TCA9617B Datasheet, PDF (11/24 Pages) Texas Instruments – Level-Translating FM+ I2C Bus Repeater

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TCA9617B
SCPS259A – DECEMBER 2014 – REVISED DECEMBER 2014
Feature Description (continued)
9.3.3 High to Low Transition Characteristics
When the A side of the bus is driven to 0.7 V_CCA, the B side driver will turn on. This will drive the B-side to 0 V for
a short period (see Figure 8) and then the B-side will rise to the static offset voltage of 0.5 V (V_OL of TCA9617B).
This effect, called an inverted pedestal, allows the B-side to drive to logic low much faster than driving to the
static offset. Driving to the static offset voltage requires that the fall time be slowed to prevent ringing.
9^th Clock Pulse – Acknowledge
SCL
SDA
Figure 7. Bus A (0.8 V to 5.5 V Bus) Waveform
Inverted Pedestal
SCL
9^th Clock Pulse – Acknowledge
Pedestal
SDA
V_OL of TCA9617B
V_OL of Slave
Figure 8. Bus B (2.2 V to 5.5 V Bus) Waveform
GND
9.4 Device Functional Modes
The TCA9617B has an active-high enable (EN) input with an internal pull-up to V_CCB, which allows the user to
select when the repeater is active. This can be used to isolate a badly behaved slave on power-up reset. It
should never change state during an I²C operation, because disabling during a bus operation may hang the bus,
and enabling part way through the bus cycles could confuse the I²C parts being enabled. The EN input should
change state only when the global bus and repeater port are in the idle state to prevent system failures.
INPUT
EN
L
H
Table 1. Function Table
FUNCTION
Outputs disabled
SDAA = SDAB
SCLA = SCLB
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