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DAC5687 View Datasheet(PDF) - Texas Instruments

Part NameDescriptionManufacturer
DAC5687 16-BIT, 500 MSPS 2?8 INTERPOLATING DUAL-CHANNEL DIGITAL-TO-ANALOG CONVERTER (DAC) Texas-Instruments
Texas Instruments Texas-Instruments
DAC5687 Datasheet PDF : 80 Pages
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fINPUT
Ref
CDC7005
#1
DAC5687
SLWS164E – FEBRUARY 2005 – REVISED SEPTEMBER 2006
Y0
CLK1
Y0
fINPUT
CLK1C
Y1
Y1
fDAC
CLK2
CLK2C
Y2
CLK1
Y2
fINPUT
CLK1C
Y3
Y3
fDAC
CLK2
CLK2C
DAC5687
#1
DAC5687
#2
Ref
CDC7005
#2
Y0
CLK1
Y0
fINPUT
CLK1C
Y1
Y1
fDAC
CLK2
CLK2C
Y2
CLK1
Y2
fINPUT
CLK1C
Y3
Y3
fDAC
CLK2
CLK2C
DAC5687
#3
DAC5687
#4
B0170-01
Figure 58. Block Diagram for Clock Synchronization of Multiple DAC5687 Devices in Dual-Clock Mode
Reference Operation
The DAC5687 comprises a band-gap reference and control amplifier for biasing the full-scale output current. The
full-scale output current is set by applying an external resistor RBIAS to pin BIASJ. The bias current IBIAS through
resistor RBIAS is defined by the on-chip band-gap reference voltage and control amplifier. The full-scale output
current equals 16 times this bias current. The full-scale output current IOUTFS can thus be expressed as:
IOUTFS = 16 × IBIAS = 16 × VEXTIO / RBIAS
where VEXTIO is the voltage at terminal EXTIO. The band-gap reference voltage delivers an accurate voltage of
1.2 V. This reference is active when terminal EXTLO is connected to AGND. An external decoupling capacitor
CEXT of 0.1 µF should be connected externally to terminal EXTIO for compensation. The band-gap reference can
additionally be used for external reference operation. In that case, an external buffer with high-impedance input
should be applied in order to limit the band-gap load current to a maximum of 100 nA. The internal reference can
be disabled and overridden by an external reference by connecting EXTLO to AVDD. Capacitor CEXT may hence
be omitted. Terminal EXTIO thus serves as either input or output node.
The full-scale output current can be adjusted from 20 mA down to 2 mA by varying resistor RBIAS or changing the
externally applied reference voltage. The internal control amplifier has a wide input range, supporting the
full-scale output current range of 20 mA.
DAC Transfer Function
The CMOS DACs consist of a segmented array of NMOS current sinks, capable of sinking a full-scale output
current up to 20 mA. Differential current switches direct the current of each current source through either one of
the complementary output nodes IOUT1 or IOUT2. Complementary output currents enable differential operation,
thus canceling out common-mode noise sources (digital feedthrough, on-chip and PCB noise), dc offsets,
even-order distortion components, and increasing signal output power by a factor of two.
Copyright © 2005–2006, Texas Instruments Incorporated
Product Folder Link(s): DAC5687
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