12-Bit, 125 MSPS
®
a
TxDAC D/A Converter
AD9762*
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Member of Pin-Compatible TxDAC Product Family
125 MSPS Update Rate
+5V
0.1F
12-Bit Resolution
Excellent Spurious Free Dynamic Range Performance
SFDR to Nyquist @ 5 MHz Output: 70 dBc
Differential Current Outputs: 2 mA to 20 mA
Power Dissipation: 175 mW @ 5 V to 45 mW @ 3 V
Power-Down Mode: 25 mW @ 5 V
On-Chip 1.20 V Reference
Single +5 V or +3 V Supply Operation
Package: 28-Lead SOIC and TSSOP
Edge-Triggered Latches
REFLO
+1.20V REF
COMP1
AVDD ACOM
AD9762
50pF
0.1F
REFIO
0.1F
CURRENT
COMP2
SOURCE
FS ADJ
ARRAY
R
SET
+5V
DVDD
DCOM
IOUTA
IOUTB
SEGMENTED
SWITCHES
LSB
SWITCHES
CLOCK
SLEEP
CLOCK
LATCHES
APPLICATIONS
DIGITAL DATA INPUTS (DB11–DB0)
Communication Transmit Channel:
Basestations (Single/Multichannel Applications)
ADSL/HFC Modems
Direct Digital Synthesis (DDS)
Instrumentation
Differential current outputs are provided to support single-
ended or differential applications. Matching between the two
current outputs ensures enhanced dynamic performance in a
differential output configuration. The current outputs may be
tied directly to an output resistor to provide two complemen-
tary, single-ended voltage outputs or fed directly into a trans-
former. The output voltage compliance range is 1.25 V.
PRODUCT DESCRIPTION
The AD9762 is the 12-bit resolution member of the TxDAC
series of high performance, low power CMOS digital-to-analog
converters (DACs). The TxDAC family which consists of pin
compatible 8-, 10-, 12-, and 14-bit DACs is specifically opti-
mized for the transmit signal path of communication systems.
All of the devices share the same interface options, small outline
package and pinout, thus providing an upward or downward
component selection path based on performance, resolution and
cost. The AD9762 offers exceptional ac and dc performance
while supporting update rates up to 125 MSPS.
The on-chip reference and control amplifier are configured for
maximum accuracy and flexibility. The AD9762 can be driven
by the on-chip reference or by a variety of external reference
voltages. The internal control amplifier which provides a wide
(>10:1) adjustment span allows the AD9762 full-scale current
to be adjusted over a 2 mA to 20 mA range while maintaining
excellent dynamic performance. Thus, the AD9762 may oper-
ate at reduced power levels or be adjusted over a 20 dB range to
provide additional gain ranging capabilities.
The AD9762’s flexible single-supply operating range of 2.7 V to
5.5 V and low power dissipation are well suited for portable and
low power applications. Its power dissipation can be further
reduced to a mere 45 mW without a significant degradation in
performance by lowering the full-scale current output. Also, a
power-down mode reduces the standby power dissipation to
approximately 25 mW.
The AD9762 is available in 28-lead SOIC and TSSOP pack-
ages. It is specified for operation over the industrial tempera-
ture range.
PRODUCT HIGHLIGHTS
1. The AD9762 is a member of the TxDAC product family which
provides an upward or downward component selection path
based on resolution (8 to 14 bits), performance and cost.
2. Manufactured on a CMOS process, the AD9762 uses a pro-
prietary switching technique that enhances dynamic perfor-
mance beyond what was previously attainable by higher
power/cost bipolar or BiCMOS devices.
3. On-chip, edge-triggered input CMOS latches interface readily
to +3 V and +5 V CMOS logic families. The AD9762 can
support update rates up to 125 MSPS.
4. A flexible single-supply operating range of 2.7 V to 5.5 V and
a wide full-scale current adjustment span of 2 mA to 20 mA
allow the AD9762 to operate at reduced power levels.
The AD9762 is manufactured on an advanced CMOS process.
A segmented current source architecture is combined with a
proprietary switching technique to reduce spurious components
and enhance dynamic performance. Edge-triggered input
latches and a 1.2 V temperature compensated bandgap refer-
ence have been integrated to provide a complete monolithic
DAC solution. Flexible supply options support +3 V and +5 V
CMOS logic families.
The AD9762 is a current-output DAC with a nominal full-scale
output current of 20 mA and > 100 kΩ output impedance.
TxDAC is a registered trademark of Analog Devices, Inc.
*Patent pending.
REV. B
5. The current output(s) of the AD9762 can be easily config-
ured for various single-ended or differential circuit topologies.
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 2000