3

Definition of Terms

Nonlinearity: Error contributed by deviation of the DAC

transfer function from a “best fit straight line” function.

Normally expressed as a percentage of full scale range. For

range.

Resolution: Value of the LSB. For example, a unipolar

bipolar converter of N bits has a resolution of

Settling Time: Time required for the output function of the

stimulus, i.e., 0 to Full Scale.

Gain Error: Ratio of the DAC’s operational amplifier output

voltage to the nominal input voltage value.

Feedthrough Error: Error caused by capacitive coupling

terminals to ground.

Output Leakage Current: Current which appears on

terminal when all inputs are HIGH.

Detailed Description

The AD7541 is a 12-bit, monolithic, multiplying D/A converter.

A highly stable thin film R-2R resistor ladder network and

NMOS SPDT switches form the basis of the converter circuit.

CMOS level shifters provide low power TTL/CMOS

compatible operation. An external voltage or current reference

and an operational amplifier are all that is required for most

voltage output applications. A simplified equivalent circuit of

the DAC is shown on page 1, (Functional Diagram). The

NMOS SPDT switches steer the ladder leg currents between

potential. This configuration maintains a constant current in

each ladder leg independent of the input code. Converter

errors are further eliminated by using wider metal

interconnections between the major bits and the outputs. Use

of high threshold switches reduces the offset (leakage) errors

to a negligible level.

Each circuit is laser-trimmed, at the wafer level, to better

than 12-bits linearity. For the first four bits of the ladder,

special trim-tabbed geometries are used to keep the body of

the resistors, carrying the majority of the output current,

undisturbed. The resultant time stability of the trimmed

circuits is comparable to that of untrimmed units.

DIGITAL INPUTS

(Notes 2, 6)

-

-

0.8

-

0.8

V

2.4

-

-

2.4

-

V

Input Current

-

-

±1-

±1

µA

Input Coding

See Tables 1 and 2 (Note 6)

Binary/Offset Binary

Input Capacitance

(Note 6)

-

-

8

-

8

pF

POWER SUPPLY CHARACTERISTICS

Power Supply Voltage Range

Accuracy Is Not Guaranteed Over

This Range

+5 to +16

V

I+

All Digital Inputs High or Low

(Excluding Ladder Network)

-

-

2.0

-

2.5

mA

Total Power Dissipation

(Including Ladder Network)

-

20

-

-

-

mW

NOTES:

2. The digital control inputs are zener protected; however, permanent damage may occur on unconnected units under high energy electrostatic

fields. Keep unused units in conductive foam at all times.

4. Full scale range (FSR) is 10V for unipolar and

±10V for bipolar modes.

6. Guaranteed by design or characterization and not production tested.

7. Accuracy not guaranteed unless outputs at ground potential.

Electrical Specifications

PARAMETER

TEST CONDITIONS

UNITS

MIN

TYP

MAX

MIN

MAX

AD7541