DS1818中文资料

1 of 5111999

FEATURES Automatically restarts a microprocessor after power failure

Monitors pushbutton for external override Maintains reset for 150 ms after V CC returns

to an in-tolerance condition

Reduces need for discrete components

Precision temperature-compensated voltage reference and voltage sensor

Accurate 5%, 10% or 20% power monitoring Low-cost TO-92 or space saving surface mount SOT-23 packages available

Efficient open-drain output with internal 5.5 k ?=pull-up resistor

Operating temperature -40°C to +85°C

PIN ASSIGNMENT

PIN DESCRIPTION TO-92

1 RST Active Low Reset Output

2 V CC Power Supply

3 GND Ground

SOT-23

1 RST Active Low Reset Output

2 V CC Power Supply

3 GND Ground

DESCRIPTION

The DS1818 EconoReset uses a precision temperature-compensated reference and comparator circuit to monitor the status of the power supply (V CC ). When an out-of-tolerance condition is detected, an internal power-fail signal is generated which forces reset to the active state. When V CC returns to an in-tolerance condition, the reset signal is kept in the active state for approximately 150 ms to allow the power supply and processor to stabilize.

The DS1818 also monitors a pushbutton on the reset output. If the reset line is pulled low, a reset is generated upon release and the DS1818 output will be held in reset output low for typically 150 ms.

DS1818

3.3V EconoReset with Pushbutton

12

SOT-23 PACKAGE

TO-92 PACKAGE

See Mech.Drawings Section

OPERATION - POWER MONITOR

The DS1818 provides the functions of detecting out-of-tolerance power supply conditions and warning a processor-based system of impending power failures. When V CC is detected as out-of-tolerance, the RST signal is asserted. On power-up, RST is kept active for approximately 150 ms after the power supply has reached the selected tolerance. This allows the power supply and microprocessor to stabilize before RST is released.

BLOCK DIAGRAM (OPEN-DRAIN OUTPUT) Figure 1

APPLICATION EXAMPLE Figure 2

OPERATION - PUSHBUTTON RESET

The DS1818 provides a pushbutton switch for manual reset control. When the DS1818 is not in a reset cycle, a pushbutton reset can be generated by pulling the RST pin low for at least 1 μs. When the pushbutton is held low, the RST is forced active low and will remain active low for about 150 ms after the pushbutton is released. See Figure 2 for an application example and Figure 3 for the timing diagram. TIMING DIAGRAM: PUSHBUTTON RESET Figure 3

TIMING DIAGRAM: POWER-UP Figure 4

TIMING DIAGRAM: POWER-DOWN Figure 5

ABSOLUTE MAXIMUM RATINGS*

Voltage on V CC Pin Relative to Ground -0.5V to +7.0V

Voltage on RST Relative to Ground -0.5V to +5V CC +0.5V Operating Temperature -40°C to +85°C Storage Temperature -55°C to +125°C Soldering Temperature

260°C for 10 seconds

* This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.

RECOMMENDED DC OPERATING CONDITIONS (-40°C to +85°C)

PARAMETER SYMBOL MIN TYP

MAX UNITS NOTES Supply Voltage

V CC

1.0

5.5

V

1

DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; V CC =1.2V to 5.5V)

PARAMETER SYMBOL

MIN TYP

MAX

UNITS NOTES Output Current @ 0.4 V I OL +10

mA 2, 3Voltage Input Low V IL 0.4

V 1Voltage Input High

V IH 0.7*V CC

V 1Operating Current V CC < 5.5V I CC 2835μA 4V CC Trip Point (DS1818-5)V CCTP 2.98 3.06 3.15V 1V CC Trip Point (DS1818-10)V CCTP 2.80 2.88 2.97V 1V CC Trip Point (DS1818-20)V CCTP 2.47 2.55 2.64V 1Internal Pull-up Resistor R P 3.50 5.5

7.5k ?

7

Output Capacitance

C OUT

10

pF

NOTES:

1. All voltages are referenced to ground.

2. Measured with V CC ≥ 2.7V.

3. A 1 k ? external pull-up resistor may be required in some applications for proper operation of the microprocessor reset control circuit.

4. Measured with RST output open.

5. Measured with 2.7V ≤ V CC ≤ 3.3V.

6. t R = 5 μs.

7. V OH and I OH are a function of the value of R P and the associated output load conditions.

8. The t F value is for reference in defining values for t RPD and should not be considered a requirement for proper operation or use of the device.

PART MARKING CODES

“A”, “B”, &“C” represent the device type.

810-DS1810811-DS1811812-DS1812813-DS1813815-DS1815816-DS1816817-DS1817818-DS1818

“D” represents the device tolerance.

A -5%

B -10%

C -15%

D -20%