OBSOLETE

AD9712B/AD9713B

REV. B

–5–

DIE LAYOUT AND METALIZATION INFORMATION

Die Dimensions . . . . . . . . . . . . . . . . . 220

× 196 × 15 (±2) mils

Pad Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

× 4 mils

Metalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aluminum

Backing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . None

Passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitride

THEORY AND APPLICATIONS

The AD9712B and AD9713B high speed digital-to-analog

converters utilize Most Significant Bit (MSB) decoding and

segmentation techniques to reduce glitch impulse and main-

tain 12-bit linearity without trimming.

As shown in the functional block diagram, the design is based

on four main subsections: the Decoder/Driver circuits, the

Transparent Latches, the Switch Network, and the Control Am-

plifier. An internal bandgap reference is also included to allow

operation with a minimum of external components.

Digital Inputs/Timing

The AD9712B employs single-ended ECL-compatible inputs

ECL midpoint reference is designed to match 10K ECL device

thresholds. On the AD9713B, a TTL translator is added at each

input; with this exception, the AD9712B and AD9713B are

identical.

decoded to 15 “thermometer code” lines. An equalizing delay is

included for the eight Least Significant Bits (LSBs) and

LATCH ENABLE. This delay minimizes data skew, and data

setup and hold times at the latch inputs; this is important when

operating the latches in the transparent mode. Without the

delay, skew caused by the decoding circuits would degrade

glitch impulse.

The latches operate in their transparent mode when LATCH

ENABLE (Pin 26) is at logic level “0.” The latches should be

used to synchronize data to the current switches by applying a

narrow LATCH ENABLE pulse with proper data setup and

hold times as shown in the Timing Diagram. An external latch

at each data input, clocked out of phase with the Latch Enable,

operates the AD9712B/AD9713B in a master slave (edge-

triggered) mode. This is the optimum way to operate the DAC

because data is always stable at the DAC input. An external

latch eases timing constraints when using the converter.

Although the AD9712B/AD9713B chip is designed to provide

isolation from digital inputs to the outputs, some coupling of

digital transitions is inevitable, especially with TTL or CMOS

inputs applied to the AD9713B. Digital feedthrough can be re-

duced by forming a low-pass filter using a (200

Ω) series resistor

in series with the capacitance of each digital input; this rolls off

the slew rate of the digital inputs.

References

As shown in the functional block diagram, the internal bandgap

reference, control amplifier, and reference input are pinned out

for maximum user flexibility when setting the reference.

When using the internal reference, REFERENCE OUT (Pin 20)

should be connected to CONTROL AMP IN (Pin 19). CON-

TROL AMP OUT (Pin 18) should be connected to REFER-

ENCE IN (Pin 17) through a 20

Ω resistor. A 0.1 µF ceramic

decoupling switching noise from the current sink base line. A

reference current cell provides feedback to the control amp by

t

– OUTPUT PROPAGATION DELAY

t

t

OUTPUT

ERROR

ERROR

BAND

t

PD

LATCH

ENABLE

t

LPW

t

S

VALID DATA

t

PD

DATA INPUTS

OUTPUT

LATCH ENABLE

Timing Diagram