DAC38RF80 datasheet(73/155 Pages) TI1

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IOUT

IOUT +

IOUT-

VDEE18N

(-1.8V)

VOUT1/2+

VOUT1/2-

100 :

Zext+

Zext-

VDDOUT18

IOUT+

IOUT-

DAC38RF80, DAC38RF83, DAC38RF84

DAC38RF85, DAC38RF90, DAC38RF93

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SLASEA3C – DECEMBER 2016 – REVISED JULY 2017

DAC38RF83 DAC38RF93

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Table 40. DAC output current (continued)

DACFS ( 8.5.72)

Signal current (mA)

Total bias current (mA)(1)

An external decoupling capacitor CEXT of 0.1 μF should be connected externally to terminal EXTIO for

compensation. RBIAS of 3.6 kΩ is recommended for setting the full-scale output current.

8.3.28 Current Steering DAC Architecture

The DACs in the DAC38RFxx consist of a segmented array of NMOS current sources, capable of sinking a full-

scale output current up to 40 mA (see Figure 71). Differential current switches direct the current to either one of

the complimentary output nodes VOUT1/2+ or VOUT1/2-. On the DAC38RF80/90/84 with integrated balun, these

output nodes are internal to the device. Complimentary output currents enable differential operation, thus

canceling out common mode noise sources (digital feed-through, on-chip and PCB noise), dc offsets, even order

distortion components, and increasing signal output power by a factor of four.

Figure 71. Current Steering DAC Architecture

Referring to Figure 71, the total output current IOUTFS is fixed, and is switched to either the + or – output by

switches S(N):

(11)

Since the output stage is a current sinking architecture, we will denote current into the DAC as + current, and the

current flows IOUT+ and IOUT- into terminals VOUT1/2+ and VOUT1/2- respectively. IOUT+ and IOUT- can be

expressed as:

DAC38RF80 Datasheet(PDF) 73 Page - Texas Instruments