REV. B
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.
a
AD9708
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., 1999
8-Bit, 100 MSPS+
TxDAC
®
D/A Converter
FUNCTIONAL BLOCK DIAGRAM
+1.20V REF
REFLO
REF IO
FS ADJ
50pF
COMP1
0.1mF
CURRENT
SOURCE
ARRAY
+5V
AVDD
SEGMENTED
SWITCHES
LATCHES
DIGITAL DATA INPUTS (DB7–DB0)
DVDD
DCOM
CLOCK
SLEEP
IOUTA
IOUTB
COMP2
ACOM
0.1mF
+5V
R
SET
CLOCK
0.1mF
AD9708
FEATURES
Member of Pin-Compatible TxDAC Product Family
125 MSPS Update Rate
8-Bit Resolution
Linearity: 1/4 LSB DNL
Linearity: 1/4 LSB INL
Differential Current Outputs
SINAD @ 5 MHz Output: 50 dB
Power Dissipation: 175 mW @ 5 V to 45 mW @ 3 V
Power-Down Mode: 20 mW @ 5 V
On-Chip 1.20 V Reference
Single +5 V or +3 V Supply Operation
Packages: 28-Lead SOIC and 28-Lead TSSOP
Edge-Triggered Latches
Fast Settling: 35 ns Full-Scale Settling to 0.1%
APPLICATIONS
Communications
Signal Reconstruction
Instrumentation
PRODUCT DESCRIPTION
The AD9708 is the 8-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, was 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 AD9708 offers exceptional ac and dc performance
while supporting update rates up to 125 MSPS.
The AD9708’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 45 mW, without a significant degradation in
performance, by lowering the full-scale current output. In addi-
tion, a power-down mode reduces the standby power dissipa-
tion to approximately 20 mW.
The AD9708 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 temperature compensated bandgap reference have been inte-
grated to provide a complete monolithic DAC solution. Flexible
supply options support +3 V and +5 V CMOS logic families.
The AD9708 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. The current outputs may be
directly tied to an output resistor to provide two complemen-
tary, single-ended voltage outputs. The output voltage compliance
range is 1.25 V.
The AD9708 contains a 1.2 V on-chip reference and reference
control amplifier, which allows the full-scale output current to
be simply set by a single resistor. The AD9708 can be driven by
a variety of external reference voltages. The AD9708’s full-scale
current can be adjusted over a 2 mA to 20 mA range without
any degradation in dynamic performance. Thus, the AD9708
may operate at reduced power levels or be adjusted over a 20 dB
range to provide additional gain ranging capabilities.
The AD9708 is available in 28-lead SOIC and 28-lead TSSOP
packages. It is specified for operation over the industrial tem-
perature range.
PRODUCT HIGHLIGHTS
1. The AD9708 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 AD9708 uses a pro-
prietary switching technique that enhances dynamic perfor-
mance well beyond 8- and 10-bit video DACs.
3. On-chip, edge-triggered input CMOS latches readily interface
to +3 V and +5 V CMOS logic families. The AD9708 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 allows the AD9708 to operate at reduced power levels
(i.e., 45 mW) without any degradation in dynamic performance.
5. A temperature compensated, 1.20 V bandgap reference is
included on-chip providing a complete DAC solution. An
external reference may be used.
6. The current output(s) of the AD9708 can easily be config-
ured for various single-ended or differential applications.
