ADG3242

Rev. A | Page 12 of 16

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 ADC

2.5V

3.3V

2.5V

MICROPROCESSOR

3.3V

Figure 28. Level Translation Between a 3.3 V ADC and a 2.5 V Microprocessor

3.3 V TO 2.5 V TRANSLATION

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.

ADG3242

2.5V

2.5V

3.3V

2.5V

3.3V

2.5V

0V

3.3V

SWITCH

INPUT

3.3V SUPPLY

SEL = 3.3V

2.5 V TO 1.8 V TRANSLATION

is limited to approximately 1.8 V, as shown in Figure 32.

ADG3242

1.8V

2.5V

2.5V

1.8V

0V

2.5V

SWITCH

INPUT

2.5V SUPPLY

SEL = 2.5V

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.

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,

ADG3242

1.8V

3.3V

3.3V

Figure 33. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V

1.8V

0V

3.3V

SWITCH

INPUT

3.3V SUPPLY

SEL = 0V

Figure 34. 3.3 V to 1.8 V Voltage Translation, SEL = 0 V