DS1819CR-20+T&R datasheet, PDF

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DS1819CR-20+T&R: DescriptionSupervisory Circuits 3.3/5V MicroMonitor; CategoryPower/power management The power supply circuit; File Size144KB，8 Pages; ManufacturerMaxim; Websitehttps://www.maximintegrated.com/en.html; Environmental Compliance

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DS1819CR-20+T&R Overview

Supervisory Circuits 3.3/5V MicroMonitor

DS1819CR-20+T&R Parametric

Parameter Name	Attribute value
Is it lead-free?	Lead free
Is it Rohs certified?	conform to
Maker	Maxim
Parts packaging code	SOT-23
package instruction	LSSOP, TSOP5/6,.11,37
Contacts	5
Reach Compliance Code	compliant
ECCN code	EAR99
Factory Lead Time	1 week
Adjustable threshold	NO
Analog Integrated Circuits - Other Types	POWER SUPPLY SUPPORT CIRCUIT
JESD-30 code	R-PDSO-G5
JESD-609 code	e3
length	2.9 mm
Humidity sensitivity level	1
Number of channels	1
Number of functions	1
Number of terminals	5
Maximum operating temperature	85 °C
Minimum operating temperature	-40 °C
Package body material	PLASTIC/EPOXY
encapsulated code	LSSOP
Encapsulate equivalent code	TSOP5/6,.11,37
Package shape	RECTANGULAR
Package form	SMALL OUTLINE, LOW PROFILE, SHRINK PITCH
Peak Reflow Temperature (Celsius)	260
power supply	1.2/5.5 V
Certification status	Not Qualified
Maximum seat height	1.45 mm
Maximum supply current (Isup)	0.012 mA
Maximum supply voltage (Vsup)	5.5 V
Minimum supply voltage (Vsup)	1.2 V
Nominal supply voltage (Vsup)	3.3 V
surface mount	YES
technology	CMOS
Temperature level	INDUSTRIAL
Terminal surface	Matte Tin (Sn)
Terminal form	GULL WING
Terminal pitch	0.95 mm
Terminal location	DUAL
Maximum time at peak reflow temperature	NOT SPECIFIED
width	1.625 mm

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DS1814/DS1819

5V and 3.3V MicroMonitor

www.maxim-ic.com

FEATURES

Halts and restarts an out-of-control

microprocessor

Holds microprocessor in check during power

transients

Automatically restarts microprocessor after

power failure

Monitors pushbutton for external override

Accurate 5%, 10%, or 20% (3V only)

microprocessor power monitoring

Eliminates the need for discrete components

20% tolerance for use with 3.0V systems

Pin- and function-compatible with the

MAX823/24/25 products

Low cost SOT-23-5 package

Industrial temperature range: -40°C to +85°C

RST

PIN ASSIGNMENT

SOT-23-5 PACKAGE

See Mech. Drawing

PIN DESCRIPTION

DS181xA

RST

2 GND

PBRST

5 VCC

DS181xB

RST

2 GND

3 RST

5 VCC

DS181xC

RST

2 GND

3 RST

PBRST

5 VCC

Active Low Reset Output

Ground

Pushbutton Reset Input

Strobe Input

Power Supply

DEVICE

RST

PBRST

DS181xA

DS181xB

DS181xC

x = "DS1814" for 5V devices

x = "DS1819" for 3V devices

Active Low Reset Output

Ground

Active High Reset Output

Strobe Input

Power Supply

Active Low Reset Output

Ground

Active High Reset Output

Pushbutton Reset Input

Power Supply

DESCRIPTION

The DS1814 5-Volt MicroMonitor and the DS1819 3.3V MicroMonitor monitor three vital conditions for

a microprocessor: power supply, software execution, and external override. First, a precision temperature-

compensated reference and comparator circuit monitor the status of V

. When an out-of-tolerance

condition occurs, an internal power-fail signal is generated which forces the reset(s) to an active state.

When V

returns to an in-tolerance condition, the reset signal is kept in the active state for a minimum of

140ms to allow the power supply and processor to stabilize.

1 of 8

122001

DS1814/DS1819

The DS1814/DS1819 ‘A’ and ‘C’ perform pushbutton reset control. They debounce the pushbutton input

and generate an active reset pulse width of 140ms minimum. The DS1814/9 ‘A’ and ‘B’ versions perform

a watchdog function. The watchdog is an internal timer that forces the reset signals to the active state if

the strobe input does not change state every 1.12 seconds. The watchdog timer function can be disabled

by leaving the watchdog strobe input disconnected.

OPERATION

Power Monitor

The DS1814 detects out-of-tolerance power supply conditions and warns a processor-based system of

impending power failure. When V

falls below a preset level, a comparator outputs the signal

RST

(or

RST).

RST

(or RST) are excellent control signals for a microprocessor, as processing is stopped at the

last possible moment of valid V

. On power-up,

RST

(or RST) are kept active for a minimum of 140ms

to allow the power supply and processor to stabilize.

Pushbutton Reset

The DS1814 ‘A’ and ‘C’ provide an input pin for direct connection to a pushbutton reset (see Figure 2).

The pushbutton reset input requires an active low signal. Internally, this input is debounced and timed

such that a

RST

(or RST) signal of at least 140ms minimum will be generated. The 140ms delay

commences as the pushbutton reset input is released from the low level (see Figure 3).

Watchdog Timer

The DS1814/DS1819 ‘A’ and ‘B’ versions watchdog timer function forces

RST

(and RST) signal(s)

active when the

input is not clocked within the 1.12 second watchdog time-out period. Time-out of

the watchdog starts when

RST

(and RST) become(s) inactive. If a transition occurs on the

input pin

prior to time-out, the watchdog timer is reset and begins to time out again. If the watchdog timer is

allowed to time out, then the reset output(s) will go active for 140ms. The watchdog can be disabled by

floating (or tri-stating) the

input.

The

input can be derived from many microprocessor outputs. The most typical signals used are the

microprocessor data I/O signals and control signals. When the microprocessor functions normally, these

signals would as a matter of routine cause the watchdog to be reset prior to time-out. To guarantee that

the watchdog timer does not time out, a transition must occur at or less than 1.12 seconds. A typical

circuit example is shown in Figure 4. The DS1814/19 watchdog function can be disabled at any time by

tri-starting the strobe input. A sample circuit to disable the watchdog is shown in Figure 6.

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