FXMA2102 Datasheet, PDF (5/16 Pages) Fairchild Semiconductor – Dual Supply, 2-Bit Voltage Translator / Buffer / Repeater / 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 0 V, 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/power-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 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
© 2010 Fairchild Semiconductor Corporation
FXMA2102 • Rev. 1.0.5
Figure 4. Application Circuit
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