ADG3241
Rev. B | Page 12 of 16
BUS SWITCH APPLICATIONS
MIXED VOLTAGE OPERATION, LEVEL
TRANSLATION
Bus switches can provide an ideal solution for interfacing
between mixed voltage systems. The ADG3241 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 27 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 ADG3241 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.
3.3V ADC
2.5
3.3
ADG3241
3.3
2.5V
MICROPROCESSOR
04221-027
Figure 27. Level Translation Between a 3.3 V ADC and a 2.5 V Microprocessor
3.3 V TO 2.5 V TRANSLATION
When V
CC
is 3.3 V (
SEL
= 3.3 V) and the input signal range is
0 V to V
CC
, the maximum output signal will be clamped to
within a voltage threshold below the V
CC
supply.
ADG3241
2.5V
2.5V
3.3V
2.5V
3.3
04221-028
Figure 28. 3.3 V to 2.5 V Voltage Translation,
SEL
= V
CC
In this case, the output is limited to 2.5 V, as shown in Figure 29.
This device can be used for translation from 2.5 V to 3.3 V
devices and also between two 3.3 V devices.
.5
0V
3.3V
OUT
SWITCH
OUTPUT
SWITCH
INPUT
V
IN
3.3V SUPPLY
SEL = 3.3V
04221-029
Figure 29. 3.3 V to 2.5 V Voltage Translation,
SEL
= V
CC
2.5 V TO 1.8 V TRANSLATION
When V
CC
is 2.5 V (
SEL
= 2.5 V) and the input signal range is
0 V to V
CC
, the maximum output signal is, as before, clamped to
within a voltage threshold below the V
CC
supply. In this case, the
output is limited to approximately 1.8 V, as shown in Figure 31.
ADG3241
1.8V
2.5V
2.5
04221-030
Figure 30. 2.5 V to 1.8 V Voltage Translation,
SEL
= 2.5 V
CC
1.8V
0V
2.5V
OUT
SWITCH
OUTPUT
SWITCH
INPUT
V
IN
2.5V SUPPLY
SEL = 2.5V
04221-031
Figure 31. 2.5 V to 1.8 V Voltage Translation,
SEL
= V
CC
3.3 V TO 1.8 V TRANSLATION
The ADG3241 offers the option of interfacing between a 3.3 V
device and a 1.8 V device. This is possible through the use of
the
SEL
pin. The
SEL
pin is an active low control pin.
SEL
activates internal circuitry in the ADG3241 that allows voltage
translation between 3.3 V devices and 1.8 V devices.
ADG3241
1.8V
.3
3.3
04221-032
Figure 32. 3.3 V to 1.8 V Voltage Translation,
SEL
= 0 V
When V
CC
is 3.3 V and the input signal range is 0 V to V
CC
,
the maximum output signal is clamped to 1.8 V, as shown in
Figure 32. To do this, the
SEL
pin must be tied to Logic 0. If
SEL
is unused, it should be tied directly to V
CC
.
