ADG3242_15 Datasheet, PDF (12/16 Pages) Analog Devices – 2.5 V/3.3 V, 2-Bit Common Control Level Translator Bus Switch

ADG3242
BUS SWITCH APPLICATIONS
MIXED VOLTAGE OPERATION, LEVEL
TRANSLATION
Bus switches 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 translates from 3.3 V to 1.8 V,
from 2.5 V to 1.8 V, or from a bidirectional 3.3 V directly to 2.5 V.
Figure 28 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 does not have 3.3 V tolerant 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.
3.3V
3.3V
2.5V
3.3V ADC
2.5V
MICROPROCESSOR
Figure 28. Level Translation Between a 3.3 V ADC and a 2.5 V Microprocessor
3.3 V TO 2.5 V TRANSLATION
When VCC is 3.3 V (SEL = 3.3 V) and the input signal range is
0 V to VCC, the maximum output signal is clamped to within a
voltage threshold below the VCC supply. In this case, the output
is limited to 2.5 V, as shown in Figure 30. This device can be used
for translation from 2.5 V to 3.3 V devices and also between two
3.3 V devices.
3.3V
3.3V
2.5V
ADG3242
2.5V
2.5V
Figure 29. 3.3 V to 2.5 V Voltage Translation, SEL = VCC
V_OUT
2.5V
3.3V SUPPLY
SEL = 3.3V
V_IN
0V
SWITCH 3.3V
INPUT
Figure 30. 3.3 V to 2.5 V Voltage Translation, SEL = VCC
2.5 V TO 1.8 V TRANSLATION
When VCC is 2.5 V (SEL = 2.5 V) and the input signal range is
0 V to VCC, the maximum output signal is also clamped within
a voltage threshold below the VCC supply. In this case, the output
is limited to approximately 1.8 V, as shown in Figure 32.
2.5V
2.5V
ADG3242
1.8V
Figure 31. 2.5 V to 1.8 V Voltage Translation, SEL = 2.5 VCC
V_OUT
1.8V
2.5V SUPPLY
SEL = 2.5V
V_IN
0V
SWITCH 2.5V
INPUT
Figure 32. 2.5 V to 1.8 V Voltage Translation, SEL = VCC
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 activates inter-
nal circuitry in the ADG3242 that allows voltage translation
between 3.3 V devices and 1.8 V devices.
When VCC is 3.3 V and the input signal range is 0 V to VCC, the
maximum output signal is clamped to 1.8 V, as shown in Figure 34.
To do this, the SEL pin must be tied to Logic 0. If SEL is unused,
it can be tied directly to VCC.
3.3V
3.3V
ADG3242
1.8V
Figure 33. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V
V_OUT
1.8V
3.3V SUPPLY
SEL = 0V
Rev. A | Page 12 of 16
V_IN
0V
SWITCH 3.3V
INPUT
Figure 34. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V