AD ADG3246BRU

2.5 V/3.3 V, 10-Bit, 2-Port
Level Translating, Bus Switch
ADG3246
FEATURES
225 ps Propagation Delay through the Switch
4.5 Switch Connection between Ports
Data Rate 1.244 Gbps
2.5 V/3.3 V Supply Operation
Selectable Level Shifting/Translation
Small Signal Bandwidth 610 MHz
Level Translation
3.3 V to 2.5 V
3.3 V to 1.8 V
2.5 V to 1.8 V
24-Lead TSSOP and LFCSP Packages
FUNCTIONAL BLOCK DIAGRAM
APPLICATIONS
3.3 V to 1.8 V Voltage Translation
3.3 V to 2.5 V Voltage Translation
2.5 V to 1.8 V Voltage Translation
Bus Switching
Bus Isolation
Hot Swap
Hot Plug
Analog Signal Switching
A0
B0
A9
B9
BE
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The ADG3246 is a 2.5 V or 3.3 V, 10-bit, 2-port digital switch.
It is designed on Analog Devices’ low voltage CMOS process,
which provides low power dissipation yet gives high switching
speed and very low on resistance, allowing inputs to be connected
to outputs without additional propagation delay or generating
additional ground bounce noise.
1.
2.
3.
4.
5.
3.3 V or 2.5 V supply operation
Extremely low propagation delay through switch
4.5 W switches connect inputs to outputs
Level/voltage translation
24-lead 4 mm ¥ 4 mm LFCSP and 24-lead TSSOP packages
The switches are enabled by means of the bus enable (BE)
input signal. These digital switches allow bidirectional signals to
be switched when ON. In the OFF condition, signal levels up to
the supplies are blocked.
This device is ideal for applications requiring level translation.
When operated from a 3.3 V supply, level translation from 3.3 V
inputs to 2.5 V outputs occurs. Similarly, if the device is operated from a 2.5 V supply and 2.5 V inputs are applied, the device
will translate the outputs to 1.8 V. In addition to this, the ADG3246
has a level translating select pin (SEL). When SEL is low, VCC is
reduced internally, allowing for level translation between 3.3 V
inputs and 1.8 V outputs. This makes the device suited to applications requiring level translation between different supplies,
such as converter to DSP/microcontroller interfacing.
REV. 0
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. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
ADG3246–SPECIFICATIONS1
Parameter
DC ELECTRICAL CHARACTERISTICS
Input High Voltage
Input Low Voltage
Input Leakage Current
OFF State Leakage Current
ON State Leakage Current
Maximum Pass Voltage
CAPACITANCE3
A Port Off Capacitance
B Port Off Capacitance
A, B Port On Capacitance
Control Input Capacitance
Symbol
Conditions
Min
VINH
VINH
VINL
VINL
II
IOZ
VCC = 2.7 V to 3.6 V
VCC = 2.3 V to 2.7 V
VCC = 2.7 V to 3.6 V
VCC = 2.3 V to 2.7 V
2.0
1.7
VP
0 £ A, B £ VCC
0 £ A, B £ VCC
VA/VB = VCC = SEL = 3.3 V, IO = –5 mA
VA/VB = VCC = SEL = 2.5 V, IO = –5 mA
VA/VB = VCC = 3.3 V, SEL = 0 V, IO = –5 mA
CA OFF
CB OFF
CA, CB ON
CIN
f = 1 MHz
f = 1 MHz
f = 1 MHz
f = 1 MHz
tPHL, tPLH
CL = 50 pF, VCC = SEL = 3 V
tPZH, tPZL
tPHZ, tPLZ
tPZH, tPZL
tPHZ, tPLZ
tPZH, tPZL
tPHZ, tPLZ
VCC = 3.0 V to 3.6 V; SEL = VCC
VCC = 3.0 V to 3.6 V; SEL = VCC
VCC = 3.0 V to 3.6 V; SEL = 0 V
VCC = 3.0 V tp 3.6 V; SEL = 0 V
VCC = 2.3 V to 2.7 V; SEL = VCC
VCC = 2.3 V to 2.7 V; SEL = VCC
VCC = SEL = 3.3 V; VA/VB = 2 V
VCC = SEL = 3.3 V; VA/VB = 2 V
SWITCHING CHARACTERISTICS3
Propagation Delay A to B or B to A, tPD4
Propagation Delay Matching5
Bus Enable Time BE to A or B6
Bus Disable Time BE to A or B6
Bus Enable Time BE to A or B6
Bus Disable Time BE to A or B6
Bus Enable Time BE to A or B6
Bus Disable Time BE to A or B6
Maximum Data Rate
Channel Jitter
Operating Frequency—Bus Enable
fBE
DIGITAL SWITCH
On Resistance
RON
On Resistance Matching
POWER REQUIREMENTS
VCC
Quiescent Power Supply Current
Increase in ICC per Input7
(VCC = 2.3 V to 3.6 V, GND = 0 V, all specifications TMIN to TMAX, unless
otherwise noted.)
