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AAT2846 参数 Datasheet PDF下载

AAT2846图片预览
型号: AAT2846
PDF下载: 下载PDF文件 查看货源
内容描述: 高电流电荷泵,带有双LDO用于背光和闪光应用 [High Current Charge Pump with Dual LDO for Backlight and Flash Applications]
分类和应用:
文件页数/大小: 25 页 / 646 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
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AAT2846  
High Current Charge Pump with Dual LDO  
for Backlight and Flash Applications  
interface. The backlight section has multiple current  
address are allowed since the address is not reset  
after each write. Address edges are needed when  
changing the address, or writing to an address  
other than the default after shutdown. Address 0 is  
the default address after shutdown. If the part is  
enabled with only data edges and no address, then  
Address 0 will be programmed and backlight chan-  
nels BL1-BL6 will turn-on according to the number  
of data edges applied.  
level scales and the maximum current level is fixed at  
20mA or 30mA, depending on the scale chosen  
through programming. The flash section maximum  
current level is user programmable by an external set  
resistor. The maximum flash current that can be sup-  
ported by the device is 300mA/channel, or 600mA  
total. This corresponds to a 280K set resistor value.  
For maximum LED current lower than 300mA, use  
a programming resistor greater than 280kΩ up to  
1MΩ. Calculate the flash programming resistor  
value using the equation:  
When ENS is held low for a time greater than TOFF  
(500µs), the AAT2846 enters shutdown mode and  
draws less than 1µA of current from IN. At shut-  
down, the data and address registers are reset to 0.  
280k · 300mA  
2
RFSET  
=
Ω
AS Cwire Serial Interface Addressing  
IFMAX  
ENS  
where IFMAX is the maximum flash LED current in mA.  
Rising  
Address Edges  
Function  
If any one of the backlight or flash current sinks is  
not used, connect that current sink to OUT. The  
current controller monitors the sink voltage and, if it  
is connected to OUT, then the controller deter-  
mines that the current sink is not used or that the  
LED is shorted. In either case, the controller turns  
off the affected current sink.  
0
1
17  
18  
Backlight Current BL1-BL6  
Main Backlight Current  
BL1-BL5  
2
3
4
5
19  
20  
21  
22  
Sub Backlight Current BL6  
Low Current Backlight  
Flash Current FL1, FL2  
Independent Flash On/Off  
Control  
Maximum Backlight Current  
(Main and Sub)  
Backlight Independent  
Control  
BL3-BL6 On/Off Control  
BL1/BL2 On/Off Control  
2
AS Cwire Serial Interface  
12  
15  
29  
32  
The AAT2846 is dynamically programmable by the  
2
2
AS Cwire single-wire interface. AS Cwire records  
rising edges detected at the ENS pin to address  
2
and load the data registers. AS Cwire latches data  
Sub-2  
Sub-3  
19  
20  
or address after the ENS input has been held high  
for time TLAT (500µs). Address or data is differenti-  
ated by the number of ENS rising edges. Since the  
data registers are 4 bits each, the differentiating  
2
Table 1: AS Cwire Serial Interface Addressing.  
4
number of pulses is 2 or 16, so that Address 0 is  
Backlight Current Control (Address 0-3)  
identified by 17 rising edges, Address 1 by 18 ris-  
ing edges, Address 2 by 19 rising edges, etc. Data  
is set to any number of rising edges between 1 and  
16. A typical write protocol is a burst of ENS rising  
edges identifying a particular address, followed by  
a pause with ENS held high for the TLAT timeout  
period, then a burst of rising edges signifying data,  
and another TLAT timeout after the data has been  
sent. Once an address is set, multiple writes to that  
Use Addresses 0-3 to program all six backlight LED  
channels. All six backlight channels are pro-  
grammed to the same current level by writing  
Address 0 followed by any Data between 1 and 16.  
To program only the main channels BL1 through  
BL5, use Address 1. Similarly, use Address 2 to  
independently program subchannel BL6 only.  
12  
2846.2007.08.1.0