
ADG3308/ADG3308-1
Data Sheet
Rev. D | Page 16 of 20
THEORY OF OPERATION
shifting necessary for data transfer in a system where multiple
supply voltages are used. The device requires two supplies, VCCA
and VCCY (VCCA ≤ VCCY). These supplies set the logic levels on
each side of the device. When driving the A pins, the device
translates the VCCA compatible logic levels to VCCY compatible
logic levels available at the Y pins. Similarly, because the device
is capable of bidirectional translation, when driving the Y pins
the VCCY compatible logic levels are translated to the VCCA
compatible logic levels available at the A pins. When EN = 0,
the A1 pin to the A8 pin and the Y1 pin to the Y8 pin are three-
into normal operation mode and perform level translation.
LEVEL TRANSLATOR ARCHITECTURE
channels. Each channel can translate logic levels in either the
A→Y or the Y→A direction. They use a one-shot accelerator
architecture, ensuring excellent switching characteristics.
Figure 39 shows a simplified block diagram of a bidirectional
channel.
ONE-SHOT GENERATOR
6k
Y
VCCA
VCCY
T2
T1
T3
T4
A
P
N
U1
U2
U4
U3
04865-
053
Figure 39. Simplified Block Diagram of an
The logic level translation in the A→Y direction is performed
using a level translator (U1) and an inverter (U2), whereas the
translation in the Y→A direction is performed using the U3
inverter and U4 inverter. The one-shot generator detects a rising
or falling edge present on either the A side or the Y side of the
channel. It sends a short pulse that turns on the PMOS transistors
(T1 and T2) for a rising edge, or the NMOS transistors (T3 and
T4) for a falling edge. This charges/discharges the capacitive load
faster, resulting in fast rise and fall times.
The inputs of the unused channels (A or Y) should be tied to
their corresponding VCC rail (VCCA or VCCY) or to GND.
INPUT DRIVING REQUIREMENTS
the circuit that drives the input of the device should be able
to ensure rise/fall times of less than 3 ns when driving a
load consisting of a 6 k resistor in parallel with the input
OUTPUT LOAD REQUIREMENTS
drive CMOS-compatible loads. If current-driving capability
is required, it is recommended to use buffers between the
ENABLE OPERATION
A I/O pins and the Y I/O pins by using the enable (EN) pin, as
Table 4. Truth Table
EN
Y I/O Pins
A I/O Pins
0
High-Z1
1
Normal operation2
1
High impedance state.
2
mode. In this mode, the current consumption from both the
VCCA and VCCY supplies is reduced, allowing the user to save
power, which is critical, especially in battery-operated systems.
The EN input pin can only be driven with VCCY compatible logic
with either VCCA- or VCCY compatible logic levels.
POWER SUPPLIES
For proper operation of the device, the voltage applied to the
VCCA must always be less than or equal to the voltage applied
to VCCY. To meet this condition, the recommended power-up
operate properly only after both supply voltages reach their
nominal values. It is not recommended to use the part in a system
where, during power-up, VCCA may be greater than VCCY due to
a significant increase in the current taken from the VCCA supply.
For optimum performance, the VCCA and VCCY pins should be
decoupled to GND as close as possible to the device.