3

FN8111.0

March 28, 2005

PRINCIPLES OF OPERATION

Power On Reset

Application of power to the X40010/11/14/15 activates a

Power On Reset Circuit that pulls the RESET/RESET

pins active. This signal provides several benefits.

– It prevents the system microprocessor from starting to

operate with insufficient voltage.

– It prevents the processor from operating prior to stabili-

zation of the oscillator.

– It allows time for an FPGA to download its configura-

tion prior to initialization of the circuit.

– It prevents communication to the EEPROM, greatly

reducing the likelihood of data corruption on power up.

(X40011) and RESET (X40010) pin allowing the system

to begin operation.

During operation, the X40010/11/14/15 monitors the

falls

below

a

preset

minimum

The

RESET/RESET signal prevents the microprocessor

from operating in a power fail or brownout condition.

The V1FAIL signal remains active until the voltage

Low Voltage V2 Monitoring

The X40010/11/14/15 also monitors a second voltage

level and asserts V2FAIL if the voltage falls below a

ORed with RESET to prevent the microprocessor from

operating in a power fail or brownout condition or used to

interrupt the microprocessor with notification of an

impending power failure. For the X40010/11 the V2FAIL

falling). It also remains active until V2MON returns and

monitors the power supply connected to the V2MON pin.

For the X40014/15 devices, the V2FAIL signal remains

be monitored.

Figure 1. Two Uses of Multiple Voltage Monitoring

68

SCL

Serial Clock. The Serial Clock controls the serial bus timing for data input and output.

71

WDO

WDO Output. WDO is an active LOW, open drain output which goes active whenever the watch-

dog timer goes active.

82

Supply Voltage

Pin

Name

Function

SOIC TSSOP

6–10V

5V

Reg

V2MON

X40011-A

Resistors selected so 3V appears on V2MON when unregulated

supply reaches 6V.

Unreg.

Supply

X40014-C

RESET

V2FAIL

System

Reset

RESET

V2FAIL

System

Reset

Notice: No external components required to monitor two voltages.

1M

1M

V2MON

3.3V

Reg

1.2V

Reg

V2MON

(2.9V)

X40010, X40011, X40014, X40015