REV. 0

ADG3246

–9–

BUS SWITCH APPLICATIONS

Mixed Voltage Operation, Level Translation

Bus switches can be used to provide an ideal solution for interfac-

ing between mixed voltage systems. The ADG3246 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 ADG3246 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

2.5V

3.3V

2.5V

MICROPROCESSOR

3.3V

Figure 4. Level Translation between a 3.3 V ADC

and a 2.5 V Microprocessor

3.3 V to 2.5 V Translation

ADG3246

2.5V

2.5V

3.3V

2.5V

3.3V

Figure 5. 3.3 V to 2.5 V Voltage Translation,

SEL = V

CC

In this case, the output will be limited to 2.5 V, as shown in

Figure 6.

2.5V

0V

3.3V

SWITCH

INPUT

3.3V SUPPLY

SEL = 3.3V

Figure 6. 3.3 V to 2.5 V Voltage Translation,

SEL = V

CC

This device can be used for translation from 2.5 V to 3.3 V

devices and also between two 3.3 V devices.

2.5 V to 1.8 V Translation

ADG3246

1.8V

2.5V

2.5V

Figure 7. 2.5 V to 1.8 V Voltage Translation,

SEL = V

CC

In this case, the output will be limited to approximately 1.8 V,

as shown in Figure 7.

1.8V

0V

2.5V

SWITCH

INPUT

2.5V SUPPLY

SEL = 2.5V

Figure 8. 2.5 V to 1.8 V Voltage Translation,

SEL = V

CC

3.3 V to 1.8 V Translation

The ADG3246 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 cir-

cuitry in the ADG3246 that allows voltage translation between

3.3 V devices and 1.8 V devices.

ADG3246

1.8V

3.3V

3.3V

Figure 9. 3.3 V to 1.8 V Voltage Translation,

SEL = 0 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