⌬RON
2.0
1.5
1.5
B Version
Typ2
± 0.01
± 0.01
± 0.01
2.5
1.8
1.8
Unit
0.8
0.7
±1
±1
±1
2.9
2.1
2.1
V
V
V
V
mA
mA
mA
V
V
V
5
5
10
6
1
1
0.5
0.5
0.5
0.5
3.2
3.2
2.2
1.7
2.2
1.75
1.244
50
pF
pF
pF
pF
0.225
22.5
4.8
4.8
3.3
2.9
3
2.6
10
VCC = 3 V, SEL = VCC, VA = 0 V, IBA = 8 mA
VCC = 3 V, SEL = VCC, VA = 1.7 V, IBA = 8 mA
VCC = 2.3 V, SEL = VCC, VA = 0 V, IBA = 8 mA
VCC = 2.3 V, SEL = VCC, VA = 1 V, IBA = 8 mA
VCC = 3 V, SEL = 0 V, VA = 0 V, IBA = 8 mA
VCC = 3 V, SEL = 0 V, VA = 1 V, IBA = 8 mA
VCC = 3 V, SEL = VCC, VA = 0 V, IBA = 8 mA
VCC = 3 V, SEL = VCC, VA = 1 V, IBA = 8 mA
4.5
15
5
11
5
14
0.45
0.65
2.3
ICC
ICC
⌬ICC
Max
Digital Inputs = 0 V or VCC; SEL = VCC
Digital Inputs = 0 V or VCC; SEL = 0 V
VCC = 3.6 V, BE = 3.0 V; SEL = VCC
0.001
0.65
ns
ps
ns
ns
ns
ns
ns
ns
Gbps
ps p-p
MHz
8
28
9
18
8
W
W
W
W
W
W
W
W
3.6
1
1.2
130
V
mA
mA
mA
NOTES
1
Temperature range is as follows: B Version: –40∞C to +85∞C.
2
Typical values are at 25∞C, unless otherwise stated.
3
Guaranteed by design, not subject to production test.
4
The digital switch contributes no propagation delay other than the RC delay of the typical R ON of the switch and the load capacitance when driven by an ideal voltage
source. Since the time constant is much smaller than the rise/fall times of typical driving signals, it adds very little propagation delay to the system. Propagation delay
of the digital switch when used in a system is determined by the driving circuit on the driving side of the switch and its interaction with the load on the driven side.
5
Propagation delay matching between channels is calculated from the on resistance matching and load capacitance of 50 pF.
6
See Timing Measurement Information section.
7
This current applies to the control pin (BE) only. The A and B ports contribute no significant ac or dc currents as they transition.
Specifications subject to change without notice.
–2–
REV. 0
ADG3246
LFCSP Package
␪JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . . 35°C/W
TSSOP Package
␪JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . 128°C/W
Lead Temperature, Soldering (10 seconds) . . . . . . . . . . 300°C
IR Reflow, Peak Temperature (<20 seconds) . . . . . . . . 235°C
ABSOLUTE MAXIMUM RATINGS*
(TA = 25°C, unless otherwise noted.)
VCC to GND . . . . . . . . . . . . . . . . . . . . . . . . . –0.5 V to +4.6 V
Digital Inputs to GND . . . . . . . . . . . . . . . . . –0.5 V to +4.6 V
DC Input Voltage . . . . . . . . . . . . . . . . . . . . . –0.5 V to +4.6 V
DC Output Current . . . . . . . . . . . . . . . . . . 25 mA per channel
Operating Temperature Range
Industrial (B Version) . . . . . . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
*Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability. Only one absolute
maximum rating may be applied at any one time.
