ADG3242 AD [Analog Devices], ADG3242 Datasheet - Page 9

• Manufacturer Part Number: ADG3242
• Description: 2.5 V/3.3 V, 2-Bit, Common Control Level Translator Bus Switch
• Manufacturer: AD [Analog Devices]

BUS SWITCH APPLICATIONS
Mixed Voltage Operation, Level Translation
Bus switches can provide an ideal solution for interfacing
between mixed voltage systems. The ADG3242 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 ADG3242 between the two
devices allows the devices to communicate easily. The bus
switch directly connects the two blocks, therefore 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
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
ADG3242
3.3V
SWITCH
INPUT
3.3V
3.3V SUPPLY
SEL = 3.3V
3.3V
CC
MICROPROCESSOR
supply. In this case,
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
the output will be limited to approximately 1.8 V, as shown
in Figure 8.
3.3 V to 1.8 V Translation
The ADG3242 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. The SEL pin is an active low control pin. SEL acti-
vates internal circuitry in the ADG3242 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 10. 3.3 V to 1.8 V Voltage Translation, SEL = 0 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
1.8V
V
V
0V
0V
OUT
OUT
ADG3242
ADG3242
SWITCH
SWITCH
INPUT
INPUT
2.5V
3.3V
3.3V SUPPLY
2.5V SUPPLY
SEL = 2.5V
SEL = 0V
2.5V
3.3V
CC
V
V
supply. In this case,
IN
IN
ADG3242
CC
.
1.8V
1.8V
CC
, the
CC
CC