adg3245 Analog Devices, Inc., adg3245 Datasheet - Page 9

• Manufacturer Part Number: adg3245
• Description: 2.5 V/3.3 V, 8-bit, 2-port Level Translating, Bus Switch
• Manufacturer: Analog Devices, Inc.

BUS SWITCH APPLICATIONS
Mixed Voltage Operation, Level Translation
Bus switches can be used to provide an ideal solution for inter-
facing between mixed voltage systems. The ADG3245 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.
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 toler-
ant inputs, therefore placing the ADG3245 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.
3.3 V to 2.5 V Translation
When V
0 V to V
within a voltage threshold below the V
In this case, the output will be limited to 2.5 V, as shown in
Figure 6.
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
Figure 5. 3.3 V to 2.5 V Voltage Translation, SEL = V
Figure 6. 3.3 V to 2.5 V Voltage Translation, SEL = V
Figure 4. Level Translation between a 3.3 V ADC
and a 2.5 V Microprocessor
CC
CC
3.3V ADC
is 3.3 V (SEL = 3.3 V) and the input signal range is
, the maximum output signal will be clamped to
3.3V
2.5V
3.3V
2.5V
V
0V
OUT
ADG3245
3.3V
SWITCH
INPUT
3.3V
3.3V SUPPLY
SEL = 3.3V
3.3V
CC
MICROPROCESSOR
supply.
V
IN
2.5V
2.5V
2.5V
2.5V
CC
CC
–9–
2.5 V to 1.8 V Translation
When V
0 V to V
to within a voltage threshold below the V
In this case, the output will be limited to approximately
1.8 V, as shown in Figure 7.
3.3 V to 1.8 V Translation
The ADG3245 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.
SEL pin: An active low control pin. SEL activates internal
circuitry in the ADG3245 that allows voltage translation
between 3.3 V devices and 1.8 V devices.
When V
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 V
Figure 7. 2.5 V to 1.8 V Voltage Translation, SEL = 2.5 V
Figure 8. 2.5 V to 1.8 V Voltage Translation, SEL = V
Figure 9. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V
CC
CC
CC
, the maximum output signal will, as before, be clamped
is 2.5 V (SEL = 2.5 V) and the input signal range is
is 3.3 V and the input signal range is 0 V to V
2.5V
3.3V
1.8V
V
0V
OUT
ADG3245
ADG3245
SWITCH
INPUT
3.3V
2.5V
2.5V SUPPLY
SEL = 2.5V
2.5V
CC
V
supply.
IN
ADG3245
CC
.
1.8V
1.8V
CC
, the
CC
CC