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| 型号： | MAX8831EWE+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 12/28页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVR WHITE BCKLGT 16-WLP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| 拓扑： | 线性（LDO），PWM，升压（升压） |
| 输出数： | 5 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 1.8MHz ~ 2.2MHz |
| 电源电压： | 1.6 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-UFBGA，WLCSP |
| 供应商设备封装： | 16-WLP（2x2） |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 85°C |
| 其它名称： | MAX8831EWE+TDKR |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页当前第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
High-Efficiency, White LED Step-Up Converter
with I 2 C Interface in 2mm x 2mm WLP
Table 1. LED1, LED2 Programmable Current Levels and Register Values (continued)
ILED_CNTRL
REGISTER VALUE
0x26
0x27
0x28
0x29
0x2A
I LED_ (mA)
5.25
5.45
5.6
5.8
5.95
ILED_CNTRL
REGISTER VALUE
0x51
0x52
0x53
0x54
0x55
I LED_ (mA)
14
14.2
14.45
14.65
14.9
ILED_CNTRL
REGISTER VALUE
0x7C
0x7D
0x7E
0x7F
—
I LED_ (mA)
24.45
24.7
25
25.25
—
Soft-Start
From shutdown, once any LED_ is enabled through the
I 2 C interface, the IC prepares for soft-start. C COMP is
quickly pulled to 1V by an internal pullup clamp. Since
the LED_ feedback node voltage is less than the regu-
lation threshold (0.35V typ), 40μA current is sourced
from the error amplifier (Figure 1) and further charges
C COMP . Once V COMP reaches 1.25V, the step-up con-
verter starts switching at a reduced duty cycle. As
V COMP rises, the step-up converter duty cycle increas-
es. When V LED_ reaches 0.35V (typ), the error amplifier
stops sourcing current to C COMP , soft-start ends, and
the control loop achieves regulation as V LED_ settles.
The V COMP where the IC exits soft-start depends on the
5
4
3
2
1
LED3, LED4, LED5 CURRENT vs. ILED3,
ILED4, ILED5 CONTROL REGISTER VALUE
load. A 2.5V upper limit to V COMP is imposed to aid in
transient recovery and to allow maximum output for low
0
0
4
8
12
16
20
24
28
input voltages.
C COMP is discharged to GND through a 20k Ω internal
resistor whenever the step-up converter is turned off,
allowing the device to reinitiate soft-start when it is
enabled. See the Typical Operating Characteristics for
an example of soft-start operation.
Off, Shutdown, and Standby
The MAX8831 is considered OFF when V IN is below the
V UVLO threshold and V DD is below 1.6V. With V IN
above the V UVLO threshold, and with V DD low, the IC
enters the shutdown state and disables its internal ref-
erence. During shutdown, the MAX8831 holds all regis-
ters in reset, the step-up converter and all LED current
drivers are off, and supply current is reduced to 0.1μA
(typ). LX and LED1–LED5 are high impedance when
the step-up converter is off.
While the n-channel MOSFET is turned off, the step-up
regulator’s output is connected to IN through the exter-
nal inductor and Schottky diode.
With a valid supply voltage applied to V DD (greater
than 1.6V) and with V IN above V UVLO , the IC enters a
standby condition, whereby it is ready to accept I 2 C
commands. The step-up converter turns on when any
current regulator is enabled with an I 2 C command.
ILED3, ILED4, ILED5 CONTROL REGISTER VALUE (INTEGER)
Figure 3. LED3, LED4, LED5 String Current vs. ILED3, ILED4,
ILED5 Control Register Value
Open/Shorted LED Detection
The MAX8831 includes two fault-detection comparators
on each LED_ input to detect an open or shorted LED
condition. One comparator monitors LED_ voltage and
indicates an open LED_ fault when V LED_ falls below
100mV. The other comparator detects when LED_ volt-
age rises above V OUT - 0.7V, indicating a shorted LED
fault. The fault detection comparators are enabled only
when the corresponding LED_ current regulator is
enabled. Once a fault is detected, the two comparators
provide a single bit output (1 = fault, 0 = no fault) to the
STAT1 register (bits 0–4), corresponding to the appro-
priate LED regulator.
A debounce time of 16ms (typ) is applied from when a
fault condition is detected. At the end of the 16ms
debounce time, the status is latched in to the status
register and the respective current regulator is dis-
abled. If an open LED condition occurs on a current
regulator that is included in the adaptive output voltage
12
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