ORDERING GUIDE
Model
Temperature Range
Package Description
Package Option
ADG3246BCP
ADG3246BCP-REEL7
ADG3246BRU
ADG3246BRU-REEL7
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Lead Frame Chip Scale Package (LFCSP)
Lead Frame Chip Scale Package (LFCSP)
Thin Shrink Small Outline Package (TSSOP)
Thin Shrink Small Outline Package (TSSOP)
CP-24
CP-24
RU-24
RU-24
Table I. Pin Description
Table II. Truth Table
Mnemonic
Description
BE
SEL*
Function
BE
SEL
Ax
Bx
Bus Enable (Active Low)
Level Translation Select
Port A, Inputs or Outputs
Port B, Inputs or Outputs
L
L
H
L
H
X
A = B, 3.3 V to 1.8 V Level Shifting
A = B, 3.3 V to 2.5 V/2.5 V to 1.8 V Level Shifting
Disconnect
*SEL = 0 only when V DD = 3.3 V ± 10%
24 A4
23 A3
22 A2
21 A1
20 A0
19 V CC
PIN CONFIGURATION
24-Lead LFCSP and TSSOP
PIN 1
INDICATOR
ADG3246
TOP VIEW
18 BE
17 B0
16 B1
15 B2
14 B3
13 B4
1
24
VCC
A0 2
23
BE
A1 3
22
B0
A2 4
21
B1
A3 5
20
B2
ADG3246
A4 6
TOP VIEW 19 B3
A5 7 (Not to Scale) 18 B4
GND 7
B9 8
B8 9
B7 10
B6 11
B5 12
SEL 1
A5 2
A6 3
A7 4
A8 5
A9 6
SEL
A6 8
17
B5
A7 9
16
B6
A8 10
15
B7
A9 11
14
B8
GND 12
13
B9
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
ADG3246 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.
REV. 0
–3–
ADG3246
TERMINOLOGY
VCC
Positive Power Supply Voltage.
GND
Ground (0 V) Reference.
VINH
Minimum Input Voltage for Logic 1.
VINL
Maximum Input Voltage for Logic 0.
II
Input Leakage Current at the Control Inputs.
IOZ
OFF State Leakage Current. It is the maximum leakage current at the switch pin in the OFF state.
IOL
ON State Leakage Current. It is the maximum leakage current at the switch pin in the ON state.
VP
Maximum Pass Voltage. The maximum pass voltage relates to the clipped output voltage of an NMOS device
when the switch input voltage is equal to the supply voltage.
RON
Ohmic Resistance Offered by a Switch in the ON State. It is measured at a given voltage by forcing a specified
amount of current through the switch.
⌬RON
On Resistance Match between Any Two Channels, i.e., RON Max – RON Min.
CX OFF
OFF Switch Capacitance.
CX ON
ON Switch Capacitance.
CIN
Control Input Capacitance. This consists of BE and SEL.
ICC
Quiescent Power Supply Current. It is measured when all control inputs are at a logic HIGH or LOW level and
the switches are OFF.
⌬ICC
Extra power supply current component for the BE control input when the input is not criven at the supplies.
tPLH, tPHL
Data Propagation Delay through the Switch in the ON State. Propagation delay is related to the RC time constant
RON ¥ CL, where CL is the load capacitance.
tPZH, tPZL
Bus Enable Times. These are times taken to cross the VT voltage at the switch output when the switch turns on in
response to the control signal, BE.
tPHZ, tPLZ
Bus Disable Times. This is the time taken to place the switch in the high impedance OFF state in response to the control
signal. It is measured as the time taken for the output voltage to change by V⌬ from the original quiescent level,
with reference to the logic level transition at the control input. (Refer to Figure 3 for enable and disable times.)
Max Data Rate
Maximum Rate at which Data Can Be Passed through the Switch.
Channel Jitter
Peak-to-Peak Value of the Sum of the Deterministic and Random Jitter of the Switch Channel.
fBE
Operating Frequency of Bus Enable. This is the maximum frequency at which bus enable (BE) can be toggled.
