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參數(shù)資料
| 型號： | ISL6721AV |
| 廠商： | INTERSIL CORP |
| 元件分類： | 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 |
| 文件頁數(shù)： | 9/20頁 |
| 文件大小： | 481K |
| 代理商： | ISL6721AV |
9
V
CC
to LGND with a ceramic capacitor as close to the V
CC
and LGND pins as possible.
The total supply current (I
C
plus I
CC
) will be higher,
depending on the load applied to GATE. Total current is the
sum of the quiescent current and the average gate current.
Knowing the operating frequency, Fsw, and the MOSFET
gate charge, Qg, the average GATE output current can be
calculated from:
VREF -
The 5.00V reference voltage output. Bypass to
LGND with a 0.01
μ
F or larger capacitor to filter this output as
needed. Using capacitance less than this value may result in
unstable operation.
SS -
Connect the soft start capacitor between this pin and
LGND to control the duration of soft start. The value of the
capacitor determines both the rate of increase of the duty
cycle during start up, and also controls the over current
shutdown delay.
ISET -
A DC voltage between 0.35 and 1.2V applied to this
input sets the pulse-by-pulse over current threshold. When
over current inception occurs, the SS capacitor begins to
discharge and starts the over current delayed shutdown
cycle.
Functional Description
Features
The ISL6721 current mode PWMs make an ideal choice for
low-cost flyback and forward topology applications requiring
enhanced control and supervisory capability. With adjustable
over and under voltage thresholds, over current threshold,
and hic-cup delay, a highly flexible design with minimal
external components is possible. Other features include
peak current mode control, adjustable soft-start, slope
compensation, adjustable oscillator frequency, and a bi-
directional synchronization clock input.
Oscillator
The ISL6721 have a sawtooth oscillator with a
programmable frequency range to 1MHz, which can be
programmed with a resistor and capacitor on the RTCT pin.
(Please refer to Fig. 4
for the resistance and capacitance
required for a given frequency.)
Implementing Synchronization
The oscillator can be synchronized to an external clock
applied at the SYNC pin or by connecting the SYNC pins of
multiple ICs together. If an external master clock signal is
used, it must be at least 65% of the free running frequency of
the oscillator for proper synchronization. The external master
clock signal should have a pulse width greater than 20ns. If
no master clock is used, the first device to assert SYNC
assumes control of the SYNC signal. An external SYNC
pulse is ignored if it occurs during the first 1/3 of the
switching cycle.
During normal operation the RTCT voltage charges from 1.5
to 3.0V and back during each cycle. Clock and SYNC signals
are generated when the 3.0V threshold is reached. If an
external clock signal is detected during the latter 2/3 of the
charging cycle, the oscillator switches to external
synchronization mode and relies upon the external SYNC
signal to terminate the oscillator cycle. The generation of a
SYNC signal is inhibited in this mode. If the RTCT voltage
exceeds 4.0V (i.e. no external SYNC signal terminates the
cycle), the oscillator reverts to the internal clock mode and a
SYNC signal is generated.
Soft-Start Operation
The ISL6721 features soft-start using an external capacitor
in conjunction with an internal current source. Soft-start is
used to reduce voltage stresses and surge currents during
start up.
Upon start up, the soft start circuitry clamps the error
amplifier output (COMP pin) to a value proportional to the
soft start voltage. The error amplifier output rises as the soft
start capacitor voltage rises. This has the effect of increasing
the output pulse width from zero to the steady state
operating duty cycle during the soft start period. When the
soft start voltage exceeds the error amplifier voltage, soft
start is completed. Soft start forces a controlled output
voltage rise. Soft-start occurs during start-up and after
recovery from a fault condition or over current shutdown. The
soft start voltage is clamped to 4.5V.
Gate Drive
The ISL6721 is capable of sourcing and sinking 1A peak
current. Separate collector supply (V
C
) and power ground
(PGnd) pins help isolate the IC’s analog circuitry from the
high power gate drive noise. To limit the peak current
through the IC, an external resistor may be placed between
the totem-pole output of the IC (GATE pin) and the gate of
the MOSFET. This small series resistor also damps any
oscillations caused by the resonant tank of the parasitic
inductances in the traces of the board and the FET’s input
capacitance.
Slope Compensation
For applications where the maximum duty cycle is less than
50%, slope compensation may be used to improve noise
immunity, particularly at lighter loads. The amount of slope
compensation required for noise immunity is determined
empirically, but is generally about 10% of the full scale
current feedback signal. For applications where the duty
cycle is greater than 50%, slope compensation is required to
prevent instability. Slope compensation is a technique in
which the current feedback signal is modified by adding
additional slope to it. The minimum amount of slope
compensation required corresponds to 1/2 the inductor
downslope. However, adding excessive slope compensation
(EQ. 5)
Igate
Qg
Fsw
=
A
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 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 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 類別:RF/IF 和 RFID >> RF 評估和開發(fā)套件，板 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類型: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:SER3796 |
| ISL6721EVAL3Z | 功能描述:EVAL BOARD 3 FOR ISL6721 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - DC/DC 與 AC/DC（離線）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 - 開關(guān):3MHz 板類型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
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