- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄375163 > AAT1239-1 (Advanced Analogic Technologies, Inc.) 40V Step-Up Converter for 4 to 10 White LEDs PDF資料下載
參數(shù)資料
| 型號： | AAT1239-1 |
| 廠商： | Advanced Analogic Technologies, Inc. |
| 英文描述： | 40V Step-Up Converter for 4 to 10 White LEDs |
| 中文描述： | 40V的升壓轉換器為4至10個白光LED |
| 文件頁數(shù)： | 11/21頁 |
| 文件大?。?/td> | 915K |
| 代理商： | AAT1239-1 |
AAT1239-1
40V Step-Up Converter for 4 to 10 White LEDs
SwitchReg
TM
PRODUCT DATASHEET
1239-1.2007.10.1.0
11
w w w . a n a l o g i c t e c h . c o m
Application Information
Over-Voltage Protection
OVP Protection with Open Circuit Failure
The OVP protection circuit consists of a resistor network
tied from the output voltage to the OVP pin (see Figure
1). To protect the device from open circuit failure, the
resistor divider can be selected such that the over-volt-
age threshold occurs prior to the output reaching 40V
(V
OUT(MAX)
). The value of R3 should be selected from 10k
Ω
to 20k
Ω
to minimize losses without degrading noise
immunity.
R
2
= R
3
·
- 1
V
OUT(MAX)
V
OVP
R2
R3
C
OUT
VOUT
AAT1239-1
OVP
GND
Figure 1: Over-Voltage Protection Circuit.
Time (4ms/div)
O
I
O
1.142V
1.238V
30
40
0
2
4
Figure 2: Over-Voltage Protection
Open Circuit Response (No LED).
Assume R3 = 12k
Ω
and V
OUT(MAX)
= 40V. Selecting 1%
resistor for high accuracy, this results in R2 = 374k
Ω
(rounded to the nearest standard value). The minimum
OVP threshold can be calculated:
·
+ 1
V
OUT(OVP_MIN)
= V
OVP(MIN)
= 35.4V
R
2
R
3
To avoid OVP detection and subsequent reduction in the
programmed output current (see following section), the
maximum operating voltage should not exceed the
minimum OVP set point.
V
OUT(MAX)
< V
OUT(OVP_MIN)
In some cases, this may disallow configurations with
high LED forward voltage (V
FLED
) and/or greater than ten
series white LEDs. V
FLED
unit-to-unit tolerance can be as
high as +15% of nominal for white LED devices.
OVP Constant Voltage Operation
Under closed loop constant current conditions, the out-
put voltage is determined by the operating current, LED
forward voltage characteristics (V
FLED
), quantity of series
connected LEDs (N), and the feedback pin voltage (V
FB
).
V
OUT
= V
FB
+ N · V
FLED
When the rising OVP threshold is exceeded, switching is
stopped and the output voltage decays. Switching auto-
matically restarts when the output drops below the
lower OVP hysteresis voltage (100mV typical) and, as a
result, the output voltage increases. The cycle repeats,
maintaining an average DC output voltage proportional
to the average of the rising and falling OVP levels (mul-
tiplied by the resistor divider scaling factor). High oper-
ating frequency and small output voltage ripple ensure
DC current and negligible flicker in the LED string(s).
The waveform in Figure 3 shows the output voltage and
LED current at cold temperature with a ten series white
LED string and V
OVP
= 40V. As shown, the output voltage
rises as a result of the increased V
FLED
which triggers the
OVP constant voltage operation. Self heating of the
LEDs triggers a smooth transition back to constant cur-
rent control.
相關PDF資料 |
PDF描述 |
|---|---|
| AAT1239ITP-1-T1 | 40V Step-Up Converter for 4 to 10 White LEDs |
| AAT1265 | Low Voltage 2MHz Step-Up DC/DC Converter in SC70JW Package |
| AAT1265IJS-3.3-T1 | Low Voltage 2MHz Step-Up DC/DC Converter in SC70JW Package |
| AAT1270 | 1A Step-Up Current Regulator for Flash LEDs |
| AAT1270IFO-T1 | 1A Step-Up Current Regulator for Flash LEDs |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AAT1239-1_08 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:40V Step-Up Converter for 4 to 10 White LEDs |
| AAT1239-1_0810 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:40V Step-Up Converter for 4 to 10 White LEDs |
| AAT1239ITP-1 | 制造商:ANALOGICTECH 制造商全稱:Advanced Analogic Technologies 功能描述:40V Step-Up Converter for 4 to 10 White LEDs |
| aat1239itp-1-db1 | 制造商:Skyworks Solutions Inc 功能描述:AAT1239 Series 40 V Step-Up Converter for 4 to 10 White LEDs Eval Board |
| AAT1239ITP-1-T1 | 制造商:Skyworks Solutions Inc 功能描述:STEP UP CONVERTER 40V FOR WLED 制造商:Skyworks Solutions Inc 功能描述:DC TO DC CONVERTER |
發(fā)布緊急采購，3分鐘左右您將得到回復。