–4–
REV. 0
Typical Performance Characteristics–ADG3246
40
40
VCC = 3V
TA = 25C
SEL = VCC
35
35
30
30
VCC = 3.3V
20
RON – 25
25
VCC = 2.5V
20
15
VCC = 3V
TA = 25C
SEL = 0V
35
30
RON – RON – 40
VCC = 2.3V
TA = 25C
SEL = VCC
25
VCC = 3.3V
20
15
15
VCC = 3.6V
VCC = 2.7V
10
VCC = 3.6V
5
0
0
0.5
1.0
2.0
1.5
VA/VB – V
3.0
2.5
10
10
5
5
0
3.5
0
0
TPC 1. On Resistance vs.
Input Voltage
1.0
0.5
2.0
1.5
VA/VB – V
2.5
3.0
0
1.0
1.5
2.0
VA/VB – V
3.0
15
VCC = 3.3V
3.0
3.5
SEL = VCC
VCC = 3.6V
TA = 25C
SEL = VCC
IO = –5A
VCC = 2.5V
SEL = VCC
2.5
TPC 3. On Resistance vs.
Input Voltage
TPC 2. On Resistance vs.
Input Voltage
20
0.5
2.5
10
85C
10
VOUT – V
RON – RON – 15
85C
VCC = 3.3V
VCC = 3V
1.5
1.0
5
5
2.0
40C
25C
25C
0.5
40C
0
0
1.0
VA/VB – V
0.5
0
2.0
1.5
TPC 4. On Resistance vs. Input
Voltage for Different Temperatures
0.5
VA/VB – V
1.0
1.2
TPC 5. On Resistance vs. Input
Voltage for Different Temperatures
2.5
0
0.5
1.0
2.0
1.5
VCC – V
2.5
3.0
3.5
TPC 6. Pass Voltage vs. VCC
1800
2.5
TA = 25C
SEL = VCC
IO = –5A
2.0
TA = 25C
SEL = 0V
IO = –5A
VCC = 2.7V
2.0
VCC = 3.6V
TA = 25C
1600
1400
VCC = 2.5V
VCC = 2.3V
1.0
1.5
VCC = 3.3V
VCC = 3V
1.0
ICC – A
1200
1.5
VOUT – V
VOUT – V
0
0
VCC = 3.3V, SEL = 0V
1000
800
600
0.5
VCC = SEL = 3.3V
400
0.5
VCC = SEL = 2.5V
200
0
0
0.5
1.0
1.5
2.0
VCC – V
2.5
TPC 7. Pass Voltage vs. VCC
REV. 0
3.0
0
0
0.5
1.0
1.5
2.0
VCC – V
2.5
3.0
TPC 8. Pass Voltage vs. VCC
–5–
3.5
0
0
2
4
6
8 10 12 14 16 18 20
ENABLE FREQUENCY – MHz
TPC 9. ICC vs. Enable Frequency
ADG3246
3.0
3.0
TA = 25C
VA = 0V
BE = 0
2.5
1.5
VCC = SEL = 3.3V
1.0 V = SEL = 2.5V
CC
0.5
0.5
0.02
0.04
0.06
IO – A
0.08
TPC 10. Output Low Characteristic
–0.06
–0.04
IO – A
–0.02
0
0
–6
–8
–10
–12
–40
–50
–30
–60
–70
0.03
0.1
1
10
100
FREQUENCY – MHz
–50
–90
–100
0.1
1
10
100
FREQUENCY – MHz
1000
90
2.0
ENABLE
DISABLE
TIME – ns
TIME – ns
ENABLE
2.0
80
VCC = SEL = 2.5V
2.5
VCC = 3.3V, SEL = 0V
1.5
0.03
0.1
1
10
100
FREQUENCY – MHz
1000
VCC = SEL = 3.3V
VIN = 2V p-p
20dB ATTENUATION
70
DISABLE
JITTER – ps
DISABLE
TA = 25C
VCC = 3.3V/2.5V
SEL = V CC
VIN = 0dBm
N/W ANALYZER:
RL = RS = 50
100
2.5
VCC = SEL = 3.3V
3.0
TPC 15. Off Isolation vs.
Frequency
TPC 14. Crosstalk vs. Frequency
ENABLE
3.0
2.5
–70
–90
0.03
3.5
1.5
2.0
VA/VB – V
–60
–80
1000
TPC 13. Bandwidth vs. Frequency
–40
–80
–100
–14
1.0
TPC 12. Charge Injection vs.
