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参数资料
| 型号： | A6267KLPTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 11/17页 |
| 文件大小： | 0K |
| 描述： | IC LED CTLR AUTO HI CURR 16TSSOP |
| 标准包装： | 8,000 |
| 恒定电流： | 是 |
| 拓扑： | 低端，PWM，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 无 |
| 类型 - 主要： | 车载，背光 |
| 频率： | 100kHz ~ 700kHz |
| 电源电压： | 6.5 V ~ 50 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 供应商设备封装： | 16-TSSOP-EP |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 150°C |
A6267
Automotive High Current LED Controller
These measurements are used to determine if there is an open
circuit, if one or more LEDs are shorted, if the output is shorted,
or if there is a short across the LED string. Each condition is
described in turn in the following sections.
Open LED –An open circuit is evaluated when:
becomes a short circuit, then the remaining LEDs will continue
to be lit with the same current through, and voltage across,
each LED.
Note—Accuracy: The output status monitor relies on all the
LEDs in the load having a similar forward voltage drop. Where
V STR > V OCL
(7)
possible all the LEDs forming the load for a single controller
should be taken from the same voltage bin. With only two or
where V OCL is the LED open circuit voltage defined in the Elec-
trical Characteristics table.
Because the output is current-controlled it is possible for an open
circuit on the output to cause extremely high voltages to be pres-
ent. Therefore, to prevent any hazardous voltages or damage to
the circuits, the gate drive output, SG, is immediately driven low
when an open circuit is detected. After an open circuit fault has
been detected, FF2 will become high impedance, and the open
circuit fault state will remain until the open fault time-out period
toto, expires. When the gate drive output is re-enabled at the end
of the open fault time-out period, the output is again monitored
for an open circuit. If the open circuit is still present, then the
fault will again be flagged and the switch drive disabled. This
cycle will continue, as long as the open circuit condition is pres-
ent.
Note that the Fault Blank timer is not used when an open LED
fault occurs. This is to avoid potentially damaging voltages
appearing in the power circuitry.
Shorted LED – A short circuit on one or more LEDs is detected
when:
? for the first (reference) LED:
three LEDs a wider variation in forward voltage is acceptable,
but the selection of LEDs from the same bin is more critical when
higher numbers of LEDs are used in a single string.
Shorted LED String or Output Short – A short circuit across
the LED string, is detected when:
V STR < V SCL (10)
An output short can consist of the LP, LN, or LF terminals of
the LED string being shorted, either to the battery terminal or
to ground. Either a shorted LED string or output short will be
latched and will only be cleared by pulling EN low for a period
greater than the disable time, or by cycling the power.
If either a shorted LED string, or an output short is detected, the
A6267 will stop the switching action by pulling SG low. The
fault flag FF1 will go high impedance and should be pulled up to
the supply with suitable external pull-up resistors to indicate the
fault. Either a shorted LED string or output short will be latched
and will only be cleared by pulling EN low for a period greater
than the disable time, or by cycling the power.
The FF1 output can also be used with pull-up resistors and a
P-channel MOSFET in the supply, to isolate the switching ele-
ments and the load from the supply. This MOSFET should be
V STR > V LED + V SCOR
? for other than the first (reference) LED:
V LED > V STR + V SCO
(8)
(9)
connected, as shown in figure 3, with the source connected to the
supply and the drain connected to the inductor of the converter.
where V STR and V LED are as defined above, V SCO is the nonrefer-
ence LED short offset voltage, and V SCOR is the reference LED
short offset voltage. V SCO and V SCOR are defined in the Electrical
Characteristics table.
When a short is present, the fault flag FF2 is high impedance, but
the regulator continues to operate and drives the remaining LEDs
with the correct regulated current. FF2 will remain high imped-
ance while the short circuit condition is present.
A short circuit on one or more LEDs will not cause a hazard
because the output is current-controlled. If one LED fails and
VBAT
To VIN
To FF1
Figure 3. Example of a supply isolation MOSFET
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
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