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DAC5687 数据手册 - TI（德州仪器）
制造商:
TI（德州仪器）
封装:
HTQFP-100
描述:
16 位 500 MSPS 2x-8x 内插双通道数模转换器 (DAC)
Pictures:
3D模型
符号图
焊盘图
引脚图
产品图
页面导航:
引脚图在P33Hot
典型应用电路图在P65
原理图在P2P20P21P22P23P36P39P51P65
封装尺寸在P74P75P76
焊盘布局在P65
型号编码规则在P1
封装信息在P74P75P76
技术参数、封装参数在P5P6P7P8P9P10P20
应用领域在P1P74P79
电气规格在P6P7P8P9P10P20
导航目录
DAC5687数据手册
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IOUT1
4:1
IOUT2
100 Ω
100 Ω
R
LOAD
50 Ω
AVDD (3.3 V)
AVDD (3.3 V)
S0033-02
Combined Output Termination
S0069-01
IOUTA1
1:1
R
LOAD
50 Ω
IOUTA2
AVDD (3.3 V)
IOUTB1
IOUTB2
DAC5687
SLWS164E – FEBRUARY 2005 – REVISED SEPTEMBER 2006
Figure 61. Driving a Doubly Terminated 50- Ω Cable Using a 4:1 Impedance Ratio Transformer
The DAC5687 DAC A and DAC B outputs can be summed together as shown in Figure 62 to provide a 40-mA
full-scale output for increased output power.
Figure 62. Combined Output Termination Using a 1:1 Impedance Ratio Transformer Into 50- Ω Load
For the case where the digital codes for the two DACs are identical, the termination results in a full-scale swing
of 2 V
PP
into the 50- Ω load, or 10 dBm. This is 6 dB higher than the 4:1 output termination recommended for a
single DAC output.
There are two methods to produce identical DAC codes. In modes where there is mixing between digital
channels A and B, i.e., when channels A and B are isolated, the identical data can be sent to both input ports to
produce identical DAC codes. Channels A and B are isolated when FMIX is disabled, the QMC is disabled or
enabled with QMC phase register set to 0, and CMIX is disabled or set to f
DAC
/2. Note that frequency
upconversion is still possible using the high-pass filter setting and CMIX f
DAC
/2.
Alternatively, by applying the input data on one input port only and setting the other input port to midscale (zero),
the NCO can be used to duplicate the output of the active input channel in the other channel by setting the
frequency to zero, phase to 8192 and NCO_GAIN = 1 and QMC gain = 1446. Assuming I(t) is the wanted signal
and Q(t) = 0, this is demonstrated by the simplification of the NCO equations in the Fine Mixer (FMIX) section:
I
OUT
(t) = (I
IN
(t)cos(2 π × 0 × t + π /4) – 0 × sin(2 π × 0 × t + π /4) × 2
(1 – 1)
= I
IN
(t)cos( π /4) = I
IN
(t)/2
½
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