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Application Note 1247
Output Voltage Ripple
The evaluation platform is designed to meet a core voltage
ripple specification of 20mV. Board performance is shown in
Load
Load
Figure 4, under room temperature conditions and light
loading. The output voltage ripple measures less than 18mV.
Adjustment of output voltage ripple is addressed in the
Adapting Circuit Performance section.
Load
Load
VOUT1, 20mV/div
Power
Indicator
Input Power
Supply
FIGURE 2. EXTERNAL POWER SUPPLY AND LOAD
CONNECTIONS
ISL6521EVAL1 Performance
Enabling the Controller
Once the bias voltage applied to the PWM controller reaches
the rising Power-On Reset (POR) threshold, the ISL6521
initiates a soft-start interval. The point at which the ISL6521
reaches the rising POR threshold is indicated as Soft-start
Begins in Figure 3. After a short delay, the four outputs
begin ramping to the output levels set by external resistor
dividers to the FB pins. The controlled voltage ramp of all
four outputs charges the output capacitors of each output
slowly and softens the initial current drawn from the bias
supply. Reducing the soft-start interval lasts about 3ms and
ends just after all four output reach their programmed output
levels. The point soft-start ends is indicated as Soft-start
Ends in Figure 3.
PHASE, 5V/div
5 μ s/div
FIGURE 4. CORE VOLTAGE RIPPLE (VOUT1)
Protection Features
The ISL6521 features overcurrent protection on the PWM
controller. The linear controllers feature undervoltage
protection which doubles as overcurrent protection.
The PWM controller uses the upper MOSFET’s on-resistance,
r DS(on) , to monitor the current flow through the device. This
current level is then compared internally to the overcurrent trip
point set externally. The overcurrent protection monitors these
conditions on a cycle by cycle basis. When the overcurrent
trip level is exceeded, the PWM controller removes gate drive
to the MOSFETs. The ISL6521 then enters a wait period
equivalent to three soft-start intervals. A soft-start interval
follows and if the overcurrent condition remains, the controller
will trip off again. This results in the hiccup mode response to
a sustained short shown in Figure 5. The PWM controller exits
Soft-start Begins
Soft-start Ends
VOUT2, 1V/div
this mode once the output voltage soft-starts successfully or
bias is removed from the controller.
VCC, 2V/div
VOUT3, 1V/div
VOUT4, 1V/div
OC Event Occurs
VOUT1, 0.5V/div
VOUT1, 1V/div
IOUT1, 5A/div
1ms/div
FIGURE 3. SOFT-START INTERVAL
20ms/div
FIGURE 5. HICCUP MODE OVERCURRENT PROTECTION
2
AN1247.0
July 10, 2006
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相关代理商/技术参数
ISL6521EVAL1Z 功能描述:EVALUATION BOARD 1 ISL6521 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
ISL6521IBZ 功能描述:电压模式 PWM 控制器 4 IN 1 PWM/LINEAR CNTRLR 5V RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel
ISL6521IBZ-T 功能描述:电压模式 PWM 控制器 4 IN 1 PWM/LINEAR CNTRLR 5V RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel
ISL6522ACB 功能描述:IC REG CTRLR BST PWM VM 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR)
ISL6522ACB-T 功能描述:IC REG CTRLR BST PWM VM 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR)
ISL6522ACR 功能描述:IC REG CTRLR BST PWM VM 16-QFN RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR)
ISL6522ACR-T 功能描述:IC REG CTRLR BST PWM VM 16-QFN RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR)
ISL6522BCB 功能描述:IC REG CTRLR BST PWM VM 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR)