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ISL97692, ISL97693, ISL97694A
Theory of Operation
The reciprocal of this calculation gives the effective resolution of
the PWM control per Equation 4:
PWM Resolution = -------------------------------------------------------------------------------
PWM Boost Converter
The current mode PWM boost converter produces the minimal
voltage needed to enable the LED stack with the highest forward
1
80ns × Input PWM Frequency
(EQ. 4)
voltage drop to run at the programmed current. The
ISL97692/3/4A employs current mode control boost
For example, for a 200Hz input PWM frequency, the minimum
duty cycle is:
PWM Resolution = -------------------------------------- = 14286 = 13.5bits
architecture that has a fast current sense loop and a slow voltage
feedback loop. This architecture achieves the fast transient
response, which is essential for portable product backlight
applications where the backlight must not flicker when the
power source is changed from a drained battery to an AC/DC
adapter.
Min Duty Cycle = 350ns × 200Hz = 0.007%
The effective resolution at 200Hz is 13? bits:
1
80ns × 200Hz
(EQ. 5)
(EQ. 6)
The number of LEDs that can be driven by ISL97692/3/4A
depends on the type of LED chosen in the application. The
maximum output is 26V at 40mA from 2.7V input.
Enable
Take the EN input high to enable the ISL97692/3/4A for normal
operation and low to enter low-power shutdown.
Dimming Controls
The ISL97692/3/4A allows the LED current to be programmed in
the range 2mA to 40mA (ISL97692) or 2mA to 30mA
(ISL97693/4A) by R SET per Equation 1:
Phase Shift Control
The ISL97692/4A are capable of delaying the phase of each
current source. Conventional LED drivers exhibit the worst load
transients to the boost circuit by turning on all channels
simultaneously, as shown in Figures 21 and 23. In contrast, the
ISL97692/4A phase shift each channel by turning them on once
during each PWM dimming period, as shown in Figures 22 and
24. At each dimming duty cycle (except at 100%) the sum of the
phase shifted total current will be less than a conventional LED
drivers’ total current.
For ISL97692/4A, the channels are separated by 360°/N, where
N is number of channels enabled. For example, if 3 channels are
I LEDmax = ---------------
1066
R SET
(EQ. 1)
enabled, they will be separated by 120°.
If the channels are combined for higher current application, the
Where:
- R SET is the resistor from ISET pin to GND ( Ω)
- I LEDmax is the peak current set by resistor R SET (A)
For example, if the required LED current (I LEDmax ) is 40mA, then
the R SET value needed is:
phase shift function must be disabled by connecting the ENPS
pin to ground.
ILED1-20mA
ILED2-20mA
R SET = 1066 ? 0.04 = 26.65k Ω
(EQ. 2)
ILED3-20mA
Choose the nearest standard resistor: 26.65k Ω, 0.1%
Direct PWM Dimming
The ISL97693 always operates in Direct PWM dimming mode.
ILED4-20mA
ILED_Total_80mA
The ISL97692 and ISL97694A can be selected to operate in
5
10
15
Direct PWM dimming mode by connecting the FPWM pin to VIN
and the SCL pin of ISL97694A must be tied to GND.
With Direct PWM, the channel outputs follow the input PWM
signal’s frequency and pulse width, as provided to the PWMI pin.
When PWMI is high, all channels sink the current set by the R SET
resistor. When PWMI is low, all channels are high-Z.
The maximum allowed input PWM frequency at PWMI is 30kHz.
The minimum duty is calculated by Equation 3 according to the
input PWM frequency, and is set by the minimum channel
on-time of 350ns.
TIME (ms)
FIGURE 21. CONVENTIONAL 4-CH LED DRIVER WITH 10% PWM
DIMMING CHANNEL CURRENT (UPPER) AND TOTAL
CURRENT (LOWER)
Min Duty Cycle = 350ns × Input PWM Frequency
15
(EQ. 3)
FN7839.4
December 20, 2012
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相关代理商/技术参数
ISL97694AIRTZ
制造商:Intersil Corporation 功能描述:6 CH W/12-BIT PWM DIMMING SINGLE CELL LI-ION BATTERY POWERED - Rail/Tube 制造商:Intersil Corporation 功能描述:IC LED DRVR BACKLIGHT 20TQFN
ISL97694AIRTZ-T
制造商:Intersil Corporation 功能描述:6 CH W/12-BIT PWM DIMMING SINGLE CELL LI-ION BATTERY POWERED - Tape and Reel 制造商:Intersil Corporation 功能描述:IC LED DRVR BACKLIGHT 20TQFN
ISL97694AIRTZ-TK
功能描述:LED照明驱动器 6CH w/12Bit Dimming Li-Ion LED Driver RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
ISL97698IIZ-T
制造商:Intersil Corporation 功能描述:HIGH EFFICIENCY 2 STRING LED DRIVER FOR SMARTPHONESWLCSP 12 - Tape and Reel 制造商:Intersil Corporation 功能描述:IC LED DRVR BACKLIGHT 12WLCSP
ISL97701IRZ
功能描述:直流/直流开关转换器 BOOST W/ INTEGRATED SCHOTKY & INPUT DISC RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
ISL97701IRZ-T13
功能描述:IC REG BOOST ADJ 0.1A 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:两者兼有 输出数:1 输出电压:5V，1 V ~ 10 V 输入电压:3.5 V ~ 28 V PWM 型:电流模式 频率 - 开关:220kHz ~ 1MHz 电流 - 输出:600mA 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:16-SSOP（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:16-QSOP
ISL97701IRZ-T7
功能描述:IC REG BOOST ADJ 0.1A 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:1 系列:EZBuck™ 类型:降压（降压） 输出类型:可调式 输出数:1 输出电压:0.8 V ~ 22.1 V 输入电压:3 V ~ 26 V PWM 型:电流模式 频率 - 开关:1.5MHz 电流 - 输出:1.8A 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-WFDFN 裸露焊盘 包装:剪切带 (CT) 供应商设备封装:8-DFN（2x2） 其它名称:785-1276-1
ISL97702IRZ
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