®

DAC2 815

9

R

GND

DAC A

DAC B

DAC A

DAC B

R

GND

V

A

OUT

V

B

OUT

V

A

OUT

V

B

OUT

AGND

AGND

DAC2815

DAC2815

NOTE: Ideally R

= 0

Ω

GND

FIGURE 2. Recommended Ground Connections for Multiple DAC packages.

digital input code. This makes the resistance at V

(it can be driven by either a voltage or current reference).

The reference can be either positive or negative polarity with

a range of up to

±10V.

CMOS switches included in series with the ladder terminat-

ing resistor and the feedback resistor, R

FB

, compensate for

the temperature drift of the ladder switch ON resistance.

The output op amps are connected as transimpedance ampli-

fiers to convert the DAC-cell output current into an output

voltage. They have been specially designed and compen-

sated for precision and fast settling in this application.

POWER SUPPLY CONNECTIONS

The DAC2815 is specified for operation with power sup-

plies of V

L

= +5V and V

S

= either

±12V or ±15V. Even with

the V

Power supply decoupling capacitors (1

µF tantalum) should

be located close to the DAC power supply connections.

Separate digital and analog ground pins are provided to

permit separate current returns. They should be connected

together at one point. Proper layout of the two current

returns will prevent digital logic switching currents from

degrading the analog output signal. The analog ground

current is code dependent so the impedance to the system

reference ground must be kept to a minimum. Connect

DACs as shown in Figure 2 or use a ground plane to keep

ground impedance less than 0.1

Ω for less than 0.1LSB error.

–10V REFERENCE

An internal inverting amplifier (Gain = –1.0V/V) is

provided to invert the +10V reference. Connect +V

Inv In for a –10V reference at Inv Out.

OUTPUT RANGE CONNECTIONS

For a

±10V bipolar outputs connect the DAC2815 as shown

in Figure 3. Connect the MODE to logic high (+5V) for reset

to bipolar zero. With MODE connected low (GND) reset

will be to –Full-Scale.

0 To +10V Output Range

For 0 to +10V unipolar outputs connect the DAC2815 as

shown in Figure 4. Connect the MODE to logic low (GND)

for reset to unipolar zero.

0 To –10V Output Range

For 0 to –10V unipolar outputs connect the DAC2815 as

shown in Figure 5. Connect the MODE to logic low (GND)

for reset to unipolar zero.

CONNECTION TO DIGITAL BUS

DAC2815s can easily be connected to a

µprocessor bus.

Decode your address lines to derive the control signals

shown in Figure 6. Only one LATCH signal is required for

a system where all DAC2815s are updated simultaneously.

If you want to update DAC2815s independently, use sepa-

rate LATCH signals. The LATCH and WRITE signals can

be brought low simultaneously to update the DAC registers

with the same processor instruction that writes the final 8-bit

data word the DAC input registers.