X40420 datasheet(4/25 Pages) INTERSIL

Numer części	X40420

Szczegółowy opis	Dual Voltage Monitor with Integrated CPU Supervisor and System Battery Switch

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Producent	INTERSIL [Intersil Corporation]

Strona internetowa	http://www.intersil.com/cda/home

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March 28, 2005

PRINCIPLES OF OPERATION

Power-on Reset

Applying power to the X40420/21 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 sta-

bilization 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.

When VCC exceeds the device VTRIP1 threshold value

for tPURST (selectable) the circuit releases the RESET

(X40421) and RESET (X40420) pin allowing the system

to begin operation.

Figure 1. Connecting a Manual Reset Push-Button

Manual Reset

By connecting a push-button directly from MR to

ground, the designer adds manual system reset capa-

bility. The MR pin is LOW while the push-button is

closed and RESET/RESET pin remains LOW for

tPURST or till the push-button is released and for tPURST

thereafter. A weak pull up resistor is connected to the

MR pin.

Low Voltage V1 Monitoring

During operation, the X40420/21 monitors the VCC

level and asserts RESET if supply voltage falls below

a preset minimum VTRIP1. The RESET signal prevents

the microprocessor from operating in a power fail or

brownout condition. The V1FAIL signal remains active

until the voltage drops below 1V. It also remains active

until VCC returns and exceeds VTRIP1 for tPURST.

Low Voltage V2 Monitoring

The X40420/21 also monitors a second voltage level and

asserts V2FAIL if the voltage falls below a preset mini-

mum VTRIP2. The V2FAIL signal is either 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. The V2FAIL signal remains active until the VCC

drops below 1V (VCC falling). It also remains active until

V2MON returns and exceeds VTRIP2.

V2MON voltage monitor is powered by VOUT. If VCC

and VBATT go away, V2MON cannot be monitored.

Figure 2. Two Uses of Multiple Voltage Monitoring

WATCHDOG TIMER

The Watchdog Timer circuit monitors the microproces-

sor activity by monitoring the SDA and SCL pins. A

standard read or write sequence to any slave address

byte restarts the watchdog timer and prevents the

WDO signal to go active. A minimum sequence to

reset the watchdog timer requires four microprocessor

instructions namely, a Start, Clock Low, Clock High

and Stop. The state of two nonvolatile control bits in

the Status Register determine the watchdog timer

period. The microprocessor can change these watch-

dog bits by writing to the X40420/21 control register.

MR

System

Reset

Manual

Reset

X40420/21

RESET

Unreg.

Supply

VCC

5V

Reg

V2MON

X40420

Resistors selected so 3V appears on V2MON when unregulated

supply reaches 6V.

Unreg.

Supply

VCC

X40421

RESET

V2FAIL

System

VOUT

Reset

RESET

V2FAIL

VOUT

System

Reset

Notice: No external components required to monitor two voltages.

R

V2MON

5V

Reg

3V

Reg

X40420, X40421

Podobny numer części - X40420

Producent	Numer części	Arkusz danych	Szczegółowy opis
Xicor Inc.	X40420	156Kb / 25P	Dual Voltage Monitor with Integrated CPU Supervisor and System Battery Switch
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Renesas Technology Corp	X40420S14-A	985Kb / 25P	4kbit EEPROM Dual Voltage Monitor with Integrated CPU Supervisor and System Battery Switch May 25, 2006
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Producent	Numer części	Arkusz danych	Szczegółowy opis
Xicor Inc.	X40420	156Kb / 25P	Dual Voltage Monitor with Integrated CPU Supervisor and System Battery Switch
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Intersil Corporation	X40020	356Kb / 24P	Dual Voltage Monitor with Integrated CPU Supervisor and System Battery Switch
Renesas Technology Corp	X40420	985Kb / 25P	4kbit EEPROM Dual Voltage Monitor with Integrated CPU Supervisor and System Battery Switch May 25, 2006
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Xicor Inc.	X40010	124Kb / 25P	Dual Voltage Monitor with Integrated CPU Supervisor
Intersil Corporation	X55060	375Kb / 23P	Dual Voltage Monitor with Integrated System Battery Switch and EEPROM
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