FXMAR2102 Datasheet, PDF (5/16 Pages) Fairchild Semiconductor – Dual-Supply, 2-Bit Voltage Translator / Isolator for I2C Applications

Functional Description
Power-Up / Power-Down Sequencing
FXM translators offer an advantage in that either V_CC
may be powered up first. This benefit derives from the
chip design. When either V_CC is at 0V, outputs are in a
high-impedance state. The control input (OE) is
designed to track the V_CCA supply. A pull-down resistor
tying OE to GND should be used to ensure that bus
contention, excessive currents, or oscillations do not
occur during power-up/-down. The size of the pull-down
resistor is based upon the current-sinking capability of
the device driving the OE pin.
The recommended power-up sequence is:
1. Apply power to the first V_CC.
2. Apply power to the second V_CC.
3. Drive the OE input HIGH to enable the device.
The recommended power-down sequence is:
1. Drive OE input LOW to disable the device.
2. Remove power from either V_CC.
3. Remove power from the other V_CC.
Note:
4. Alternatively, the OE pin can be hardwired to V_CCA
to save GPIO pins. If OE is hardwired to V_CCA,
either V_CC can be powered up or down first.
Application Circuit
Figure 4. Application Circuit
© 2011 Fairchild Semiconductor Corporation
FXMAR2102 • Rev. 1.0.0
5
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