NCV7420EVB
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3
Functional Description
Overall Functional Description
NCV7420 is designed as a master or slave node for the
LIN communication interface with an integrated 3.3 V or
5 V voltage regulator having a current capability up to
50 mA for supplying any external components
(microcontroller).
NCV7420 contains the LIN transmitter, LIN receiver,
voltage regulator, power-on-reset (POR) circuits and
thermal shutdown (TSD). The LIN transmitter is optimized
for the maximum specified transmission speed of 20 kBaud
with EMC performance due to reduced slew rate of the LIN
output.
The junction temperature is monitored via a thermal
shutdown circuit that switches the LIN transmitter and
voltage regulator off when temperature exceeds the TSD
trigger level.
NCV7420 has four operating states (normal mode, low
slope mode, stand-by mode, and sleep mode) that are
determined by the input signals EN, WAKE, STB, and TxD.
Operating States
NCV7420 provides four operating states, two modes for
normal operation with communication, one stand-by
without communication and one low power mode with very
low current consumption - see Figure 6 and Table 1.
Table 1. MODE SELECTION
Mode Vcc RxD INH LIN transceiver
30 kW on LIN
Normal – Slope
(Note 1)
ON Low = Dominant State
High = Recessive State
High if STB = High during state
transition; Floating otherwise
Normal Slope ON
Normal – Low Slope
(Note 2)
ON Low = Dominant State
High = Recessive State
High if STB = High during state
transition; Floating otherwise
Low Slope ON
Stand-by (Note 3) ON Low after LIN wakeup, high
otherwise (Note 4)
Floating OFF OFF
Sleep OFF Clamped to Vcc (Note 4) Floating OFF OFF
1. The normal slope mode is entered when pin EN goes HIGH while TxD is in HIGH state during EN transition.
2. The low slope mode is entered when pin EN goes HIGH while TxD is in LOW state during EN transition. LIN transmitter gets on only after
TxD returns to high after the state transition.
3. The stand-by mode is entered automatically after power-up.
4. In Stand-by and Sleep mode, the High state is achieved by internal pull-up resistor to VCC.
Figure 6. NCV7420 State Diagram
− V
CC
: On
− LIN TX: Off
− INH: Floating
− Term.: Current Source
− RxD: High/Low
Standby Mode
Power-up Vbb
EN goes from 1 to 0 while STB = 1
EN goes from 0 to 1 while TxD = 1
− V
CC
: On
− LIN TX: On
− INH: High/Floating
− Term.: 30 kW
− RxD: LIN Data
Normal Mode
(Normal Slope)
EN goes from1 to 0 while STB = 0
EN goes from 1 to 0 while STB = 1
EN goes from 0 to 1 while TxD = 0
EN goes from 1 to 0 while STB = 0
Normal Mode
(Low Slope)
− V
CC
: On
− LIN TX: On
− INH: High/Floating
− Term.: 30 kW
− RxD: LIN Data
Sleep Mode
− V
CC
: Off
− LIN TX: Off
− INH: Floating
− Term.: Current Source
− RxD: = VCC
PD20090610.01
Local Wake-up
or LIN Wake-up
Additional details of the NCV7420 operation and parameters can be found in the corresponding datasheet [1].
