REV. B
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AD9762
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 2000
12-Bit, 125 MSPS
TxDAC
®
D/A Converter
FUNCTIONAL BLOCK DIAGRAM
50pF
COMP1
+1.20V REF
AVDD ACOM
REFLO
COMP2
CURRENT
SOURCE
ARRAY
0.1F
+5V
SEGMENTED
SWITCHES
LSB
SWITCHES
REFIO
FS ADJ
DVDD
DCOM
CLOCK
+5V
R
SET
0.1F
CLOCK
IOUTA
IOUTB
0.1F
LATCHES
AD9762
SLEEP
DIGITAL DATA INPUTS
DB11–DB0
FEATURES
Member of Pin-Compatible TxDAC Product Family
125 MSPS Update Rate
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
APPLICATIONS
Communication Transmit Channel:
Basestations (Single/Multichannel Applications)
ADSL/HFC Modems
Direct Digital Synthesis (DDS)
Instrumentation
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 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 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.
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.
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 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.
5. The current output(s) of the AD9762 can be easily config-
ured for various single-ended or differential circuit topologies.
