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VOUT1 + IOUT1

R

L

+

CODE

I

O(FS)

R

L

16384

(4)

VOUT2 + IOUT2

R

L

+

(16383*CODE)

I

O(FS)

R

L

16384

(5)

VOUT

(2CODE * 16383)

I

O(FS)

R

L

16384

(6)

Reference Operation

I

I

16

V

EXTIO

R

BIAS

(7)

Analog Current Outputs

DAC5675-EP

SGLS381A – OCTOBER 2006 – REVISED OCTOBER 2006

APPLICATION INFORMATION (continued)

Equation 6 shows that applying the differential output results in doubling the signal power delivered to the load.

Since the output currents IOUT1 and IOUT2 are complementary, they become additive when processed

differentially. Care should be taken not to exceed the compliance voltages at nodes IOUT1 and IOUT2, which

leads to increased signal distortion.

The DAC5675 has a bandgap reference and control amplifier for biasing the full-scale output current. The

is defined by the on-chip bandgap reference voltage and control amplifier. The full-scale output current equals

This reference can be overridden by applying an external voltage to terminal EXTIO. The bandgap reference

can additionally be used for external reference operation. In such a case, an external buffer amplifier with high

impedance input should be selected in order to limit the bandgap load current to less than 100 nA. The capacitor

Figure 21 shows a simplified schematic of the current source array output with corresponding switches.

Differential NPN switches direct the current of each individual NPN current source to either the positive output

node IOUT1 or its complementary negative output node IOUT2. The output impedance is determined by the

stack of the current sources and differential switches and is >300 k

Ω in parallel with an output capacitance

of 5 pF.

17

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