参数资料
| 型号： | ISL6444CAZ-T |
| 厂商： | Intersil |
| 文件页数： | 9/19页 |
| 文件大小： | 0K |
| 描述： | IC CONTROLLER DDR 28-QSOP |
| 标准包装： | 2,500 |
| 应用： | 控制器，DDR |
| 输入电压： | 4.5 V ~ 24 V |
| 输出数： | 2 |
| 输出电压： | 0.9 V ~ 5.5 V |
| 工作温度： | -10°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 28-SSOP/QSOP |
| 包装： | 带卷 (TR) |
ISL6444
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.
Vin
Q1
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.
UGATE
ISEN
R CS
L1
VOUT
Q2
C1
Cz
R1
t
LGATE
VOUT
VSEN
OCSET
IIND
PHASE
t
ISL6444
R OC
R2
COMP
1 2 3 4 5 6 7 8
t
FIGURE 2. OUTPUT VOLTAGE PROGRAM
MODE
OF
OPERATION
PWM
Hysteretic
t
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
FIGURE 3. CCM -- HYSTERETIC TRANSITION
losses associated with it.
The critical value of the inductor current can be estimated by
the following expression.
VOUT
t
2 ? F SW ? L O ? V IN
( V IN – V O ) ? V O
I HYS = --------------------------------------------------
(EQ. 4)
IIND
1
2 3 4 5
6 7 8
t
To improve converter efficiency in loads lower than critical,
the switch-over to variable frequency hysteretic operation
PHASE
COMP
t
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
MODE
OF
OPERATION
Hysteretic
PWM
t
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.
FIGURE 4. HYSTERETIC -- CCM TRANSITION
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:
Δ V hys
To prevent chatter between operating modes, the circuit
looks for eight sequential matching sign signals before it
2 ? ESR
I CCM ≈ ----------------------
(EQ. 5)
makes its decision to perform a mode change. The same
algorithm is true for both CCM-hysteretic and hysteretic-
CCM transitions.
9
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
FN9069.3
April 12, 2007
相关PDF资料 |
PDF描述 |
|---|---|
| HBC13DRXH-S734 | CONN EDGECARD 26POS DIP .100 SLD |
| 450USG270MEFCSN22X50 | CAP ALUM 270UF 450V 20% SNAP-IN |
| GCB92DHHN-S378 | CONN EDGECARD 184POS 5V .050 SLD |
| HMC13DRXI-S734 | CONN EDGECARD 26POS DIP .100 SLD |
| GCB92DHHD-S378 | CONN EDGECARD 184POS 5V .050 SLD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL6445EVAL3Z | 功能描述:EVALUATION BOARD FOR ISL6445 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL6445IAZ | 功能描述:IC REG CTRLR BUCK PWM CM 24-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL6445IAZS2695 | 制造商:Intersil Corporation 功能描述: |
| ISL6445IAZ-TK | 功能描述:IC REG CTRLR BUCK PWM CM 24-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL6445IAZ-TKS2645 | 制造商:Intersil Corporation 功能描述:DC DC CNTRLR DUAL-OUT STEP DOWN 4.5V TO 24V 24QSOP W - Tape and Reel |
发布紧急采购，3分钟左右您将得到回复。