adg3257 Analog Devices, Inc., adg3257 Datasheet - Page 6

• Manufacturer Part Number: adg3257
• Description: High Speed, 3.3 V/5 V Quad 2 1 Mux/demux 4-bit, 1 Of 2 Bus Switch
• Manufacturer: Analog Devices, Inc.

ADG3257
Symbol V
R
V
C
L
∆
L
GENERATOR
CONTROL INPUTS
PULSE
S1 @ 2 V
S1 @ 2 V
NOTES
1
2
3
OF THE PULSE GENERATOR.
PULSE GENERATOR FOR ALL PULSES:
C
R
Figure 3. Select, Enable, and Disable Times
L
T
OUTPUT
OUTPUT
1
= INCLUDES BOARD, STRAY, AND LOAD CAPACITANCES.
IS THE TERMINATION RESISTOR; SHOULD BE EQUAL TO Z
500
300
50
SWITCH INPUT
LOW
OUTPUT
Test
t
t
t
t
CC
CC
CC
PLH
PLZ
PHZ
SEL
= 5 V
, t
V
, t
, t
Table II. Switch S1 Condition
Figure 2. Propagation Delay
IN
PZL
ENABLE
PHL
PZH
Table III. Test Conditions
R
Figure 1. Load Circuit
T
3
t
t
t
PLH
PZL
PZH
10%
S1
OPEN
2 × V
GND
OPEN
DUT
V
0V
V
V
V
CC
CC
T
T
CC
V
500
300
50
CC
V
t
OUT
= 3.3 V
PHL
t
PHZ
t
DISABLE
F
< 2.5ns,
t
PLZ
C
L
2
t
R
< 2.5ns.
10%
S1
R
R
L
L
0V
V
V
V
V
V
OH
IH
T
T
OL
0V
0V
V
V
V
V
V
V
V
OUT
IH
T
CC
OL
OL
OH
OH
Unit
Ω
mV
pF
+ V
– V
OPEN
GND
2
V
CC
–6–
APPLICATIONS
Mixed Voltage Operation, Level Translation
Bus switches can be used to provide a solution for mixed voltage
systems where interfacing bidirectionally between 5 V and 3 V
devices is required. To interface between 5 V and 3.3 V buses,
an external diode is placed in series with the 5 V power supply
as shown in Figure 4.
The diode drops the internal gate voltage down to 4.3 V.
The bus switch limits the voltage present on the output to
Therefore, assuming a diode drop of 0.7 V and a V
the output voltage would be limited to 3.3 V with a logic high.
Similarly, the device could be used to translate bidirectionally
between 3.3 V to 2.5 V systems. In this case, there is no need
for an external diode. The internal V
V
Figure 4. Level Translation between 5 V and 3.3 V Devices
CC
= 3.3 V the bus switch will limit the output voltage to
MICROPROCESSOR/
Figure 5. Input Voltage to Output Voltage
3.3V CPU/DSP/
MEMORY
V
CC
3.3V
– External Diode Drop = V
V
0V
OUT
V
BE
CC
SWITCH INPUT
– 1 V = 2.3 V
3.3V TO 3.3V
V
CC
5V SUPPLY
3.3V TO 5V
= 5V
TH
5V
drop is 1 V, so with a
V
IN
5V MEMORY
TH
5V I/O
TH
of 1 V,
REV. D