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參數(shù)資料
| 型號： | 8408RPFS |
| 廠商： | MAXWELL TECHNOLOGIES |
| 元件分類： | DAC |
| 英文描述： | Quad 8-Bit Multiplying CMOS D/A Converter with Memory |
| 中文描述： | PARALLEL, 8 BITS INPUT LOADING, 0.19 us SETTLING TIME, 8-BIT DAC, DFP28 |
| 封裝： | RAD PAK, LDFP-28 |
| 文件頁數(shù)： | 7/20頁 |
| 文件大?。?/td> | 472K |
| 代理商： | 8408RPFS |
M
7
All data sheets are subject to change without notice
2002 Maxwell Technologies
All rights reserved.
Quad 8-Bit Multiplying CMOS
D/A Converter with Memory
8408
08.20.02 REV 1
CIRCUIT INFORMATION
The 8408 combines four identical 8-bit CMOS DACs onto a single monolithic chip. Each DAC has its own reference
input, feedback resistor, and on-board data latches. It also features a read/write function that serves as an accessible
memory location for digital-input data words. The DAC’s three-state readback drivers place the data word back onto
the data bus.
D/A CONVERTER SECTION
Each DAC contains a highly stable, silicon-chromium, thin-film, R-2R resistor ladder network and eight pairs of current
steering switches. These switches are in series with each ladder resistor and are single-pole, double-throw NMOS
transistors; the gates of these transistors are controlled by CMOS inverters. Figure 3 shows a simplified circuit of the
R-2R resistor ladder section, and Figure 4 shows an approximate equivalent switch circuit. The current through each
resistor leg is switched between IOUT 1 and IOUT 2. This maintains a constant current in each leg, regardless of the
digital input logic states.
Each transistor switch has a finite “ON” resistance that can introduce errors to the DAC’s specified performance.
These resistances must be accounted for by making the voltage drop across each transistor equal to each other. This
is done by binarily scaling the transistor’s “ON” resistance from the most significant bit (MSB) to the least significant bit
(LSB). With 10 volts applied at the reference input, the current through the MSB switch is 0.5 mA, the next bit is 0.25
mA, etc.; this maintains a constant 10 mV drop across each switch and the converter’s accuracy is maintained. It also
results in a constant resistance appearing at the DAC’s reference input terminal; this allows the DAC to be driven by a
voltage or current source, ac or dc, of positive or negative polarity.
Shown in Figure 5 is an equivalent output circuit for DAC A. The circuit is shown with all digital inputs high. The leak-
age current source is the combination of surface and junction leakages to the substrate. The 1/256 current source rep-
resents the constant 1-bit current drain through the ladder terminating resistor. The situation is reversed with all digital
inputs low, as shown in Figure 6. The output capacitance is code dependent, and therefore, is modulated between the
low and high values.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 8408-SRF | 制造商:SPC Multicomp 功能描述:STRAIN RELIEF BUSHING KIT; Kit Contents:Installation Tool, Strain Reliefs, Storage Box, Kit Lid Label ;RoHS Compliant: NA |
| 8408-TM | 制造商:3M Electronic Products Division 功能描述:St Mm Plate, 8 Port, W/Couplings 8408-Tm 制造商:3M Electronic Products Division 功能描述:PLATE 8 PORT W/ST MULTIMODE CPLN 制造商:3M Electronic Products Division 功能描述:PLATE 8 PORT W/ST MULTIMODE COUPLING |
| 8408-TS | 制造商:3M Electronic Products Division 功能描述:3M(TM) ST SM PLATE, 8 PORT, WITH COUPLINGS 制造商:3M Electronic Products Division 功能描述:ST SM PLATE, 8 PORT, W/COUPLINGS 8408 TS 制造商:3M Electronic Products Division 功能描述:PLATE 8 PORT W/ST SINGLEMODE CPL 制造商:3M Electronic Products Division 功能描述:PLATE 8 PRT W/ST SNGLMD COUPLING |
| 8408-TWT | 制造商:Farnell / Duratool 功能描述:CABLE TIE INSTALLATION TOOL KIT; Kit Contents:100-Pcs of Beaded, 200-Pcs of Twist-Type Wire Ties, Kit Lid Label; Accessory Type:Cable Tie ;RoHS Compliant: NA |
| 8409 | 功能描述:支架與墊片 AL 1.500 M/F THRD RoHS:否 制造商:Schurter 類型:Transipillar Spacers 長度:16 m 螺紋大小:M4 外徑:10 mm 材料:Nylon with Steel 電鍍:Zinc |
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