Datasheet

NTS0101 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 5 — 11 August 2014 14 of 23
NXP Semiconductors
NTS0101
Dual supply translating transceiver; open drain; auto direction sensing
The gate bias voltage of the pass gate transistor (T3) is set at approximately one
threshold voltage above the V
CC
level of the low-voltage side. During a LOW-to-HIGH
transition, the output one-shot accelerates the output transition by switching on the PMOS
transistors (T1, T2). It bypasses the 10 k pull-up resistors and increases the current
drive capability. The one-shot is activated once the input transition reaches approximately
V
CCI
/2; it is de-activated approximately 50 ns after the output reaches V
CCO
/2. During the
acceleration time, the driver output resistance is between approximately 50  and 70 .
To avoid signal contention and minimize dynamic I
CC
, the user should wait for the
one-shot circuit to turn-off before applying a signal in the opposite direction. Pull-up
resistors are included in the device for DC current sourcing capability.
14.3 Input driver requirements
As the NTS0101 is a switch type translator, properties of the input driver directly effect the
output signal. The external open-drain or push-pull driver applied to an I/O determines the
static current sinking capability of the system. The max data rate, HIGH-to-LOW output
transition time (t
THL
), and propagation delay (t
PHL
), are dependent upon the output
impedance and edge-rate of the external driver. The limits provided for these parameters
in the data sheet assume a driver with output impedance below 50  is used.
14.4 Output load considerations
The maximum lumped capacitive load that can be driven is dependant upon the one-shot
pulse duration. In cases with very heavy 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 NTS0101 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 (approximately 50 ns). It ensures low impedance termination
and avoids output signal oscillations and one-shot retriggering.
14.5 Power-up
During operation, V
CC(A)
must never be higher than V
CC(B)
. However, during power-up,
V
CC(A)
 V
CC(B)
does not damage the device, so either power supply can be ramped up
first. There is no special power-up sequencing required. The NTS0101 includes circuitry
that disables all output ports when either V
CC(A)
or V
CC(B)
is switched off.
14.6 Enable and disable
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. The disable time (t
dis
with no external
load) indicates the delay between when OE goes LOW and when outputs actually
become disabled. The enable time (t
en
) indicates the amount of time the user must allow
for one one-shot circuitry to become operational after OE is taken HIGH. To ensure the
high-impedance OFF-state during power-up or power-down, pin OE should be tied to
GND through a pull-down resistor. The current-sourcing capability of the driver determines
the minimum value of the resistor.