Source Voltage
ATTENUATION – dB
–4
0.5
–20
TA = 25C
VCC = 3.3V/2.5V
SEL = V CC
ADJACENT CHANNELS
VIN = 0dBm
N/W ANALYZER:
RL = RS = 50
–30
ATTENUATION – dB
ATTENUATION – dB
–2.0
–0.08
–20
TA = 25C
VCC = 3.3V/2.5V
SEL = V CC
VIN = 0dBm
N/W ANALYZER:
RL = RS = 50
VCC = 3.3V
–1.8
TPC 11. Output High Characteristic
0
–2
–1.0
–1.2
–1.6
0
–0.10
0.10
VCC = 2.5V
–0.8
–1.4
VCC = 3.3V; SEL = 0V
VCC = SEL = 2.5V
0
–0.6
1.5
1.0
0
SEL = VCC
ON OFF
CL = InF
–0.4
VCC = SEL = 3.3V
2.0
VCC = 3.3V; SEL = 0V
VOUT – V
VOUT – V
2.0
TA = 25C
–0.2
QINJ – pC
2.5
0
TA = 25C
VA = VCC
BE = 0
1.5
1.0
60
50
40
30
1.0
20
0.5
0.5
10
0
–40
–20
0
20
40
60
TEMPERATURE – C
80
100
TPC 16. Enable/Disable Time
vs. Temperature
0
–40
–20
0
20
40
60
TEMPERATURE – C
80
100
TPC 17. Enable/Disable Time
vs. Temperature
–6–
0
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
DATA RATE – Gbps
TPC 18. Jitter vs. Data Rate;
PRBS 31
REV. 0
ADG3246
100
95
VCC = SEL = 3.3V
VIN = 2V p-p
20dB ATTENUATION
EYE WIDTH – %
90
85
80
75
70
65
35mV/DIV
100ps/DIV
60
% EYE WIDTH = ((CLOCK PERIOD –
JITTER p-p)/CLOCK PERIOD) 100%
55
VCC = 3.3V
SEL = 3.3V
VIN = 2V p-p
20dB
ATTENUATION
TA = 25C
37mV/DIV
200ps/DIV
VCC = 2.5V
SEL = 2.5V
VIN = 2V p-p
20dB
ATTENUATION
TA = 25C
50
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
DATA RATE – Gbps
TPC 19. Eye Width vs. Data
Rate; PRBS 31
50.1mV/DIV
50ps/DIV
TA = 25C
TPC 20. Eye Pattern; 1.244
Gbps, VCC = 3.3 V, PRBS 31
20dB
ATTENUATION
VCC = 3.3V
SEL = 3.3V
VIN = 2V p-p
TPC 22. Jitter @ 1.244 Gbps,
PRBS 31
REV. 0
–7–
TPC 21. Eye Pattern; 1 Gbps,
VCC = 2.5 V, PRBS 31
ADG3246
TIMING MEASUREMENT INFORMATION
For the following load circuit and waveforms, the notation that is used is VIN and VOUT where
VIN = VA and VOUT = VB or VIN = VB and VOUT = VA
VIH
VCC
2 VCC
SW1
PULSE
GENERATOR
VT
tPLH
GND
RL
VOUT
VIN
CONTROL
INPUT BE
tPHL
VH
VT
VOUT
VL
D.U.T.
Figure 2. Propagation Delay
RL
CL
RT
0V
NOTES
PULSE GENERATOR FOR ALL PULSES: tR ⱕ 2.5ns, tF ⱕ 2.5ns,
FREQUENCY ⱕ 10MHz.
CL INCLUDES BOARD, STRAY, AND LOAD CAPACITANCES.
RT IS THE TERMINATION RESISTOR, SHOULD BE EQUAL TO ZOUT
OF THE PULSE GENERATOR.
