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参数资料
| 型号： | ISL97672BIRZ |
| 厂商： | Intersil |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR BACKLIGHT 20QFN |
| 标准包装： | 75 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 6 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 频率： | 200kHz ~ 1.5MHz |
| 电源电压： | 4.5 V ~ 26.5 V |
| 输出电压： | 45V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-VFQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN（3x4） |
| 包装： | 管件 |
| 工作温度： | -40°C ~ 85°C |
ISL97672B
IC Protection Features and Fault
Management
ISL97672B has several protection and fault management
features that improve system reliability. The following sections
describe them in more detail.
IN-RUSH CONTROL AND SOFT-START
The ISL97672B has separate, built-in, independent in-rush
control and soft-start functions. The in-rush control function is
built around an external short-circuit protection P-channel FET in
series with VIN. At start-up, the fault protection FET is turned on
slowly due to a 21μA pull-down current output from the FAULT
pin. This discharges the fault FET's gate-source capacitance,
turning on the FET in a controlled fashion. As this happens, the
output capacitor is charged slowly through the low-current FET
before it becomes fully enhanced. This results in a low in-rush
current. This current can be further reduced by adding a
capacitor (in the 1nF to 5nF range) across the gate source
terminals of the FET.
Once the chip detects that the fault protection FET is turned on
fully, it assumes that in-rush is complete. At this point, the boost
regulator begins to switch, and the current in the inductor ramps
up. The current in the boost power switch is monitored, and
switching is terminated in any cycle in which the current exceeds
the current limit. The ISL97672B includes a soft-start feature in
which this current limit starts at a low value (275mA). This value
is stepped up to the final 2.2A current limit in seven additional
steps of 275mA each. These steps happen over at least 8ms and
are extended at low LED PWM frequencies if the LED duty cycle is
low. This extension allows the output capacitor to charge to the
required value at a low current limit and prevents high input
current for systems that have only a low to medium output
current requirement.
For systems with no master fault protection FET, the in-rush
current flows towards C OUT when V IN is applied. The in-rush
current is determined by the ramp rate of V IN and the values of
C OUT and L.
FAULT PROTECTION AND MONITORING
The ISL97672B features extensive protection functions to cover
all perceivable failure conditions. The /FLAG pin is a latched
open-drain output that monitors string open, LED short, V OUT
short, and overvoltage and over-temperature conditions. This pin
resets only when input power is recycled or the part is re-enabled.
The failure mode of an LED can be either an open circuit or a
short. The behavior of an open-circuited LED can additionally
take the form of either infinite resistance or, for some LEDs, a
Zener diode, which is integrated into the device in parallel with
the now-opened LED.
step changes in LED duty cycle) can transiently look like LED
fault modes. The ISL97672B uses feedback from the LEDs to
determine when it is in a stable operating region and prevents
apparent faults during these transient events from allowing any
of the LED stacks to fault out. See Table 1 for details.
A fault condition that results in an input current that exceeds the
device’s electrical limits will result in a shutdown of all output
channels.
SHORT-CIRCUIT PROTECTION (SCP)
The short-circuit detection circuit monitors the voltage on each
channel and disables faulty channels that are above approximately
7.5V (this action is described in Table 1 on page 12).
OPEN-CIRCUIT PROTECTION (OCP)
When one of the LEDs becomes an open circuit, it can behave as
either an infinite resistance or as a gradually increasing finite
resistance. The ISL97672B monitors the current in each channel
such that any string that reaches the intended output current is
considered “good.” Should the current subsequently fall below the
target, the channel is considered an “open circuit.” Furthermore,
should the boost output of the ISL97672B reach the OVP limit, or
should the lower over-temperature threshold be reached, all
channels that are not good are immediately considered to be open
circuit. Detection of an open circuit channel results in a time-out
before the affected channel is disabled. This time-out is sped up
when the device is above the lower over-temperature threshold, in
an attempt to prevent the upper over-temperature trip point from
being reached.
Some users employ special types of LEDs that have a Zener
diode structure in parallel with the LED. This configuration
provides ESD enhancement and enables open-circuit operation.
When this type of LED is open circuited, the effect is as if the LED
forward voltage has increased but the lighting level has not
increased. Any affected string will not be disabled, unless the
failure results in the boost OVP limit being reached, which allows
all other LEDs in the string to remain functional. In this case, care
should be taken that the boost OVP limit and SCP limit are set
properly, to ensure that multiple failures on one string do not
cause all other good channels to fault out. This condition could
arise if the increased forward voltage of the faulty channel
makes all other channels look as if they have LED shorts. See
Table 1 for details of responses to fault conditions.
OVP AND V OUT
The Overvoltage Protection (OVP) pin has a function of setting the
overvoltage trip level as well as limiting the V OUT regulation
range.
The ISL97672B OVP threshold is set by R UPPER and R LOWER such
that:
V OUT_OVP = 1.22Vx --------------------------------------------------------
For basic LEDs (which do not have built-in Zener diodes), an
open-circuit failure of an LED results only in the loss of one
( R U PP E R + R L O WE R )
R L O WE R
(EQ. 5)
channel of LEDs, without affecting other channels. Similarly, a
short-circuit condition on a channel that results in that channel
being turned off does not affect other channels unless a similar
fault is occurring.
Due to the lag in boost response to any load change at its output,
certain transient events (such as LED current steps or significant
10
and V OUT can only regulate between 60% and 100% of the
V OUT_OVP such that:
Allowable V OUT = 60% to 100% of V OUT_OVP
if, for example, 10 LEDs are used with the worst-case V OUT of
35V.
FN7995.1
November 22, 2013
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL97672BIRZ-T | 功能描述:IC LED DRVR BACKLIGHT 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 |
| ISL97672IRZ | 制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH PWM DIMMING - Rail/Tube 制造商:Intersil 功能描述:6-CH LED DRVR W/PWM DIM |
| ISL97672IRZ-T | 制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH PWM DIMMING, T&R - Tape and Reel 制造商:Intersil 功能描述:6-CH LED DRVR W/PWM DIM |
| ISL97672IRZ-TK | 制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH PWM DIMMING, 1K T&R - Tape and Reel 制造商:Intersil 功能描述:6-CH LED DRVR W/PWM DIM 1K |
| ISL97673IRZ | 制造商:Intersil Corporation 功能描述:6-CH LED DRIVER WITH SMBUS OR PWM DIMMING AND PHASE SHIFT CO - Rail/Tube 制造商:Intersil 功能描述:6-CH LED DRVR W/SMBU OR PWM DIM & PHS |
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