33399 datasheet(10/19 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33399

FUNCTIONAL DESCRIPTION

TIMING DIAGRAMS

FUNCTIONAL DESCRIPTION

INTRODUCTION

The 33399 is a Physical Layer component dedicated to

automotive LIN sub-bus applications.

The 33399 features include speed communication from

1.0 kbps to 20 kbps, up to 60 kbps for Programming Mode,

and active bus waveshaping to minimize radiated emission.

The device offers three different wake-up capabilities:

wake-up from LIN bus, wake-up from the MCU command,

and dedicated high voltage wake-up input.

The INH output may be used to control an external voltage

regulator.

FUNCTIONAL PIN DESCRIPTION

POWER SUPPLY PIN (VSUP)

The VSUP power supply pin is connected to a battery

through a serial diode for reverse battery protection. The DC

operating voltage is from 7.0 V to 27 V. This pin sustains

standard automotive voltage conditions such as 27 V DC

during jump-start conditions and 40 V during load dump. To

avoid a false bus message, an undervoltage reset circuitry

disables the transmission path (from TXD to LIN) when VSUP

falls below 7.0 V. Supply current in the Sleep mode is

typically 20

µA.

GROUND PIN (GND)

In case of a ground disconnection at the module level, the

33399 does not have significant current consumption on the

LIN bus pin when in the recessive state. (Less than 100 µA is

sourced from LIN bus pin, which creates 100 mV drop

voltage from the 1.0 k

Ω LIN bus pullup resistor.) For the

dominant state, the pullup resistor should always be active.

The 33399 handles a ground shift up to 3.0 V when

VSUP > 9.0 V. Below 9.0 V VSUP, a ground shift can reduce

VSUP value below the minimum VSUP operation of 7.0 V.

LIN BUS PIN (LIN)

The LIN bus pin represents the single-wire bus transmitter

and receiver.

Transmitter Characteristics

The LIN driver is a low-side MOSFET with internal current

limitation and thermal shutdown. An internal pullup resistor

with a serial diode structure is integrated so no external

pullup components are required for the application in a slave

node. An additional pullup resistor of 1.0 k

Ω must be added

when the device is used in the master node.

Voltage can go from -18 V to 40 V without current other

than the pullup resistance. The LIN pin exhibits no reverse

current from the LIN bus line to VSUP, even in the event of

GND shift or VPWR disconnection. LIN thresholds are

compatible with the LIN protocol specification.

The fall time from recessive to dominant and the rise time

from dominant to recessive are controlled to typically

2.0 V/µs. The symmetry between rise and fall time is also

guaranteed.

When going from dominant to recessive, the bus

impedance parasitic capacitor must be charged up to VSUP.

This charge-up is achieved by the total system pullup current

resistors. In order to guarantee that the rise time is within

specification, maximum bus capacitance should not exceed

10 nF with bus total pullup resistance less than 1.0 k

Ω.

Receiver Characteristics

The receiver thresholds are ratiometric with the device

supply pin. Typical threshold is 50%, with a hysteresis

between 5% and 10% of VSUP.

DATA INPUT PIN (TXD)

The TXD input pin is the MCU interface that controls the

state of the LIN output. When TXD is LOW, LIN output is

LOW; when TXD is HIGH, the LIN output transistor is turned

OFF.

This pin has an internal 5.0 V internal pullup current

source to set the bus in a recessive state in case the MCU is

not able to control it; for instance, during system power-up/

power-down. During the Sleep mode, the pullup current

source is turned OFF.

DATA OUTPUT PIN (RXD)

The RXD output pin is the MCU interface that reports the

state of the LIN bus voltage. LIN HIGH (recessive) is reported

by a high level on RXD; LIN LOW (dominant) is reported by a

low voltage on RXD. RXD output structure is a CMOS-type

push-pull output stage.

ENABLE INPUT PIN (EN)

The EN pin controls the operation mode of the interface. If

EN = logic [1], the interface is in normal mode, with the

transmission path from TXD to LIN and from LIN to RXD both

active. If EN = logic [0], the device is in Sleep mode or low

power mode, and no transmission is possible.

In Sleep mode, the LIN bus pin is held at VSUP through the

bus pullup resistors and pullup current sources. The device

can transmit only after being awakened. Refer to the INHIBIT

OUTPUT PIN (INH) description on page 11.

During Sleep mode, the device is still supplied from the

battery voltage (through VSUP pin). Supply current is 20 µA

typical. Setting the EN pin to LOW will turn the INH to high

impedance. The EN pin has an internal 20 µA pulldown

current source to ensure the device is in Sleep mode if EN

floats.

33399 Datasheet(PDF) 10 Page - Freescale Semiconductor, Inc

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