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參數(shù)資料
| 型號： | ISL6444 |
| 廠商： | Intersil Corporation |
| 英文描述： | Dual PWM Controller with DDR Memory Option for Gateway Applications(帶DDR存儲器選項(xiàng)的網(wǎng)關(guān)專用雙PWM控制器) |
| 中文描述： | 雙PWM控制器的DDR網(wǎng)關(guān)應(yīng)用（帶的DDR存儲器選項(xiàng)的網(wǎng)關(guān)專用雙脈寬調(diào)制控制器內(nèi)存選項(xiàng)） |
| 文件頁數(shù)： | 9/19頁 |
| 文件大?。?/td> | 372K |
| 代理商： | ISL6444 |
9
FN9069.3
April 12, 2007
synchronous MOSFET compared to a Shottky diode. In
contrast, continuous-conduction operation in load currents
lower than the inductor critical value results in lower
efficiency. In this case, during a fraction of a switching cycle,
the direction of the inductor current changes to the opposite
actively discharging the output filter capacitor.
To maintain the output voltage in regulation, the discharged
energy should be restored during the consequent cycle of
operation by the cost of increased circulating current and
losses associated with it.
The critical value of the inductor current can be estimated by
the following expression.
To improve converter efficiency in loads lower than critical,
the switch-over to variable frequency hysteretic operation
with diode emulation is implemented into the PWM scheme.
The switch-over is provided automatically by the mode
control circuit that constantly monitors the inductor current
and alters the way the PWM signal is generated.
The voltage across the synchronous MOSFET at the
moment of time just before the upper-MOSFET turns on is
monitored for purposes of mode change. When the
converter operates in currents higher than critical, this
voltage is always positive as shown in Figure 3 and 4. In
currents lower than critical, the voltage is always negative.
The mode control circuit uses a sign of voltage across the
synchronous devices to determine if the load current is
higher or lower than the critical value.
To prevent chatter between operating modes, the circuit
looks for eight sequential matching sign signals before it
makes its decision to perform a mode change. The same
algorithm is true for both CCM-hysteretic and hysteretic-
CCM transitions.
Hysteretic Operation
When the critical inductor current is detected, the converter
enters hysteretic mode. The PWM comparator and the error
amplifier that provided control in the CCM mode are inhibited
and the hysteretic comparator is now activated. A change is
also made to the gate logic. In hysteretic mode the
synchronous rectifier MOSFET is controlled in diode
emulation mode, hence conduction in the second quadrant
is prohibited.
The hysteretic comparator initiates the PWM signal when the
output voltage gets below the lower threshold and
terminates the PWM signal when the output voltage rises
over the upper threshold. A spread or hysteresis between
these two thresholds determines the switching frequency
and the peak value of the inductor current. A transition to a
constant frequency CCM mode will happen when the load
current gets to a level higher than the critical:
Where,
Δ
V
hys
= 15mV, is a hysteretic comparator window,
ESR is the equivalent series resistance of the output
capacitor.
Because of different control mechanisms, the value of the
load current where transition into CCM operation takes place
FIGURE 2. OUTPUT VOLTAGE PROGRAM
R2
R1
UGATE
LGATE
ISL6444
L1
Q1
Q2
C1
VOUT
VSEN
Vin
R
CS
ISEN
OCSET
R
OC
Cz
I
HYS
V
SW
V
–
(
)
V
IN
O
--------------------------------------------------
=
(EQ. 4)
FIGURE 3. CCM -- HYSTERETIC TRANSITION
PWM
Hysteretic
1 2 3 4 5 6 7 8
VOUT
IIND
PHASE
COMP
OPERATION
MODE
t
t
t
t
FIGURE 4. HYSTERETIC -- CCM TRANSITION
PWM
Hysteretic
1 2 3 4 5
6 7 8
VOUT
IIND
PHASE
COMP
OPERATION
MODE
t
t
t
t
I
CCM
Δ
V
---------------------
≈
(EQ. 5)
ISL6444
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| ISL6444CA | 功能描述:電流型 PWM 控制器 Dual with DDR Memory 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 |
| ISL6444CA-T | 功能描述:IC CONTROLLER DDR 28-QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,000 系列:- 應(yīng)用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應(yīng)商設(shè)備封裝:42-WLP 包裝:帶卷 (TR) |
| ISL6444CAZ | 功能描述:IC CONTROLLER DDR 28-QSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| ISL6444CAZT | 制造商:Intersil Corporation 功能描述: |
| ISL6444CAZ-T | 功能描述:IC CONTROLLER DDR 28-QSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
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