MCP2021 datasheet(3/46 Pages) MICROCHIP

3 / 46 page

DS22018E-page 3

MCP2021/2

1.0

DEVICE OVERVIEW

The MCP2021/2 provides a physical interface between

a microcontroller and a LIN half-duplex bus. It is

intended for automotive and industrial applications with

serial bus speeds up to 20 Kbaud.

The MCP2021/2 provides a half-duplex, bidirectional

communications interface between a microcontroller

and the serial network bus. This device will translate

the CMOS/TTL logic levels to LIN level logic, and vice

versa.

The LIN specification 2.0 requires that the transceiver

of all nodes in the system be connected via the LIN pin,

referenced to ground and with a maximum external

termination resistance of 510

Ω from LIN bus to battery

supply. The 510

Ω corresponds to 1 Master and 16

Slave nodes.

The MCP2021-500 provides a +5V 50 mA regulated

power output. The regulator uses a LDO design, is

short-circuit-protected and will turn the regulator output

off if it falls below 3.5V. The MCP2021/2 also includes

thermal shutdown protection. The regulator has been

specifically designed to operate in the automotive

environment and will survive reverse battery connec-

tions, +43V load dump transients and double-battery

jumps. The other members of the MCP2021-330 family

output +3.3V at 50 mA with a turn-off voltage of 2.5V.

(see Section 1.6 “Internal Voltage Regulator”).

1.1

Optional External Protection

1.1.1

REVERSE BATTERY PROTECTION

An external reverse-battery-blocking diode should be

used to provide polarity protection (see Example 1-1).

1.1.2

TRANSIENT VOLTAGE

PROTECTION (LOAD DUMP)

An external 43V transient suppressor (TVS) diode,

between VBB and ground, with a 50

Ω transient

protection resistor (RTP) in series with the battery

supply and the VBB pin serve to protect the device from

power transients (see Example 1-1) and ESD events.

While

this

protection

optional,

it should

considered as good engineering practice.

EQUATION 1-1:

1.2

Internal Protection

1.2.1

ESD PROTECTION

For component-level ESD ratings, please refer to the

maximum operation specifications.

1.2.2

GROUND LOSS PROTECTION

The LIN Bus specification states that the LIN pin must

transition to the recessive state when ground is

disconnected. Therefore, a loss of ground effectively

forces the LIN line to a hi-impedance level.

1.2.3

THERMAL PROTECTION

The thermal protection circuit monitors the die

temperature and is able to shut down the LIN

transmitter and voltage regulator.

There are three causes for a thermal overload. A

thermal shut down can be triggered by any one, or a

combination

of,

the

following

thermal

overload

conditions.

• Voltage regulator overload

• LIN bus output overload

• Increase in die temperature due to increase in

environment temperature

Driving the TXD and checking the RXD pin makes it

possible to determine whether there is a bus contention

(Rx = low, Tx = high) or a thermal overload condition

(Rx = high, Tx = low).

FIGURE 1-1:

THERMAL SHUTDOWN

STATE DIAGRAMS

RTP <= (VBBmin - 5.5) / 250 mA.

5.5V = VUVLO + 1.0V,

250 mA is the peak current at power-on when

VBB = 5.5V

Operation

Mode

Transmitter

Shutdown

LIN bus

Voltage

Shutdown

Regulator

Output

Temp < SHUTDOWNTEMP

shorted

to VBB

Overload

Temp < SHUTDOWN

TEMP

MCP2021 数据表(PDF) 3 Page - Microchip Technology

MCP2021 数据表(HTML) 3 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

数据表下载