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AAT3174 参数 Datasheet PDF下载

AAT3174图片预览
型号: AAT3174
PDF下载: 下载PDF文件 查看货源
内容描述: 大电流,高效率电荷泵 [High Current, High Efficiency Charge Pump]
分类和应用:
文件页数/大小: 14 页 / 272 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
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AAT3174  
High Current, High Efficiency Charge Pump  
For examples of standard 1% values where the  
LED flash current level is targeted for 700mA, see  
Table 3.  
Next, choose a reasonable value for R1. A value  
that is slightly larger than RSET, calculated from  
above, is appropriate. Calculate R2 and then calcu-  
late the torch mode current level that results:  
R1  
R2  
ILED  
ILED  
Ω
Ω
(k )  
(k )  
Torch (mA) Flash (mA)  
RSET · R1  
920  
732  
649  
562  
193  
205  
210  
223  
122  
153  
173  
200  
703  
701  
707  
703  
R2 =  
R1 - RSET  
R - R  
2
VIO  
1
ILED (torch) = 600mA · 187kΩ ·  
-
R1 · R2 0.7V · R2⎠  
Table 3: Open-Drain I/O Example  
Resistor Values.  
If the I/O port must be configured as an open-drain  
PMOS type output, the appropriate equations can  
be generated from these same concepts. As done  
in the previous example, the necessary values can  
then be calculated.  
Once again, the current and resistance values used  
in the equations come from the conditions placed on  
the IDX parameter of the Electrical Characteristics  
table. 0.7V is the typical value for the VRSET param-  
eter. The value to use for VIO must come from the  
I/O supply voltage used in the system.  
As a reference, the equations applicable to the  
PMOS case are:  
Example standard 1% values are provided in Table 4.  
R1  
R2  
ILED  
ILED  
600mA · 187kΩ  
ILED (flash)  
(kΩ)  
(kΩ)  
Torch (mA) Flash (mA)  
R1 =  
169  
165  
162  
160  
1000  
1000  
1000  
1000  
95  
776  
792  
805  
813  
111  
124  
132  
VIO  
- 1  
0.7  
R2 =  
1
ILED (torch)  
-
Table 4: Push-Pull I/O Example  
Resistor Values.  
R1 600mA · 187kΩ  
In all of the approaches mentioned, the open-drain  
NMOS or PMOS type configurations offer the most  
flexibility for current level selection.  
The value to use for VIO must come from the I/O  
supply voltage used in the system. 0.7V is the typ-  
ical value of the VRSET parameter found in the  
Electrical Characteristics.  
When configured as an output, if the I/O port is only  
push-pull type, then the equivalent open-drain  
NMOS can also be realized. To realize this, acti-  
vate the port as output only when driving the line  
low. Otherwise, to release the line, set the port to  
be tri-stated.  
For a push-pull I/O port output configuration, first  
calculate the overall RSET value needed for the  
desired flash level LED current:  
600mA · 187kΩ  
ILED (flash)  
RSET  
=
3174.2006.05.1.2  
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