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WM2625CD 参数 Datasheet PDF下载

WM2625CD图片预览
型号: WM2625CD
PDF下载: 下载PDF文件 查看货源
内容描述: 低功耗双8位串行输入DAC [Low Power Dual 8-bit Serial Input DAC]
分类和应用:
文件页数/大小: 9 页 / 103 K
品牌: WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
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WM2625  
Production Data  
D2 D1 D0  
Independent operation, fast mode:  
Set DAC B output (fast mode):  
D15 D14 D13 D12 D11 D10 D9  
D8  
D7 D6 D5  
D4  
D4  
D3  
0
0
1
0
0
New DAC B value  
0
0
0
Set DAC A output (fast mode):  
D15 D14 D13 D12 D11 D10 D9  
D8  
D7 D6 D5  
D3  
0
D2 D1 D0  
1
1
0
0
New DAC A value  
0
0
0
APPLICATIONS INFORMATION  
LINEARITY, OFFSET, AND GAIN ERROR  
Amplifiers operating from a single supply can have positive or negative voltage offsets. With a  
positive offset, the output voltage changes on the first code transition. However, if the offset is  
negative, the output voltage may not change with the first code, depending on the magnitude of the  
offset voltage. This is because with the most negative supply rail being ground, any attempt to  
drive the output amplifier below ground will clamp the output at 0 V. The output voltage then  
remains at zero until the input code is sufficiently high to overcome the negative offset voltage,  
resulting in the transfer function shown in Figure 7.  
Output  
Voltage  
0 V  
Negative  
DAC code  
Offset  
Figure 7 Effect of Negative Offset  
This offset error, not the linearity error, produces the breakpoint. The transfer function would follow  
the dotted line if the output buffer could drive below the ground rail.  
DAC linearity is measured between zero-input code (all input bits at 0) and full-scale code (all  
inputs at 1), disregarding offset and full-scale errors. However, due to the breakpoint in the transfer  
function, single supply operation does not allow for adjustment when the offset is negative. In such  
cases, the linearity is therefore measured between full-scale and the lowest code that produces a  
positive (non-zero) output voltage.  
POWER SUPPLY DECOUPLING AND GROUNDING  
Printed circuit boards with separate analogue and digital ground planes deliver the best system  
performance. The two ground planes should be connected together at the low impedance power  
supply source. Ground currents should be managed so as to minimise voltage drops across the  
ground planes.  
A 0.1µF decoupling capacitor should be connected between the positive supply and ground pins of  
the DAC, with short leads as close as possible to the device. Use of ferrite beads may further  
isolate the system analogue supply from the digital supply.  
WOLFSON MICROELECTRONICS LTD  
PD Rev 1.0 April 2001  
8