ADG3247 AD [Analog Devices], ADG3247 Datasheet - Page 9

• Manufacturer Part Number: ADG3247
• Description: 2.5 V/3.3 V, 16-Bit, 2-Port Level Translating, Bus Switch
• Manufacturer: AD [Analog Devices]

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 ADG3247 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 micro-
processor. The microprocessor may not have 3.3 V tolerant inputs;
therefore placing the ADG3247 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
to V
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. PrD
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
CC
Figure 4. Level Translation between a 3.3 V ADC
and a 2.5 V Microprocessor
, the maximum output signal will be clamped to within
CC
is 3.3 V (SEL = V
3.3V ADC
3.3V
2.5V
3.3V
2.5V
V
0V
OUT
ADG3247
3.3V
CC
SWITCH
INPUT
3.3V
) and the input signal range is 0 V
PRELIMINARY TECHNICAL DATA
CC
supply.
3.3V SUPPLY
SEL = 3.3V
3.3V
MICROPROCESSOR
V
IN
2.5V
2.5V
2.5V
2.5V
CC
CC
–9–
2.5 V to 1.8 V Translation
When 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 ADG3247 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 ADG3247 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 = 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
, the maximum output signal will, as before, be clamped
CC
CC
is 2.5 V (SEL = V
is 3.3 V and the input signal range is 0 V to V
2.5V
3.3V
1.8V
V
0V
OUT
ADG3247
ADG3247
CC
SWITCH
INPUT
2.5V
3.3V
) and the input signal range is 0 V
2.5V SUPPLY
SEL = 2.5V
2.5V
CC
V
supply.
IN
CC
ADG3247
.
1.8V
1.8V
CC
, the
CC
CC