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参数资料
| 型号： | A6268KLPTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 13/19页 |
| 文件大小： | 0K |
| 描述： | IC LED CTLR AUTOMOBILE 16TSSOP |
| 标准包装： | 1 |
| 恒定电流： | 是 |
| 拓扑： | 低端，PWM，SEPIC，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： | 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： | 标准包装 |
| 工作温度： | -40°C ~ 150°C |
| 其它名称： | 620-1473-6 |
A6268
Automotive High Current LED Controller
tion by setting FF2 to high impedance. However, the A6268 will
continue to drive the output. When the output again reaches the
required current level, FF2 will go low.
Output Short – 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. An output short is detected when both a
shorted LED and an LED undercurrent condition occur (defined
previously). If the above two conditions occur, the A6268 will set
FF1 high impedance. Note that at start-up, or during pulse width
modulation of the Enable pin, a fault blank period, t FB , occurs
before this fault detection circuitry becomes active.
LED Sense Resistor Overcurrent – Under some circuit fault
conditions, for example in boost mode, if the cathode connec-
tion is pulled to VBAT , the control loop can no longer control
the LED current to the target level. If the voltage across the LED
sense resistor, R SS , increases above the target sense voltage,
V IDL , by an amount that is more than the overcurrent voltage
difference, V OVCL , the A6268 will indicate a LED overcurrent by
setting FF1 high impedance.
Note that even if FF1 drives a supply isolation FET, the sense
resistor may still be damaged because it is effectively between
VBAT and GND. Note that at startup, or during pulse width
modulation of the Enable pin, a fault blank period, t FB , occurs
before this fault detection circuitry becomes active.
Also in boost mode, if a “soft” short is applied across an LED
string, causing the string voltage to be less than the input voltage,
the control loop may not control as described previously and FF1
will be set. Alternatively, a soft short may cause a shorted LED
string, as described in the section Shorted LED String. The actual
detection of a soft short, whether by shorted LED string or LED
sense resistor overcurrent detection, will depend on the actual
application setup.
LED Sense Resistor Negative Overcurrent – Under some
circuit fault conditions, for example in buck-boost mode, if the
cathode connection is pulled to GND, current will flow through
the sense resistor, R SS , in the opposite direction. If the voltage
across the sense resistor exceeds the negative overcurrent thresh-
old, V NOCL , the A6268 will set FF1 high impedance.
Note that if FF1 does not drive a supply isolation FET, the sense
resistor may be damaged. Also, note that the fault blank period
will not be applied if this fault is present at startup, or during
pulse width modulation of the Enable pin, because it is always
regarded as a non-standard condition.
Shorted LED Stack – A short circuit across the LED stack, is
detected when:
V STR < V SCL (13)
If the above condition occurs, the A6268 will indicate an LED
overcurrent by setting FF1 high impedance. Note that at startup,
or during pulse width modulation of the Enable pin, a fault
blank period, t FB , occurs before this fault detection circuitry
becomes active.
Fault Flag One If any shorted condition occurs, including:
output short, LED sense resistor overcurrent, LED sense resistor
negative overcurrent, or shorted LED string, the A6268 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. Any of the
aforementioned faults will be latched and will only be cleared by
cycling the power, or by pulling EN low for a time greater than
the disable time (> t DIS ).
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
connected, as shown in figure 3, with the source connected to the
supply and the drain connected to the inductor of the converter.
Two pull-up resistors are used to limit the voltage across the gate-
source junction during high input voltages or load dump condi-
tions. If the battery voltage is restricted, one resistor across the
gate-source junction can be used. The FF1 provides a sink current
of typically 1.3 mA.
This circuit can be used to avoid most hazardous conditions and
protect the circuit components from over-stress. Note that under
extreme cases, the circuit cannot protect against certain fault
conditions as described in the following section.
RSL (buck boost)
V BAT
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
13
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