DAC5652A_15 Datasheet, PDF (17/26 Pages) Texas Instruments – DUAL, 10-BIT 275 MSPS DIGITAL-TO-ANALOG CONVERTER

DAC5652A
www.ti.com
SLAS535D – SEPTEMBER 2007 – REVISED AUGUST 2012
Single-Ended Configuration
Figure 20 shows the single-ended output configuration, where the output current IOUT1 flows into an equivalent
load resistance of 25 Ω. Node IOUT2 must be connected to AGND or terminated with a resistor of 25 Ω to
AGND. The nominal resistor load of 25 Ω gives a differential output swing of 1 V_PP when applying a 20-mA full-
scale output current.
IOUT1
IOUT2
R_LOAD
50 Ω
50 Ω
25 Ω
AGND
Figure 20. Driving a Doubly-Terminated 50-Ω Cable Using a Single-Ended Output
Reference Operation
Internal Reference
The DAC5652A has an on-chip reference circuit which comprises a 1.2-V bandgap reference and two control
amplifiers, one for each DAC. The full-scale output current, I_(OUTFS), of the DAC5652A is determined by the
reference voltage, V_REF, and the value of resistor R_SET. I_(OUTFS) is calculated by:
IOUTFS + 32
IREF + 32
VREF
RSET
(9)
The reference control amplifier operates as a V-to-I converter producing a reference current, I_REF, which is
determined by the ratio of V_REF and R_SET (see Equation 9). The full-scale output current, I_(OUTFS), results from
multiplying I_REF by a fixed factor of 32.
Using the internal reference, a 2-kΩ resistor value results in a full-scale output of approximately 20 mA. Resistors
with a tolerance of 1% or better should be considered. Selecting higher values, the output current can be
adjusted from 20 mA down to 2 mA. Operating the DAC5652A at lower than 20-mA output currents may be
desirable for reasons of reducing the total power consumption, improving the distortion performance, or
observing the output compliance voltage limitations for a given load condition.
It is recommended to bypass the EXTIO pin with a ceramic chip capacitor of 0.1 µF or more. The control
amplifier is internally compensated and its small signal bandwidth is approximately 300 kHz.
External Reference
The internal reference can be disabled by simply applying an external reference voltage into the EXTIO pin,
which in this case functions as an input. The use of an external reference may be considered for applications that
require higher accuracy and drift performance or to add the ability of dynamic gain control.
While a 0.1-µF capacitor is recommended to be used with the internal reference, it is optional for the external
reference operation. The reference input, EXTIO, has a high input impedance (1 MΩ) and can be driven by
various sources. Note that the voltage range of the external reference must stay within the compliance range of
the reference input.
Copyright © 2007–2012, Texas Instruments Incorporated
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