DAC8501

11

SBAS212A

www.ti.com

TYPICAL CHARACTERISTICS: VDD = +2.7V (Cont.)

At TA = +25°C, and +VDD = +2.7V, unless otherwise noted.

THEORY OF OPERATION

DAC SECTION

The architecture consists of a string DAC followed by an

output buffer amplifier. Figure 1 shows a block diagram of the

DAC architecture.

The input coding to the DAC8501 is straight binary, so the

ideal output voltage is given by:

VV

D

OUT

REF

=•

65536

where D = decimal equivalent of the binary code that is

loaded to the DAC register; it can range from 0 to 65535.

FIGURE 1. DAC8501 Architecture.

FIGURE 2. Resistor String.

RESISTOR STRING

The resistor string section is shown in Figure 2, it is simply a

string of resistors, each of value R. The code loaded into the

DAC register determines at which node on the string the voltage

is tapped off to be fed into the output amplifier by closing one

of the switches connecting the string to the amplifier. It is

ensured monotonic because it is a string of resistors.

DAC Register

REF (+)

Resistor String

REF(–)

Output

Amplifier

GND

V

DD

V

OUT

V

FB

To Output

Amplifier

R

R

R

R

R

CODE CHANGE GLITCH

Time (2

µs/div)

Glitch Waveform (20mV/div)

(1)