DAC0807LCM datasheet(7/10 Pages) NSC

7 / 10 page

Test Circuits (Continued)

TLH5687 9

FIGURE 6 Reference Current Slew Rate Measurement (Note 7)

TLH5687 10

FIGURE 7 Positive VREF (Note 7)

TLH5687 11

FIGURE 8 Negative VREF (Note 7)

Application Hints

REFERENCE AMPLIFIER DRIVE AND COMPENSATION

The reference amplifier provides a voltage at pin 14 for con-

verting the reference voltage to a current and a turn-around

circuit or current mirror for feeding the ladder The reference

amplifier input currrent I14 must always flow into pin 14

regardless of the set-up method or reference voltage polarity

Connections for a positive voltage are shown in

Figure 7

The reference voltage source supplies the full current I14

For bipolar reference signals as in the multiplying mode

TLH5687 12

FIGURE 9 Programmable Gain Amplifier or

Digital Attenuator Circuit (Note 7)

R15 can be tied to a negative voltage corresponding to the

minimum input level It is possible to eliminate R15 with only

a small sacrifice in accuracy and temperature drift

The compensation capacitor value must be increased with

increases in R14 to maintain proper phase margin for R14

values of 1 25 and 5 kX minimum capacitor values are 15

37 and 75 pF The capacitor may be tied to either VEE or

ground but using VEE increases negative supply rejection

DAC0807LCM Datasheet(PDF) 7 Page - National Semiconductor (TI)