- 您现在的位置：买卖IC网 > Sheet目录335 > ISL97671AIRZ (Intersil)IC LED DVR PWM CTRL 6CH 20QFN
ISL97671A
Output Capacitors
The output capacitor smooths the output voltage and supplies
load current directly during the conduction phase of the power
switch. Output ripple voltage consists of discharge and charge of
the output capacitor during FET On and OFF time and the voltage
drop due to flow through the ESR of the output capacitor. The
ripple voltage can be shown as Equation 23:
Applications
High-Current Applications
Each channel of the ISL97671A can support up to 30mA
(50mA @ V IN = 12V). For applications that need higher current,
multiple channels can be grouped to achieve the desired current
(Figure 37). For example, the cathode of the last LED can be
Δ V CO = ( I O ? C O × D ? f S ) + ( ( I O × ESR )
(EQ. 23)
connected to CH0 through CH2; this configuration can be treated
as a single string with 90mA current driving capability.
The conservation of charge principle shown in Equation 21 also
indicates that, during the boost switch Off period, the output
capacitor is charged with the inductor ripple current, minus a
relatively small output current in boost topology. As a result, the
user must select an output capacitor with low ESR and adequate
input ripple current capability.
Note: Capacitors have a voltage coefficient that makes their
effective capacitance drop as the voltage across them increases.
C OUT in Equation 23 assumes the effective value of the capacitor
at a particular voltage and not the manufacturer’s stated value,
measured at 0V.
The value of Δ V Co can be reduced by increasing C O or f S , or by
using small ESR capacitors. In general, ceramic capacitors are
the best choice for output capacitors in small- to medium-sized
LCD backlight applications, due to their cost, form factor, and low
ESR.
A larger output capacitor also eases driver response during the
PWM dimming Off period, due to the longer sample and hold
effect of the output drooping. The driver does not need to boost
harder in the next On period that minimizes transient current.
The output capacitor is also needed for compensation, and in
general, 2x4.7μF/50V ceramic capacitors are suitable for
notebook display backlight applications.
Output Ripple
Δ V Co , can be reduced by increasing Co or f SW , or using small ESR
capacitors. In general, ceramic capacitors are the best choice for
output capacitors in small to medium sized LCD backlight
applications due to their cost, form factor, and low ESR.
A larger output capacitor will also ease the driver response
during PWM dimming Off period due to the longer sample and
hold effect of the output drooping. The driver does not need to
boost harder in the next On period that minimizes transient
current. The output capacitor is also needed for compensation,
and, in general 2x4.7μF/50V ceramic capacitors are suitable for
notebook display backlight applications.
Schottky Diode
A high-speed rectifier diode is necessary to prevent excessive
voltage overshoot. Schottky diodes are recommended because
of their fast recovery time, low forward voltage and reverse
leakage current, which minimize losses. The reverse voltage
rating of the selected Schottky diode must be higher than the
maximum output voltage. Also the average/peak current rating
of the Schottky diode must meet the output current and peak
inductor current requirements.
25
V OUT
CH0
CH1
CH2
FIGURE 37. GANGING MULTIPLE CHANNELS FOR HIGH CURRENT
APPLICATIONS
Low Voltage Operations
The ISL97671A VIN pin can be separately biased from the LED
power input to allow low-voltage operation. For systems that have
only a single supply, V OUT can be tied to the driver VIN pin to allow
initial start-up (Figure 38). The circuit works as follows: when the
input voltage is available and the device is not enabled, V OUT
follows V IN with a Schottky diode voltage drop. The V OUT
boot-strapped to the VIN pin allows initial start-up, once the part
is enabled. Once the driver starts up with V OUT regulating to the
target, the VIN pin voltage also increases. As long as V OUT does
not exceed 26.5V and the extra power loss on V IN is acceptable,
this configuration can be used for input voltage as low as 3.0V.
The Fault Protection FET feature cannot be used in this
configuration.
For systems that have dual supplies, the VIN pin can be biased
from 5V to 12V, while input voltage can be as low as 2.7V
(Figure 39). In this configuration, VBIAS must be greater than or
equal to VIN to use the fault FET.
FN7709.3
November 30, 2012
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
ISL97672AIRZ
IC LED DRVR LOW DIMMING 20QFN
ISL97672BIRZ
IC LED DRVR BACKLIGHT 20QFN
ISL97675IRZ-TK
IC LED DVR PWM CTRL 4CH 20QFN
ISL97677IRZ
IC LED DVR PWM CTRL 8CH 32QFN
ISL97678IRZ
IC LED DVR PWM DIMMING 8CH 32QFN
ISL97686IRTZ
IC LED DRVR BACKLIGHT 28TQFN
ISL97691IRTZ-TK
IC LED DRVR BACKLIGHT 3D 16TQFN
ISL97693IRTZ-TK
IC LED DRVR BACKLIGHT 16TQFN
相关代理商/技术参数
ISL97671AIRZ-T
功能描述:IC LED DRVR 6-CH BACKLIGHT 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C
ISL97671AIRZ-TK
功能描述:IC LED DVR PWM CTRL 6CH 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C
ISL97671IRZ
制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH I2C CONTROL - Rail/Tube
ISL97671IRZ-EVALZ
功能描述:BOARD EVALUATION FOR ISL97671 RoHS:是 类别:编程器，开发系统 >> 评估板 - LED 驱动器 系列:- 标准包装:1 系列:PowerWise® 电流 - 输出 / 通道:20mA 输出及类型:1，非隔离 输出电压:17V 特点:可调光 输入电压:2.7 ~ 5.5 V 已供物品:板 已用 IC / 零件:LM3508 相关产品:LM3508TLX-ND - IC LED DRVR WHT BCKLGT 9USMDLM3508TLDKR-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLCT-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLTR-ND - IC LED DRVR WHT BCKLGT 9MICROSMD
ISL97671IRZ-T
制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH I2C CONTROL - Tape and Reel
ISL97671IRZ-TK
制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH I2C CONTROL, 1K T&R - Tape and Reel
ISL97672AIRZ
功能描述:IC LED DRVR LOW DIMMING 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C
ISL97672AIRZ-T
功能描述:IC LED DRVR LOW DIMMING 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C