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ADG721 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADG721
Beschreibung CMOS Low Voltage 4 ohm Dual SPST Switches
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
ADG721 Datasheet, Funktion
Data Sheet
CMOS, Low Voltage, 4 Ω Dual SPST
Switches in 3 mm × 2 mm LFCSP
ADG721/ADG722/ADG723
FEATURES
1.8 V to 5.5 V single supply
4 Ω (max) on resistance
Low on resistance flatness
−3 dB bandwidth >200 MHz
Tiny package options
8-lead MSOP
3 mm × 2 mm LFCSP (A grade)
Fast switching times
tON, 20 ns
tOFF, 10 ns
Low power consumption (<0.1 μW)
TTL/CMOS compatible
APPLICATIONS
USB 1.1 signal switching circuits
Cell phones
PDAs
Battery-powered systems
Communication systems
Sample hold systems
Audio signal routing
Video switching
Mechanical reed relay replacement
FUNCTIONAL BLOCK DIAGRAMS
ADG721
ADG722
S1 S1
IN1
D1 D1
D2
IN2 IN2
S2
IN1
D2
S2
Figure 1.
ADG723
S1
D1
IN2
Figure 2.
IN1
D2
S2
SWITCHES SHOWN FOR
A LOGIC "0" INPUT
Figure 3.
GENERAL DESCRIPTION
The ADG721, ADG722, and ADG723 are monolithic CMOS
SPST switches. These switches are designed on an advanced
submicron process that provides low power dissipation yet gives
high switching speed, low on resistance, and low leakage
currents. The devices are packaged in both a tiny 3 mm × 2 mm
LFCSP and an MSOP, making them ideal for space-constrained
applications.
The ADG721, ADG722, and ADG723 are designed to operate
from a single 1.8 V to 5.5 V supply, making them ideal for use
in battery-powered instruments and with the new generation of
DACs and ADCs from Analog Devices, Inc.
The ADG721, ADG722, and ADG723 contain two independent
single-pole/single-throw (SPST) switches. The ADG721 and
ADG722 differ only in that both switches are normally open
and normally closed, respectively. In the ADG723, Switch 1 is
normally open and Switch 2 is normally closed.
Each switch of the ADG721, ADG722, and ADG723 conducts
equally well in both directions when on. The ADG723 exhibits
break-before-make switching action.
PRODUCT HIGHLIGHTS
1. 1.8 V to 5.5 V single-supply operation.
2. Very low RON (4 Ω max at 5 V, 10 Ω max at 3 V).
3. Low on resistance flatness.
4. −3 dB bandwidth >200 MHz.
5. Low power dissipation. CMOS construction ensures low
power dissipation.
6. 8-lead MSOP and 3 mm × 2 mm LFCSP.
Rev. E
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2004-2011 Analog Devices, Inc. All rights reserved.






ADG721 Datasheet, Funktion
ADG721/ADG722/ADG723
PIN CONFIGURATION AND PIN DESCRIPTIONS
S1 1 ADG721/ 8 VDD
D1 2 ADG722/ 7 IN1
ADG723
IN2 3 TOP VIEW 6 D2
GND 4 (Not to Scale) 5 S2
NOTES
1. EXPOSED PADDLE OF LFCSP
SHOULD BE TIED TO GROUND.
Figure 4. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
Mnemonic
Descriptions
1 S1
Source Pin 1. May be an input or an output.
2 D1
Drain Pin 1. May be an input or an output.
3 IN2
Logic Control Input for Switch S2D2.
4 GND
Ground (0 V) Reference.
5 S2
Source Pin 2. May be an input or an output.
6 D2
Drain Pin 2. May be an input or an output.
7 IN1
Logic Control Input for Switch S1D1.
8 VDD
Positive Power Supply Input.
Data Sheet
Table 5. Truth Table (ADG721/ADG722)
ADG721 In
ADG722 In
Switch Condition
0 1 Off
1 0 On
Table 6. Truth Table (ADG723)
Logic
Switch 1
0 Off
1 On
Switch 2
On
Off
Rev. E | Page 6 of 16

6 Page









ADG721 pdf, datenblatt
ADG721/ADG722/ADG723
APPLICATIONS
The ADG721/ADG722/ADG723 belong to a new family of
Analog Devices CMOS switches. This series of general-purpose
switches has improved switching times, lower on resistance, higher
bandwidths, low power consumption, and low leakage currents.
ADG721/ADG722/ADG723 SUPPLY VOLTAGES
Functionality of the ADG721/ADG722/ADG723 extends from
a 1.8 V to a 5.5 V single supply, which makes it ideal for battery-
powered instruments, where important design parameters are
power efficiency and performance.
It is important to note that the supply voltage affects the input
signal range, the on resistance, and the switching times of the part.
The typical performance characteristics and the specifications
clearly show the effects of the power supplies.
For VDD = 1.8 V, on resistance is typically 40 Ω over the
temperature range.
ON RESPONSE VS. FREQUENCY
Figure 21 illustrates the parasitic components that affect the ac
performance of CMOS switches (the switch is shown surrounded
by a box). Additional external capacitances further degrade some
aspects of performance. These capacitances affect feedthrough,
crosstalk, and system bandwidth.
S
VIN
CDS
RON
CD
D
VOUT
CLOAD RLOAD
Figure 21. Switch Represented by Equivalent Parasitic Components
The transfer function that describes the equivalent diagram of
the switch (Figure 21) is of the form (A)s, as shown in the
following equation:
( ( ) )A(s) = RT

s
s RON CDS
RON CT RT
+1
+1

where:
CT = CLOAD + CD + CDS
RT = RLOAD/(RLOAD + RON)
Data Sheet
The signal transfer characteristic is dependent on the switch
channel capacitance, CDS. This capacitance creates a frequency
zero in the numerator of the transfer function A(s). Because the
switch on resistance is small, this zero usually occurs at high
frequencies. The bandwidth is a function of the switch output
capacitance combined with CDS and the load capacitance. The
frequency pole corresponding to these capacitances appears in
the denominator of A(s).
The dominant effect of the output capacitance, CD, causes the
pole breakpoint frequency to occur first. Therefore, in order to
maximize bandwidth, a switch must have a low input and
output capacitance and low on resistance (see Figure 11).
OFF ISOLATION
Off isolation is a measure of the input signal coupled through
an off switch to the switch output. The capacitance, CDS, couples
the input signal to the output load, when the switch is off, as
shown in Figure 22.
S
VIN
CDS
CD
D
VOUT
CLOAD RLOAD
Figure 22. Off Isolation Is Affected by External Load
Resistance and Capacitance
The larger the value of CDS, the larger the value of feedthrough
produced. Figure 9 illustrates the drop in off isolation as a
function of frequency. From dc to roughly 1 MHz, the switch
shows better than −80 dB isolation. Up to frequencies of 10
MHz, the off isolation remains better than −60 dB. As the
frequency increases, more and more of the input signal is
coupled through to the output. Off isolation can be maximized
by choosing a switch with the smallest CDS possible. The values
of load resistance and capacitance also affect off isolation
because they contribute to the coefficients of the poles and
zeros in the transfer function of the switch when open.
( ) ( ( ) )A(s)
=

s
RLOAD
s RLOAD CDS
CLOAD + CD + CDS
+
1

Rev. E | Page 12 of 16

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