參數(shù)資料
型號(hào)： ISL6225CA-T
廠商： INTERSIL CORP
元件分類： 穩(wěn)壓器
英文描述： Dual Mobile-Friendly PWM Controller with DDR Memory Option
中文描述： DUAL SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO28
封裝： PLASTIC, SSOP-28
文件頁(yè)數(shù)： 9/19頁(yè)
文件大?。?/td> 522K
代理商： ISL6225CA-T
9
FN9049.7
December 28, 2004
Automatic Operation Mode Control
In nominal currents the synchronous buck converter
operates in continuous-conduction constant-frequency
mode. This mode of operation achieves higher efficiency
due to the substantially lower voltage drop across the
synchronous MOSFET compared to a Schottky diode.
In contrast, continuous-conduction operation with 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 at 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 at currents higher than critical, this
voltage is always negative. In currents lower than critical, the
voltage is always positive. 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 contiguous signals of the same polarity before
it makes the 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.
FIGURE 4. OUTPUT VOLTAGE PROGRAM
R2
R1
UGATE
LGATE
ISL6225
L1
Q1
Q2
C1
VOUT
VSEN
VIN
R
CS
ISEN
OCSET
R
OC
Cz
IHYS
–
(
)
-----------------------------------------------------
=
FIGURE 5. CCM - HYSTERETIC TRANSITION
PWM
HYSTERETIC
1 2 3 4 5 6 7 8
VOUT
IIND
PHASE
COMP
OPERATION
OF
t
t
t
t
FIGURE 6. HYSTERETIC - CCM TRANSITION
PWM
HYSTERETIC
1 2 3 4 5
6 7 8
VOUT
IIND
PHASE
COMP
OPERATION
OF
t
t
t
t
ISL6225
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ISL6225CAZ 功能描述:電流型 PWM 控制器 DL SWITCHER W/DRR OPTION 30V CS80 FSC 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
ISL6225CAZA 功能描述:電流型 PWM 控制器 W/ANNEAL DL SWITCHER W/DRR OPTION 30V 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
ISL6225CAZA-T 功能描述:電流型 PWM 控制器 W/ANNEAL DL SWITCHER W/DRR OPTION 30V 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
ISL6225CAZ-T 功能描述:IC CTRLR DDR DRAM, SDRAM 28QSOP 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
ISL6226 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:Advanced PWM and Linear Power Controller for Portable Applications
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