DAC38RF86 datasheet(63/147 Pages) TI2

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IOUT

IOUT +

IOUT-

VDEE18N

(-1.8V)

VOUT1/2+

VOUT1/2-

100 :

Zext+

Zext-

VDDOUT18

IOUT+

IOUT-

DAC38RF86, DAC38RF96

DAC38RF87, DAC38RF97

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SLASEF4B – FEBRUARY 2017 – REVISED JULY 2017

Product Folder Links: DAC38RF86 DAC38RF96 DAC38RF87 DAC38RF97

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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 55). Differential current switches direct the current to either one of

the complimentary output nodes VOUT1/2+ or VOUT1/2-. These complementary output nodes are internal to the

device because of the integrated balun.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 55. Current Steering DAC Architecture

Referring to Figure 55, 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:

DAC38RF86 Datasheet(PDF) 63 Page - Texas Instruments