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参数资料
| 型号： | A6268KLPTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 11/19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
the CKOUT pin of another A6268 as the external clock source.
In this case the switching point of each subsequent A6268 in the
chain will be delayed from that of the previous A6268, and the
current pulses will be spread across the oscillator period.
Diagnostics
The circuit includes several diagnostic and safety functions to
assist in ensuring safe operation of the LEDs, the A6268, and the
external components. When any fault is detected, one or both of
the fault flag outputs, FF1 and FF2, will be inactive (high imped-
ance, open drain) until the fault is removed. The action taken by
the A6268 when a fault occurs is defined in table 1. To be able to
If either FF1 is pulled low (due to an output short or overcur-
rent condition), or FF2 is pulled low when an open LED fault is
indicated, then the output disable will be overridden.
At start-up or during pulse width modulation of the Enable pin, a
fault blank period, t FB , occurs before the fault detection circuitry
becomes active. This period allows steady state conditions to
be established before fault monitoring takes place. Note that the
fault blank period is derived from the oscillator period by a ratio
of 1024:1, so any variation in the oscillator frequency will change
the fault blank period. For the default switching frequency of
350 kHz, this means the fault blank period would be:
monitor the state of FF1 and FF2, add a suitable external pull-up
resistor.
t FB = 1024 × (1 / 350 × 10 3 ) = 3 ms
Note that no fault blanking is applied to the following faults:
(6)
The A6268 will continue to drive the LEDs under most fault con-
ditions and will only disable the drive to the LEDs when a high
voltage hazard is present or the external components are likely
to be over-stressed. For output short circuits, LED sense resis-
tor overcurrents, LED sense resistor negative overcurrents, or
shorted LED string, the fault status is latched until a power cycle
occurs, or by pulling EN low for a time greater than the disable
time ( > t DIS ). In all other cases the drive will be re-established
when the hazard is removed.
open LED, LED sense resistor negative overcurrent, VIN under-
voltage, or VREG undervoltage.
VIN Undervoltage If the voltage at VIN drops below the
specified turn-off voltage, V INUV , the gate drive output, SG, will
be driven low and both fault flags, FF1 and FF2, will be high
impedance. VIN must rise above the turn-on threshold, V INUV +
? V INUV , before the A6268 can start up.
VREG Undervoltage If the voltage at VREG, V REG , drops
below the specified turnoff voltage, V REGUV , the gate drive
output, SG, will be driven low and both fault flags, FF1 and
Table 1. Fault Tabl e
Fault
No Fault
Pin
FF1 FF2
L L
Action
No Action
Latched
–
FF2, will be high impedance. V REG must rise above the turn-on
threshold, V REGUV + Δ V REGUV , before the output circuits are
activated. This ensures that the external FET is operating in its
fully enhanced state and avoids permanent damage to the FET,
caused by overheating.
VIN Undervoltage
VREG Undervoltage
Overtemperature
Open LED
Shorted LED
LED Undercurrent
Output Short
Z
Z
L
L
L
L
Z
Z
Z
Z
Z
Z
Z
L
Disable*
Disable*
No Action
Disable*
No Action
No Action
Disable*
No
No
No
Yes
No
No
Yes
The VREG Regulator is designed to operate with a typical maxi-
mum load current of 15 mA. The majority of the VREG load will
be determined by the total gate charge of the external MOSFET.
The VREG pin can be also be used as a pull-up supply for the
fault flag outputs. The current required for this function has to be
considered in the overall load calculation. Note that if FF1 is used
for driving a series protection MOSFET then only FF2 is pulled
Z
L
Disable*
Z
L
Disable*
LED Sense Resistor
Overcurrent
LED Sense Resistor
Negative Overcurrent
Shorted LED String Z L Disable*
*SG low, MOSFET off
L = active pull-down, Z = inactive, open drain
Yes
Yes
Yes
up to the VREG supply.
Overtemperature Warning If the chip temperature exceeds
the overtemperature threshold, T JF , fault flag FF2 will be high
impedance. No action will be taken by the A6268 to limit the
chip temperature. An external control circuit must take action
to avoid permanent damage to the A6268 and/or the LEDs. The
temperature will continue to be monitored and the fault flags will
11
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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