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| 型号： | ISL97671IRZ-EVALZ |
| 厂商： | Intersil |
| 文件页数： | 12/27页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR ISL97671 |
| 标准包装： | 1 |
| 电流 - 输出 / 通道： | 50mA |
| 输出及类型： | 6，非隔离 |
| 输出电压： | 45V |
| 输入电压： | 2.5V，3.3V |
| 已供物品： | 板 |
| 已用 IC / 零件： | ISL97671 |
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ISL97671
The default PWM dimming is in DPST mode. In all three
methods, the average LED current of each channel is controlled
by I LED and the PWM duty cycle in percent, as shown in
Equation 6:
For example, if the SMBus/I 2 C controlled PWM duty is 80%
dimming at 200Hz (see Equation 12) and the external PWM duty
cycle is 60% dimming at 1kHz, the resultant PWM duty cycle is
48% dimming at 200Hz.
I LED ( ave ) = I LED × PWM
(EQ. 6)
PWM Dimming Frequency Adjustment
6.66 × 10
F PWM = ------------------------
I LED ( ave ) = I LED × ( BRT ? 255 )
I LILED ( ave ) = I LED × PWMI
Method 1 (Internal Mode, SMBus/I 2 C controlled PWM)
The average LED current of each channel is controlled by the
internally generated PWM signal, as shown in Equation 7:
(EQ. 7)
where BRT is the PWM brightness level programmed in the
Register 0x00. BRT ranges from 0 to 255 in decimal and defaults
to 255 (0xFF). BRT = 0 disconnects all channels.
To use only the SMBus/I 2 C controlled PWM brightness control,
users need to set Register 0x01 to 0x05 with EN/PWM in logic
high.
The SMBus/I 2 C controlled PWM frequency is adjusted by a
resistor at the FPWM pin, which will be described in “PWM
Method 2 (External Mode)
The average LED current of each channel can also be controlled by
an external PWM signal, as shown in Equation 8:
(EQ. 8)
The PWM dimming frequency can be set (see PWM Dimming
Frequency Adjustment section) or applied up to 30kHz with duty
cycles from 0.4% to 100%. The PWM dimming off time cannot be
longer than 28ms or else the driver will enter shutdown.
To use externally applied PWM signal only for brightness control,
users need to set Register 0x01 to 0x03.
Method 3 (DPST Mode)
The average LED current of each channel can also be controlled
by the product of the SMBus/I 2 C controlled PWM and the
external PWM signals as:
The PWM dimming frequency is set by an external resistor at the
FPWM pin as:
7
(EQ. 12)
RFPWM
where F PWM is the desirable PWM dimming frequency and
R FPWM is the setting resistor.
The PWM dimming frequency can be set or applied up to 30kHz
with duty cycle from 0.4% to 100%.
Phase Shift Control
The ISL97671 is capable of delaying the phase of each current
source to minimize load transients. By default, phase shifting is
disabled as shown in Figure 21 where the channels PWM
currents are switching uniformly. The duty cycles can be
controlled by the data in PWM Brightness Control Register via the
SMBus/I 2 C interface, an external PWM signal with the frequency
set by the RFPWM, or by an external PWM signal with the
frequency set by the incoming signal.
t FPWM
ILED0 t ON t OFF
ILED1
ILED2
ILED3
ILED4
ILED5
FIGURE 21. NO DELAY (DEFAULT PHASE SHIFT DISABLED)
t D1 = ------------------ x ? ---------- ?
t FPWM 255
? N ?
I LED ( ave ) = I LED xPWM DPST
Where:
PWM DPST = BRT ? 255 × PWMI
Therefore:
I LED ( ave ) = I LED × BRT ? 255 × PWMI
(EQ. 9)
(EQ. 10)
(EQ. 11)
When EqualPhase = 1, the phase shift evenly spreads the channels
switching across the PWM cycle, depending on how many channels
are enabled, as shown in Figures 22 and 23. Equal phase means
there are fixed delays between channels and such delay can be
calculated as:
(EQ. 13)
255
t D2 = ------------------ x 255 – ( N – 1 ) ? ---------- ? ?
t FPWM ? 255
? N ? ?
?
255
Where BRT is the value held in Register 0x00 (default setting
0xFF) controlled by SMBus/I 2 C and PWM is the duty cycle of the
incoming PWM signal. In this way, the users can change the
PWM current in ratiometric manner to achieve DPST compliance
backlight dimming.
To use the DPST mode, users need to set Register 0x01 to 0x01
with external PWM signal.
The DPST mode PWM frequency is adjusted by a resistor at the
12
(EQ. 14)
where (255/N) is rounded down to the nearest integer. For
example, if N = 6, (255/N) = 42, that leads to:
t D1 = t FPWM x 42/255
t D2 = t FPWM x 45/255
where t FPWM is the sum of t ON and t OFF . N is the number of LED
channels. The ISL97671 will detect the numbers of operating
channels automatically.
FN7631.3
August 14, 2012
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| ISL97671IRZ-T | 制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH I2C CONTROL - Tape and Reel |
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| 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 |
| ISL97672AIRZ-TK | 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 |
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