Figure 1. Load Circuit
Test Conditions
Symbol
VCC = 3.3 V ± 0.3 V (SEL = VCC)
VCC = 2.5 V ± 0.2 V (SEL = VCC)
VCC = 3.3 V ± 0.3 V (SEL = 0 V)
Unit
RL
VD
CL
VT
500
300
50
1.5
500
150
30
0.9
500
150
30
0.9
W
mV
pF
V
DISABLE
ENABLE
VINH
VT
CONTROL INPUT BE
0V
tPZL
VIN = 0V
VOUT
SW1 @ 2VCC
tPLZ
VCC
VL + V
VL
TEST
S1
VH
tPLZ, tPZL
tPHZ, tPZH
2 ¥ VCC
GND
tPZH
VIN = VCC
VOUT
SW1 @ GND
Table III. Switch Position
VCC
VT
tPHZ
VT
0V
VH – V
0V
Figure 3. Enable and Disable Times
–8–
REV. 0
ADG3246
2.5 V to 1.8 V Translation
BUS SWITCH APPLICATIONS
Mixed Voltage Operation, Level Translation
When VCC is 2.5 V (SEL = VCC) and the input signal range is 0 V
to VCC, the maximum output signal will, as before, be clamped
to within a voltage threshold below the VCC supply.
Bus switches can be used to provide an ideal solution for interfacing between mixed voltage systems. The ADG3246 is suitable
for applications where voltage translation from 3.3 V technology to
a lower voltage technology is needed. This device can translate
from 3.3 V to 1.8 V, from 2.5 V to 1.8 V, or bidirectionally
from 3.3 V directly to 2.5 V.
2.5V
3.3V
3.3V
2.5V
3.3V ADC
ADG3246
Figure 4 shows a block diagram of a typical application in which
a user needs to interface between a 3.3 V ADC and a 2.5 V microprocessor. The microprocessor may not have 3.3 V tolerant inputs,
therefore placing the ADG3246 between the two devices allows
the devices to communicate easily. The bus switch directly
connects the two blocks, thus introducing minimal propagation
delay, timing skew, or noise.
2.5V
MICROPROCESSOR
ADG3246
2.5V
1.8V
Figure 7. 2.5 V to 1.8 V Voltage Translation, SEL = VCC
In this case, the output will be limited to approximately 1.8 V,
as shown in Figure 7.
VOUT
2.5V SUPPLY
SEL = 2.5V
SWITCH
OUTPUT
1.8V
Figure 4. Level Translation between a 3.3 V ADC
and a 2.5 V Microprocessor
3.3 V to 2.5 V Translation
0V
When VCC is 3.3 V (SEL = VCC) and the input signal range is 0 V
to VCC, the maximum output signal will be clamped to within a
voltage threshold below the VCC supply.
SWITCH
INPUT
VIN
2.5V
Figure 8. 2.5 V to 1.8 V Voltage Translation, SEL = VCC
3.3 V to 1.8 V Translation
The ADG3246 offers the option of interfacing between a 3.3 V
device and a 1.8 V device. This is possible through use of the
SEL pin.
3.3V
3.3V
SEL pin: An active low control pin. SEL activates internal circuitry in the ADG3246 that allows voltage translation between
3.3 V devices and 1.8 V devices.
2.5V
ADG3246
2.5V
2.5V
3.3V
Figure 5. 3.3 V to 2.5 V Voltage Translation, SEL = VCC
In this case, the output will be limited to 2.5 V, as shown in
Figure 6.
VOUT
3.3V
ADG3246
1.8V
3.3V SUPPLY
SEL = 3.3V
2.5V
SWITCH
OUTPUT
Figure 9. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V
0V
SWITCH
INPUT
When VCC is 3.3 V and the input signal range is 0 V to VCC, the
maximum output signal will be clamped to 1.8 V, as shown in
Figure 9. To do this, the SEL pin must be tied to Logic 0. If
SEL is unused, it should be tied directly to VCC.
VIN
3.3V
Figure 6. 3.3 V to 2.5 V Voltage Translation, SEL = VCC
This device can be used for translation from 2.5 V to 3.3 V
devices and also between two 3.3 V devices.
REV. 0
–9–
VOUT
3.3V SUPPLY
SEL = 0V
1.8V
SWITCH
OUTPUT
CPU
0V
RAM
SWITCH
INPUT
VIN
3.3V
ADG3246 ADG3246
ADG3246
PLUG-IN
CARD (1)
CARD I/O
PLUG-IN
CARD (2)
CARD I/O
Figure 10. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V
Bus Isolation
A common requirement of bus architectures is low capacitance
loading of the bus. Such systems require bus bridge devices that
extend the number of loads on the bus without exceeding the
specifications. Because the ADG3246 is designed specifically for
applications that do not need drive yet require simple logic functions, it solves this requirement. The device isolates access to the
bus, thus minimizing capacitance loading.
