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參數(shù)資料
| 型號(hào)： | ISL6721AV |
| 廠商： | INTERSIL CORP |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | 1024 x 9 x 2 Asynchronous Bidirectional FIFO Memory 64-TQFP 0 to 70 |
| 中文描述： | 1 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 4.40 MM, PLASTIC, MO-153AB, TSSOP-16 |
| 文件頁(yè)數(shù)： | 10/20頁(yè) |
| 文件大?。?/td> | 481K |
| 代理商： | ISL6721AV |
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10
results in a control loop that behaves more as a voltage
mode controller than as current mode controller.
The minimum amount of capacitance to place at the SLOPE
pin is:
where ton is the On time and Vslope is the amount of voltage
to be added as slope compensation to the current feedback
signal. In general, the amount of slope compensation added
is 2 to 3 times the minimum required.
Example:
Assume the inductor current signal presented at the ISENSE
pin decreases 125mV during the Off period, and:
Switching Frequency, Fsw = 250kHz
Duty Cycle, D = 60%
ton = D/Fsw = 0.6/250E3 = 2.4
μ
S
toff = (1 - D)/Fsw = 1.6
μ
S
Determine the downslope:
Downslope = 0.125V/1.6
μ
S = 78mV/
μ
S. Now determine the
amount of voltage that must be added to the current sense
signal by the end of the On time.
1
2
Therefore
An appropriate slope compensation capacitance for this
example would be 1/2 to 1/3 the calculated value, or
between 68 and 33pF.
Over and Under Voltage Monitor
The OV and UV signals are inputs to a window comparator
used to monitor the input voltage level to the converter. If the
voltage falls outside of the user designated operating range,
a shutdown fault occurs. For OV faults, the supply current,
I
CC
, is reduced to 200
μ
A for ~ 295ms at which time recovery
is attempted. If the fault is cleared, a soft start cycle begins.
Otherwise another shutdown cycle occurs. A UV condition
also results in a shutdown fault, but the device does not
enter the low power mode and no restart delay occurs when
the fault clears.
A resistor divider between Vin and LGND to each input
determines the operational thresholds. The UV threshold
has a fixed hysteresis of 75mV nominal.
Over Current Operation
The over current threshold level is set by the voltage applied
at the ISET pin. Setting the over current level may be
accomplished by using a resistor divider network from VREF
to LGND. The ISET threshold should be set at a level that
corresponds to the desired peak output inductor current plus
the additive effects of slope compensation.
Over current delayed shutdown is enabled once the soft start
cycle is complete. If an over current condition is detected,
the soft start charging current source is disabled and the
discharging current source is enabled. The soft start
capacitor is discharged at a rate of 40
μ
A. At the same time a
50
μ
S retriggerable one-shot timer is activated. It remains
active for 50
μ
S after the over current condition stops. The
soft start discharge cycle cannot be reset until the one-shot
timer becomes inactive. If the soft start capacitor discharges
by more then 0.125V to 4.375V, the output is disabled and
the soft start capacitor is discharged. The output remains
disabled and I
CC
drops to 200
μ
A for approximately 295ms.
A new soft start cycle is then initiated. The shutdown and
restart behavior of the OC protection is often referred to as
hic-cup operation due to its repetitive start-up and shutdown
characteristic.
If the over current condition ceases at least 50
μ
S prior to the
soft start voltage reaching 4.375V, the soft start charging and
discharging currents revert to normal operation and the soft
start voltage is allowed to recover.
Hic-cup OC protection may be defeated by setting ISET to a
voltage that exceeds the Error Amplifier current control
voltage, or about 1.5V.
Leading Edge Blanking
The initial 100ns of the current feedback signal input at
ISENSE is removed by the leading edge blanking circuitry.
The blanking period begins when the GATE output leading
edge exceeds 3.0V. Leading edge blanking prevents current
spikes from parasitic elements in the power supply from
causing false trips of the PWM comparator and the over
current comparator.
Fault Conditions
A Fault condition occurs if VREF falls below 4.65V, the OV
input exceeds 2.50V, the UV input falls below 1.45V, or the
junction temperature of the die exceeds ~130
o
C. When a
Fault is detected the GATE output is disabled and the soft
start capacitor is quickly discharged. When the Fault
TIME
I
Downslope
DOWNSLOPE
Current Sense Signal
CURRENT SENSE SIGNAL
FIGURE 5.
I
Cslope
4.24
6
–
×
10
--------------------
=
F
(EQ. 6)
Vslope
--
0.078
2.4
94mV
=
=
(EQ. 7)
Cslope min
)
4.24
6
–
×
10
------------10
6
–
110pF
≈
=
(EQ. 8)
ISL6721
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISL6721AV-T | 功能描述:電流型 PWM 控制器 FLEXIBLE SINGLE END CUR MODE PWM RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| ISL6721AVZ | 功能描述:電流型 PWM 控制器 FLEX SNG ENDED CUR MODE PWM CONTRLR RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| ISL6721AVZ-T | 功能描述:IC REG CTRLR PWM CM 16-TSSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 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:275kHz 占空比:50% 電源電壓:18 V ~ 110 V 降壓:無(wú) 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:是 工作溫度:-40°C ~ 85°C 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) |
| ISL6721EVAL1 | 功能描述:EVALUATION BOARD ISL6721 RoHS:否 類(lèi)別:RF/IF 和 RFID >> RF 評(píng)估和開(kāi)發(fā)套件，板 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類(lèi)型:GPS 接收器 頻率:1575MHz 適用于相關(guān)產(chǎn)品:- 已供物品:模塊 其它名稱(chēng):SER3796 |
| ISL6721EVAL3Z | 功能描述:EVAL BOARD 3 FOR ISL6721 RoHS:是 類(lèi)別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - DC/DC 與 AC/DC（離線(xiàn)）SMPS 系列:* 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:True Shutdown™ 主要目的:DC/DC，步升 輸出及類(lèi)型:1，非隔離 功率 - 輸出:- 輸出電壓:- 電流 - 輸出:1A 輸入電壓:2.5 V ~ 5.5 V 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):升壓 頻率 - 開(kāi)關(guān):3MHz 板類(lèi)型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
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