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2014-01-0006 PT0474-1 02/18/14
7
PI4ULS3V302
140Mb/s Bi-directional Level Translator
for Push-Pull Applications
Functional Description
The PI4ULS3V302 is a 2-bit configurable dual-supply autosensing bidirectional level translator that does not require a
direction control pin. The B and A ports are designed to track two different power supply rails, VCCB and VCCA respectively.
The PI4ULS3V302 offers the feature that the values of the VCCB and V
CCA
supplies are independent. Design flexibility is
maximized because VCCA can be set to a value either greater than or less than the VCCB supply.
The PI4ULS3V302 has high output current capability, which allows the translator to drive high capacitive loads such as most
high frequency EMI filters. Another feature of the PI4ULS3V302 is that each An and Bn channel can function as either an input or
an output.
An Output Enable (EN) input is available to reduce the power consumption. The EN pin can be used to disable both I/O ports
by putting them in 3-state which significantly reduces the supply current.
Application Information
Level Translator Architecture
The PI4ULS3V302 auto-sense translator provides bi-directional logic voltage level shifting to transfer data in multiple supply
voltage systems. These level translators have two supply voltages, V
CCA
and V
CCB
, which set the logic levels on the input and
output sides of the translator. When used to transfer data from the I/O V
CCA
to the I/O V
CCB
ports, input signals referenced to the
V
CCA
supply are translated to output signals with a logic level matched to VCCB. In a similar manner, the I/O V
CCB
to I/O V
CCA
translation shifts input signals with a logic level compatible to V
CCB
to an output signal matched to V
CCA
. The PI4ULS3V302
translator consists of bi-directional channels that independently determine the direction of the data flow without requiring a
directional pin. One-shot circuits are used to detect the rising or falling input signals. In addition, the one-shots decrease the rise
and fall times of the output signal for high-to-low and low-to-high transitions.
Input Driver Requirements
Auto-sense translators such as the PI4ULS3V302 have a wide bandwidth, but a relatively small DC output current rating. The
high bandwidth of the bi-directional I/O circuit is used to quickly transform from an input to an output driver and vice versa. The
I/O ports have a modest DC current output specification so that the output driver can be over driven when data is sent in the
opposite direction. For proper operation, the input driver to the auto-sense translator should be capable of driving 3mA of peak
output current. The bi-directional configuration of the translator results in both input stages being active for a very short time
period. Although the peak current from the input signal circuit is relatively large, the average current is small and consistent with a
standard CMOS input stage. Enable Input (EN) The PI4ULS3V302 translator has an Enable pin (EN) that provides tri−state
operation at the I/O pins. Driving the Enable pin to a low logic level minimizes the power consumption of the device and drives
the I/O V
CCB
and I/O V
CCA
pins to a high impedance state. Normal translation operation occurs when the EN pin is equal to a logic
high signal. The EN pin is referenced to the V
CCA
supply and has Over-Voltage Tolerant (OVT) protection.
Uni-Directional versus Bi-Directional Translation
The PI4ULS3V302 translator can function as a non-inverting uni-directional translator. One advantage of using the translator as
a uni-directional device is that each I/O pin can be configured as either an input or output. The configurable input or output feature
is especially useful in applications such as SPI that use multiple uni-directional I/O lines to send data to and from a device. The
flexible I/O port of the auto sense translator simplifies the trace connections on the PCB.
