NTSX2102 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 2 — 11 February 2013 13 of 20
NXP Semiconductors
NTSX2102
Dual supply translating transceiver; open drain; auto direction sensing
14.3 Input driver requirements
As the NTSX2102 is a switch type translator, properties of the input driver directly affect
the output signal. The external open-drain driver applied to an I/O, determines the static
current sinking capability of the system. The maximum data rate, output transition times
(t
THL
, t
TLH
) and propagation delays (t
PHL
, t
PLH
) are dependent upon the output impedance
and edge-rate of the external driver.
14.4 Output load considerations
The maximum lumped capacitive load that can be driven is dependent upon the one-shot
pulse duration and has been tuned to 600 pF. In cases with higher capacitive loading,
there is a risk that the output does not reach the positive rail within the one-shot pulse
duration. To avoid excessive capacitive loading and to ensure correct triggering of the
one-shot, use short trace lengths and low capacitance connectors on NTSX2102 PCB
layouts. The length of the PCB trace should be such that the round-trip delay of any
reflection is within the one-shot pulse duration. Such a length ensures low impedance
termination and avoids output signal oscillations and one-shot retriggering.
14.5 Output enable (OE)
An output enable input (OE) is used to disable the device. Setting OE = LOW causes all
I/Os to assume the high-impedance OFF-state.
14.6 Power-up
When either of the supplies V
CC(n)
is at 0 V, outputs are in the high-impedance OFF-state.
One of the advantages of NTSX translators is that either V
CC(A)
or V
CC(B)
may be powered
up first. To reduce dissipation during power-up, ensure that output enable (OE) is defined.
Connect it via a pull down resistor to GND or, if the application allows, hardwired to V
CC(A)
.
If the OE pin is hardwired to V
CC(A)
, either supply can be powered up or down first. If a pull
down is used, the following sequences are recommended.
For power-up:
1. Apply power to either supply pin
2. Apply power to other supply pin
3. Enable the device by driving OE HIGH
For power down:
1. Disable the device by driving OE LOW
2. Remove power from either supply pin
3. Remove power from other supply pin
14.7 Pull-up resistors on I/O lines
Each A port I/O requires a pull-up resistor to V
CC(A)
, and each B port I/O requires a pull-up
resistor to V
CC(B)
. Choose the magnitude of the pull-up resistors to ensure that the output
voltage levels meet the application requirement.
