
exceeds 130% of 0.60V, a fault condition is declared, and the
LDRV goes high. If the fault persists, the low-side FET will
stay on and the high-side FET will not turn back on until the
FB pin falls within the power good window, and the Enable
pin is toggled.
CURRENT LIMIT AND PROTECTION
Output current limiting is achieved by sensing the negative
Vds drop across the low-side FET when the FET is turned
ON. The Current Limit Comparator (see Block Diagram)
monitors the voltage at the ILIM pin with 62μA (typical value)
of current being sourced from the pin. The 62μAsource flows
through an external resistor connected between ILIM and
the drain of the low-side FET. The voltage drop across the
ILIM resistor is compared with the drop across the low-side
FET and the current limit comparator trips when the two are
of the same magnitude. This determines the threshold of
current limiting. For example, if excessive inductor current
causes the voltage across the low-side FET to exceed the
voltage drop across the ILIM resistor, the ILIM pin will go
negative (with respect to ground) and trip the comparator.
The comparator then sets a latch that prevents the high-side
FET from turning ON during the next PWM clock cycle. The
high-side FET will resume switching only if the current limit
comparator was not tripped in the previous switching cycle.
Additionally, the Soft-start capacitor at the SS pin is dis-
charged with a 115μA current source when an overcurrent
event is in progress. The purpose of discharging the Soft-
start capacitor during an overcurrent event is to eventually
allow the voltage on the SS pin to fall low enough to cause
additional duty cycle limiting.
R
LIMIT
= (R
DS_ON
x I
LIMIT
/ 62 μA)
20120115
CH1: PGOOD, CH2: VIN, CH3: LDRV, CH4: Vo
Output 1V
@
0.02A, VIN = 9.75V, FPWM, L = 10μH, f = 300kHz, C
OUT
=
660μF
FIGURE 8. VIN Removal in FPWM Mode
20120116
CH1: PGOOD, CH2: VIN, CH3: LDRV, CH4: Vo
Output 1V
@
0.02A, VIN = 9.75V, SKIP, L = 10μH, f = 300kHz, C
OUT
=
660μF
FIGURE 9. VIN Removal in SKIP Mode
L
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| LM27241MTCX | Synchronous Buck Regulator Controller for Mobile Systems |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM27241MTC | 制造商:Texas Instruments 功能描述:PWM CONTROLLER SMD 27241 TSSOP20 |
| LM27241MTC/NOPB | 功能描述:IC REG CTRLR BUCK PWM VM 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LM27241MTCX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Synchronous Buck Regulator Controller for Mobile Systems |
| LM27241MTCX/NOPB | 功能描述:IC REG CTRLR BUCK PWM VM 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:100% 電源電壓:8.2 V ~ 30 V 降壓:無 升壓:無 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁面:1316 (CN2011-ZH PDF) |
| LM27243A E WAF | 制造商:Texas Instruments 功能描述: |
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