Application Note TLE7250 About this document Z8F54978220

Application Note

Z8F54978220

Pin Description

5 Pin Description

5.1

V

CC

Pin

The V

CC

pin supplies the transmitter output stage. The transmitter operates according to data sheet specifications in the voltage range of 4.5 V < V

CC

< 5.5 V. Voltage V then the transmitter is disabled. The undervoltage threshold V

CC

> 6 V can damage the device. If V

CC_UV

CC

< V

CC_UV

is in the range from 3.65 V to 4.3 V. If

V

CC_UV

< V

CC

< 4.5 V, then the transmitter is enabled and can then send data to the bus, but parameters may be outside the specified range.

,

5.2

NEN and NRM Pins

The NEN pin and the NRM set the mode of TLE7250 and are usually directly connected to output ports of a microcontroller. If the mode pins are unconnected and TLE7250 is supplied by V

CC

, then the device enters

Power-save mode, due to the internal pull-up resistor to V

CC via the NEN and NRM pins, assuming V

IO

> V

IO_UV

on NEN and NRM. Table 3 shows mode changes

. Features and modes of operation are described in

Chapter 2 .

Table 3 Mode Selection via NEN and NRM

Mode of Operation

Power-Save mode

NEN

“high”

NRM

“high” “X”

Receive-Only mode

Normal-Operating mode

Comment

If NEN is set to “high”, then the device enters Power-save mode, independent of the logical input at NRM.

“low” “low” Transmitter is disabled. The receiver is enabled and operates as specified in the data sheet.

“low” “high” If V

CC

> V

CC_UV

, then the transmitter is enabled.

Power-save mode is the low-power mode of TLE7250. In Power-save mode both the transmitter and the receiver are disabled and current consumption is reduced to a minimum. The user can deactivate the transmitter of TLE7250 either by setting the NEN pin to “high” or setting the NRM pin to “low”. This can be used to implement two different fail safe paths.

For disconnected mode pins or microcontroller ports in “tristate” the TLE7250 has an integrated pull-up resistor to V

CC

, by default the device is in Power-save mode in order to enable low current consumption.

5.3

TxD Pin

TxD is an input pin. TxD pin is used to receive the data stream from the microcontroller. If V

IO

> V

IO_UV

, then the data stream is transmitted to the HS CAN bus. A “low” signal causes a dominant state on the bus and a “high” signal causes a recessive state on the bus. The TxD input pin has an integrated pull-up resistor to V

CC

. If TxD is permanently “low”, for example due to a short circuit to GND, then the TxD time-out feature will block the signal on the TxD input pin (see

Chapter 8.1

). It is not recommended to use a series resistor within the TxD line between transceiver and microcontroller. A series resistor may add delay, which degrades the performance of the transceiver, especially in high data rate applications. The data stream sent from the microcontroller to the

TxD pin of the transceiver is only transmitted to the HS CAN bus in Normal-operating mode. In all other modes the TxD input pin is blocked.

5.4

RxD Pin

RxD is an output pin. The data stream received from the HS CAN bus is displayed on the RxD output pin in

Normal-operating mode, Receive-only mode. It is not recommended to use a series resistor within the RxD

Application Note 9 Rev. 1.1

2016-05-03