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AS1540-BQFT 参数 Datasheet PDF下载

AS1540-BQFT图片预览
型号: AS1540-BQFT
PDF下载: 下载PDF文件 查看货源
内容描述: 8/4通道,12位I2C模拟数字转换器 [8/4-Channel, 12-Bit I2C Analog-to-Digital Converter]
分类和应用: 转换器
文件页数/大小: 20 页 / 749 K
品牌: AMSCO [ AMS(艾迈斯) ]
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AS1538/AS1540  
Data Sheet - Application Information  
Reading with Internal Reference On/Off  
The internal reference defaults to off when the AS1538/AS1540 power is on. If the reference (internal or external) is  
continuously turned on and off, a proper amount of settling time must be added before a normal conversion cycle can  
be started. The exact amount of settling time needed varies depending on the reference capacitor. For example for a  
reference capacitor of 4.7µF and considering the output impedance of the internal reference of 30Ω and the amount of  
time to fully charge the capacitor will be 1.4ms. If the reference capacitor is not fully discharged this time can be  
reduced greatly.  
Figure 29 shows the correct internal reference enable sequence before issuing the typical read sequences required for  
the mode when an internal reference is used.  
Note: Typical read sequences can be re-used once the internal reference has settled.  
Figure 29. Internal Reference Enable Sequence and Typical Read Sequence  
Internal-Reference  
Internal-Reference Enable Sequence  
Enable Settling Time  
S
1
0
0
1
0
A1 A0  
A
X
X
X
X
1
X
X
X
A
P
Wait until required settling time reached  
W
Write-Addressing Byte  
Command Byte  
Typical Mode Read Sequence  
Settled Internal Reference  
ADC Powerdown Mode  
ADC Sampling Mode  
Sr  
1
0
0
1
0
A1 A0  
A
SD C2 C1 C0  
1
PD0  
X
X
A
W
Write-Addressing Byte  
Command Byte  
Settled Internal Reference  
ADC Conversion Mode  
ADC Powerdown Mode *  
D11 D10 D9 D8 D6 ... D1 D0  
Sr  
1
0
0
1
0
A1 A0  
A
0
0
0
0
N
P
R
A
D7  
**  
Read-Addressing Byte  
2 x (8-bits +ACK/NACK  
* Dependant on powerdown selection  
bits PD0 and PD1.  
From Master to Slave  
From Slave to Master  
** To remain in HS mode, use repeated  
STARTs instead of STOPs  
Where:  
A: Acknowledge (SDA Low)  
N: Not Acknowledge (SDA High)  
S: START Condition  
P: STOP Condition  
Sr: Repeated START Condition  
W: 0 (Write)  
R: 1 (Read)  
X: Dont Care  
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Revision 1.03  
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