Analog Integrated Circuit Device Data

12

Freescale Semiconductor

33199

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

The MC33199 is a serial interface circuit used in diagnostic applications. It is the interface between the microcontroller and

the special K and L lines of the ISO diagnostic port. The MC33199 has been designed to meet the «Diagnosis System ISO9141»

specification.

This product description will detail the functionality of the device (see Figure 2, 33199 Simplified Internal Block Diagram). First,

the power supply and reference voltage generator will be discussed, then the paths functions between MCU, K and L lines will

be detailed. A dedicated paragraph will tell about the special functionality of the I1 pin, which allow high Baud rates transmission.

FUNCTIONAL PIN DESCRIPTION

VCC (VCC)

5V typical power supply pin. Typical supply current is less

than 1.5mA.

REF-IN-L (REF-IN-L)

Input reference for C2 comparator. This input can be

connected directly to REF-OUT, with or without a resistor

network, or to an external reference.

REF-IN-K (REF-IN-K)

Input reference for C1 comparator. This input can be

connected directly to REF-OUT, with or without a resistor

network, or to an external reference.

LO (LO)

Output of C2 comparator, normally connected to a micro-

controller I/O. If L input > (REF-IN-L + Hyst/2) then output LO

is in high state. If L< (REF-IN-L - Hyst/2) then output LO is in

low state, output transistor ON.

This pin is an open collector structure. A Pull up resistor

should be added to VCC.

Drive capability of this output is 5mA.

RXD (RXD)

Receive output, normally connected to a microcontroller I/

O.

If DIA input > (REF-IN-L + Hyst/2) then output LO is in high

state.

If DIA < (REF-IN-L - Hyst/2) then output LO is in low state,

output transistor ON. This pin has an internal pull up resistor

to VCC (2Kohm typ). Drive capability of this output is 5mA

TXD (TXD)

Transmission input, is normally connected to a

microcontroller I/O.This pin controls DIA output. If Txd is high,

the output DIA transistor is OFF. If Txd is low the DIA output

transistor is ON.

DIA (DIA)

Input / Output Diagnosis Bus line pin. This pin is an open

collector structure, protected against over current and short

circuit to VBAT (VS). When turning ON (TXD low), this pin will

pull the Bus line to Gnd, the current into DIA will be internally

limited to 60mA typ.

The internal power transistor has a thermal shutdown

circuit, which forces the DIA output OFF in case of over

temperature.

DIA is also the C1 comparator input. It is protected against

both positive and negative over voltage by a 38V zener diode.

This pin exhibits a constant input current of 7.5?A.

GND (GND)

Gnd reference for the entire device.

I1 (I1)

Bus source current pin. It is normally tied to DIA pin and to

the Bus line.

At static HIGH or LOW level Txd, the current source I1

delivers a current of 3mA (typ). Only during LOW to HIGH

transition, does this current increase to a higher value in

order to charge the key line capacitor (Cl<4nF) in a short time

(see fig 3 and 4).

L (L)

Input for C2 comparator. This pin is protected against both

positive and negative over voltage by a 38V zener diode.

This L line is a second independent input. It can be used

for wake up sequence in ISO diagnosis or as an additional

input bus line.

This pin exhibits a constant input current of 7.5

µΑ.

VS (VS)

12V typical, or Vbat supply pin for the device. This pin is

protected against over voltage transients.

REF-OUT (REF-OUT)

Internal reference voltage generator output pin. Its value

depends on Vs (Vbat) values. This output can be directly

connected to REF-IN L and REF-IN-K, or through a resistor

network. Maximum current capability is 50

µΑ.