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| 型号： | ISL97686IRTZ-T |
| 厂商： | Intersil |
| 文件页数： | 12/23页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR BACKLIGHT 28TQFN |
| 标准包装： | 6,000 |
| 拓扑： | 线性（LDO），PWM，升压（升压） |
| 输出数： | 4 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 汽车，背光，通用型 |
| 频率： | 200kHz ~ 1.2MHz |
| 电源电压： | 9 V ~ 32 V |
| 输出电压： | 75V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 105°C |
ISL97686
V SYNC FUNCTION
The V SYNC function is used to provide accurate LED dimming
frequencies and make sure that the video data is properly
aligned with the frame rate. A phase locked loop (PLL) is used to
lock the frequency to a multiple of the frame rate. Additionally,
the phase of the PWM output is aligned with the frame rate to
provide very predictable video performance. In V SYNC mode, the
FPWM pin is used as the PLL loop compensation pin and needs a
loop filter connected between it and ground.
Frame rates between 30Hz and 300Hz are supported, and an
automatic frequency detection circuit will provide the same
output frequency at 30, 60, 120, 180, 240, and 300Hz.
Additionally, the PWM dimming frequency can be pre-selected to
any of the following values shown in Table 1 (Note that for the
60Hz range, the frequencies will be scaled by a factor of
framerate/60Hz and for the 120Hz range they will be scaled by a
factor of framerate/120Hz).
TABLE 1. PRE-SELECTED PWM DIMMING FREQUENCY AT V SYNC MODE
DIMMING FREQUENCY
(Hz) (kHz) (kHz) (kHz)
inductor current to the required level to support the load. For
example, a 1% on-time while running at 20kHz PWM dimming
frequency is only 500ns. If the boost switching frequency is set at
500kHz, this only represents a quarter of a switching cycle per
LED on-time, which may not be sufficient to ramp the inductor
current to the required level.
The ISL97686 incorporates an additional PFM switching
mechanism that allows the boost stage to continue to switch at
low current levels in order to replace the energy lost from the
output capacitor due to the OVP stack resistance and capacitor
self discharge. For very short pulses, this also means that the
charge delivered to the LEDs in the on-times is provided entirely
by the output capacitor, kept at the correct voltage by the PFM
mode in the off-times. This allows the output to always remain
very close to the required level, so that when the LEDs are
re-enabled, the boost output is already at the correct level. This
dramatically improves LED PWM performance, providing industry
leading linearity down to sub 1% levels, and reduces the
overshoots in the boost inductor current, caused by transient
switching when the LEDs are switched on, to a minimum.
The system will continue to maintain V OUT at the target level for
120ms after the last time the LEDs were on. If all LEDs are off for
180
240
300
360
420
480
1.26
1.38
1.50
1.62
1.74
1.86
5.70
6.18
6.66
7.14
7.62
8.10
13.38
13.86
14.34
14.82
15.30
15.78
a longer period than this, the converter will stop switching and go
into a sleep mode, allowing V OUT to decay, in order to save power
during long backlight-off periods.
Switching Frequency
The boost switching frequency can be adjusted by the resistor on
the OSC pin, which must be connected to AGND, and follows
Equation 4:
( 5 × 10
)
f SW = -----------------------
540
600
1.98
2.10
8.58
9.06
16.26
16.74
10
R OSC
(EQ. 4)
660
720
780
840
900
960
1.02k
1.14k
2.34
2.58
2.88
3.36
3.78
4.20
4.74
5.22
9.54
10.02
10.50
10.98
11.46
11.94
12.42
12.90
17.22
17.70
18.18
18.66
19.14
19.62
20.10
20.58
where f SW is the desirable boost switching frequency and R OSC is
the setting resistor.
5V and 2.4V Low Dropout Regulators
A 5V LDO regulator is used to provide the low voltage supply
needed to drive internal circuits. The output of this LDO is the VDC
pin. A decoupling capacitor of 1μF or more is required between
this pin and AGND for correct operation. Similarly, a 2.4V LDO
regulator is present at the VLOGIC pin, and also requires a 1μF
decoupling capacitor. Both pins can be used as a coarse voltage
reference, or as a supply for other circuits, but can only support a
load of up to ~10mA and should not be used to power noisy
V OUT Control when LEDs are Off
When the backlight is enabled but all LEDs are off (i.e., during the
PWM off times), the switching regulator of a typical LED driver will
stop switching, which can allow the output to begin to discharge.
circuits that can feed significant noise onto their supply.
Soft-Start and Boost Current Limit
The boost current limit should be set by using a resistor from CS
to PGND. The typical current limit can be calculated as:
I LIMIT = ------------
This is not a problem when the LED off times are short and the
duty cycle is running at a high duty cycle, or the output
0.17
R CS
(EQ. 5)
capacitance is large. However, it presents two problems. First, for
low duty cycles at low frequencies, V OUT can droop between
on-times, resulting in under-regulation of the current when the
LEDs are next switched on. Second, at high PWM frequencies or
very low duty cycles, LED on-times can be shorter than the
minimum number of boost cycles needed to ramp up the
12
The CS resistor should be chosen based on the maximum load
that needs to be driven. Typically, a limit of 30~40% more than is
required under DC conditions is sufficient to allow for necessary
overshoots during load transients. Values of 20~100m ? are
supported.
FN7953.0
April 23, 2012
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| ISL97687IBZ | 功能描述:IC LED DRVR 4 CHAN PWM 28SOIC 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 |
| ISL97687IBZEV1Z | 制造商:Intersil 功能描述:ISL97687 EVAL |
| ISL97687IBZ-T | 功能描述:IC LED DRVR 4 CHAN PWM 28SOIC 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 |
| ISL97687IRTZ | 功能描述:IC LED DRVR 4 CHAN PWM 28TQFN 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 |
| ISL97687IRTZ-T | 功能描述:IC LED DRVR 4 CHAN PWM 28TQFN 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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