MCP2025-500ESLASHP datasheet(7/38 Pages) MICROCHIP

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 2012-2014 Microchip Technology Inc.

DS20002306B-page 7

MCP2025

1.2.7

RESET

Reset output pin. This is an open-drain output pin. It

indicates the internal voltage has reached a valid,

stable level. As long as the internal voltage is valid

(above 0.8 VREG), this pin will present high impedance;

otherwise, the RESET pin switches to ground.

1.2.8

POSITIVE SUPPLY VOLTAGE

REGULATOR OUTPUT (VREG)

Positive Supply Voltage Regulator Output pin. An

on-chip Low Dropout Regulator (LDO) gives +5.0 or

+3.3V at 70 mA regulated voltage on this pin.

1.2.9

EXPOSED THERMAL PAD (EP)

There is an internal electrical connection between the

Exposed Thermal Pad (EP) and the VSS pin; they must

be connected to the same potential on the Printed

Circuit Board (PCB).

This pad can be connected to a PCB ground plane to

provide a larger heat sink. This improves the package

thermal resistance (

JA).

1.3

Fail-Safe Features

1.3.1

GENERAL FAIL-SAFE FEATURES

• An internal pull-down resistor on the CS/LWAKE

pin disables the transmitter if the pin is floating.

• An internal pull-up resistor on the TXD pin places

TXD in high and the LBUS in recessive if the TXD

pin is floating.

• High-Impedance and low-leakage current on LBUS

during loss of power or ground.

• The current limit on LBUS protects the transceiver

from being damaged if the pin is shorted to VBB.

1.3.2

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 shutdown 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

The recovery time from the thermal shutdown is equal

to adequate cooling time.

Driving the TXD and checking the RXD pin make it

possible to determine whether there is a bus contention

(TXD = high, RXD = low) or a thermal overload

condition (TXD =low, RXD = high).

FIGURE 1-2:

THERMAL SHUTDOWN

STATE DIAGRAMS

1.3.3

TXD/LBUS TIME-OUT TIMER

The LIN bus can be driven to a dominant level, either

from the TXD pin or externally. An internal timer

deactivates the LBUS transmitter if a dominant status

(low) on the LIN bus lasts longer than Bus Dominant

Time-Out

Time,

tTO(LIN)

(approximately

20 milliseconds). At the same time, the RXD output is

put in recessive (high) and the internal pull-up resistor

between LBUS and VBB is disconnected. The timer is

reset on any recessive LBUS status or POR mode. The

recessive status on LBUS can be caused either by the

bus being externally pulled-up or by the TXD pin being

returned high.

1.4

Internal Voltage Regulator

The MCP2025 has a positive regulator capable of

supplying +5.00 or +3.30 VDC ±3% at up to 70 mA of

load current over the entire operating temperature

range of -40°C to +125°C. The regulator uses an LDO

design, is short-circuit-protected and will turn the

regulator output off if its output falls below the shutdown

voltage threshold, VSD.

With a load current of 70 mA, the minimum

input-to-output voltage differential required for the

output to remain in regulation is typically +0.5V (+1V

maximum over the full operating temperature range).

Quiescent current is less than 100 µA with a full 70 mA

load current

when

the

input-to-output

voltage

differential is greater than +3.00V.

Regarding the correlation between VBB, VREG and IDD,

please refer to Figures 1-4 and 1-5. When the input

voltage (VBB) drops below the differential needed to

provide stable regulation, the voltage regulator output,

VREG, will track the input down to approximately VOFF,

at which point the regulator will turn off the output. This

will allow PIC® microcontrollers with internal POR

circuits to generate a clean arming of the POR trip

point. The MCP2025 will then monitor VBB and turn on

the regulator when VBB is above the threshold of

regulator turn-on voltage, VON.

In Power-Down mode, the VBB monitor is turned off.

Voltage

Regulator

Shutdown

Operation

Mode

Transmitter

Shutdown

Output

Overload

LIN Bus

Shorted to

VBB

Temp < SHUTDOWNTEMP Temp < SHUTDOWNTEMP

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