DS1819BR-20 datasheet, PDF - EEWORLD Datasheet

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DS1819BR-20: DescriptionPower Supply Management Circuit, Fixed, 1 Channel, PDSO5, SOT-23, 5 PIN; CategoryPower/power management The power supply circuit; File Size111KB，8 Pages; ManufacturerDALLAS; Websitehttp://www.dalsemi.com

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DS1819BR-20 Overview

Power Supply Management Circuit, Fixed, 1 Channel, PDSO5, SOT-23, 5 PIN

DS1819BR-20 Parametric

Parameter Name	Attribute value
Maker	DALLAS
package instruction	SOT-23, 5 PIN
Reach Compliance Code	unknown
Other features	Watchdog Timer, PUSHBUTTON RESET OPTION
Adjustable threshold	NO
Analog Integrated Circuits - Other Types	POWER SUPPLY MANAGEMENT CIRCUIT
JESD-30 code	R-PDSO-G5
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
Package shape	RECTANGULAR
Package form	SMALL OUTLINE
Certification status	Not Qualified
Maximum supply voltage (Vsup)	5.5 V
Minimum supply voltage (Vsup)	1 V
Nominal supply voltage (Vsup)	2.7 V
surface mount	YES
Temperature level	INDUSTRIAL
Terminal form	GULL WING
Terminal location	DUAL
Base Number Matches	1

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DS1814/DS1819

5-Volt and 3.3-Volt MicroMonitor

www.dalsemi.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% (3-volt only)

microprocessor power monitoring

Eliminates the need for discrete components

20% tolerance for use with 3.0-volt systems

Pin- and function-compatible with the

MAX823/24/25 products

Low cost SOT-23-5 package

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

DEVICE

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

RST

PBRST

DS181xA

DS181xB

DS181xC

x = "DS1814" for 5 volt devices

x = "DS1819" for 3 volt 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 3.3-Volt 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 140 ms to allow the power supply and processor to stabilize.

1 of 8

111999

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 140 ms 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 140 ms

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 140 ms minimum will be generated. The 140 ms 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 140 ms. 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.

2 of 8

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