LOAD A
LOAD C
Analog Switching
BUS/
BACKPLANE
BUS SWITCH
LOCATION
LOAD B
Figure 12. ADG3246 in a Hot Plug Application
There are many systems that require the ability to handle hot
swapping, such as docking stations, PCI boards for servers, and
line cards for telecommunications switches. If the bus can be
isolated prior to insertion or removal, then there is more control
over the hot swap event. This isolation can be achieved using a
bus switch. The bus switches are positioned on the hot swap card
between the connector and the devices. During hot swap, the
ground pin of the hot swap card must connect to the ground pin
of the back plane before any other signal or power pins.
Bus switches can be used in many analog switching applications;
for example, video graphics. Bus switches can have lower on
resistance, smaller ON and OFF channel capacitance and thus
improved frequency performance than their analog counterparts.
The bus switch channel itself consisting solely of an NMOS
switch limits the operating voltage (see TPC 1 for a typical plot),
but in many cases, this does not present an issue.
LOAD D
Figure 11. Location of Bus Switched in a Bus
Isolation Application
Hot Plug and Hot Swap Isolation
The ADG3246 is suitable for hot swap and hot plug applications.
The output signal of the ADG3246 is limited to a voltage that is
below the VCC supply, as shown in Figures 6, 8, and 10. Therefore the switch acts like a buffer to take the impact from hot
insertion, protecting vital and expensive chipsets from damage.
In hot-plug applications, the system cannot be shutdown when
new hardware is being added. To overcome this, a bus switch
can be positioned on the backplane between the bus devices and
the hot plug connectors. The bus switch is turned off during hot
plug. Figure 12 shows a typical example of this type of application.
High Impedance During Power-Up/Power-Down
To ensure the high impedance state during power-up or powerdown, BE should be tied to VCC through a pull-up resistor; the
minimum value of the resistor is determined by the currentsinking capability of the driver.
PACKAGE AND PINOUT
The ADG3246 is packaged in both a small 24-lead TSSOP or a
tiny 24-lead LFCSP package. The area of the TSSOP option is
49.375 mm2, while the area of the LFCSP option is 16 mm2. This
leads to a 67% savings in board space when using the LFCSP package compared with the TSSOP package. This makes the LFCSP
option an excellent choice for space-constrained applications.
The ADG3246 in the TSSOP package offers a flowthrough
pinout. The term flowthrough signifies that all the inputs are on
opposite sides from the outputs. A flowthrough pinout simplifies
the PCB layout.
–10–
REV. 0
ADG3246
OUTLINE DIMENSIONS
24-Lead Lead Frame Chip Scale Package [LFCSP]
4 mm 4 mm Body
(CP-24)
Dimensions shown in millimeters
0.60 MAX
4.0
BSC SQ
PIN 1
INDICATOR
0.25
MIN
0.60 MAX
TOP
VIEW
BOTTOM
VIEW
0.50
0.40
0.30
1.00
0.90
0.85
24
19
18
0.50
BSC
3.75
BSC SQ
13
12
7
2.25
1.70 SQ
0.75
6
2.50
REF
0.80 MAX
0.65 NOM
12 MAX
PIN 1
INDICATOR
1
0.05 MAX
0.02 NOM
0.25
REF
0.30
0.23
0.18
SEATING
PLANE
0.20 REF
COPLANARITY
0.08
COMPLIANT TO JEDEC STANDARDS MO-220-VGGD-2
24-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-24)
Dimensions shown in millimeters
7.90
7.80
7.70
24
13
4.50
4.40
4.30
6.40 BSC
1
12
PIN 1
0.65
BSC
0.15
0.05
0.30
0.19
0.10 COPLANARITY
1.20
MAX
SEATING
PLANE
0.20
0.09
8
0
COMPLIANT TO JEDEC STANDARDS MS-153AD
REV. 0
–11–
0.75
0.60
0.45
–12–
C03012–0–5/03(0)